@article{Kondra2024,

title = {Coherence Manipulation in Asymmetry and Thermodynamics},

author = {Tulja Varun Kondra and Ray Ganardi and Alexander Streltsov},

doi = {10.1103/physrevlett.132.200201},

issn = {1079-7114},

year  = {2024},

date = {2024-05-00},

urldate = {2024-05-00},

journal = {Phys. Rev. Lett.},

volume = {132},

number = {200201},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Halder2024,

title = {Identifying the value of a random variable unambiguously: Quantum versus classical approaches},

author = {Saronath Halder and Alexander Streltsov and Manik Banik},

doi = {10.1103/physreva.109.052608},

issn = {2469-9934},

year  = {2024},

date = {2024-05-00},

urldate = {2024-05-00},

journal = {Phys. Rev. A},

volume = {109},

number = {052608},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lami2024,

title = {No-go theorem for entanglement distillation using catalysis},

author = {Ludovico Lami and Bartosz Regula and Alexander Streltsov},

doi = {10.1103/physreva.109.l050401},

issn = {2469-9934},

year  = {2024},

date = {2024-05-00},

urldate = {2024-05-00},

journal = {Phys. Rev. A},

volume = {109},

number = {L050401},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jarzyna2024,

title = {Photon information efficiency limits in deep-space optical communications},

author = {Marcin Jarzyna and Ludwig Kunz and Wojciech Zwoliński and Michał Jachura and Konrad Banaszek},

doi = {10.1117/1.oe.63.4.041209},

issn = {0091-3286},

year  = {2024},

date = {2024-04-01},

journal = {Opt. Eng.},

volume = {63},

number = {04},

publisher = {SPIE-Intl Soc Optical Eng},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Notarnicola2024,

title = {Continuous-variable quantum key distribution over multispan links employing phase-insensitive and phase-sensitive amplifiers},

author = {M N Notarnicola and F Cieciuch and M Jarzyna},

doi = {10.1088/1367-2630/ad3774},

issn = {1367-2630},

year  = {2024},

date = {2024-04-01},

journal = {New J. Phys.},

volume = {26},

number = {4},

publisher = {IOP Publishing},

abstract = {Abstract

               Transmission losses through optical fibers are one of the main obstacles preventing both long-distance quantum communications and continuous-variable quantum key distribution. Optical amplification provides a tool to obtain, at least partially, signal restoration. In this work, we address a key distribution protocol over a multi-span link employing either phase-insensitive (PIA) or phase-sensitive (PSA) amplifiers, considering Gaussian modulation of coherent states followed by homodyne detection at the receiver’s side. We perform the security analysis under both unconditional and conditional security frameworks by assuming in the latter case only a single span of the whole communication link to be untrusted. We compare the resulting key generation rate (KGR) for both kinds of amplified links with the no-amplifier protocol, identifying the enhancement introduced by optical amplification. We prove an increase in the KGR for the PSA link in the unconditional scenario and for both PSA and PIA in the conditional security setting depending on position of the attack and the measured quadrature.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Datta2024,

title = {Entanglement catalysis for quantum states and noisy channels},

author = {Chandan Datta and Tulja Varun Kondra and Marek Miller and Alexander Streltsov},

doi = {10.22331/q-2024-03-20-1290},

issn = {2521-327X},

year  = {2024},

date = {2024-03-20},

urldate = {2024-03-20},

journal = {Quantum},

volume = {8},

number = {1290},

publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},

abstract = {<jats:p>Many applications of the emerging quantum technologies, such as quantum teleportation and quantum key distribution, require singlets, maximally entangled states of two quantum bits. It is thus of utmost importance to develop optimal procedures for establishing singlets between remote parties. As has been shown very recently, singlets can be obtained from other quantum states by using a quantum catalyst, an entangled quantum system which is not changed in the procedure. In this work we take this idea further, investigating properties of entanglement catalysis and its role for quantum communication. For transformations between bipartite pure states, we prove the existence of a universal catalyst, which can enable all possible transformations in this setup. We demonstrate the advantage of catalysis in asymptotic settings, going beyond the typical assumption of independent and identically distributed systems. We further develop methods to estimate the number of singlets which can be established via a noisy quantum channel when assisted by entangled catalysts. For various types of quantum channels our results lead to optimal protocols, allowing to establish the maximal number of singlets with a single use of the channel.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2024b,

title = {Multiparameter quantum sensing and magnetic communication with a hybrid dc and rf optically pumped magnetometer},

author = {Michał Lipka and Aleksandra Sierant and Charikleia Troullinou and Morgan W. Mitchell},

doi = {10.1103/physrevapplied.21.034054},

issn = {2331-7019},

year  = {2024},

date = {2024-03-00},

urldate = {2024-03-00},

journal = {Phys. Rev. Applied},

volume = {21},

number = {034054},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Naseri2024,

title = {Quantum speed limits for change of basis},

author = {Moein Naseri and Chiara Macchiavello and Dagmar Bruß and Paweł Horodecki and Alexander Streltsov},

doi = {10.1088/1367-2630/ad25a5},

issn = {1367-2630},

year  = {2024},

date = {2024-02-01},

urldate = {2024-02-01},

journal = {New J. Phys.},

volume = {26},

number = {023052},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>Quantum speed limits provide ultimate bounds on the time required to transform one quantum state into another. Here, we introduce a novel notion of quantum speed limits for collections of quantum states, investigating the time for converting a basis of states into an unbiased one as well as basis permutation. Establishing an unbiased basis, we provide tight bounds for the systems of dimension smaller than 5, and general bounds for multi-qubit systems and the Hilbert space dimension <jats:italic>d</jats:italic>. For two-qubit systems, we show that the fastest transformation implements two Hadamards and a swap of the qubits simultaneously. We further prove that for qutrit systems the evolution time depends on the particular type of the unbiased basis. Permuting a basis, we obtain the exact expression for the Hilbert space of dimension <jats:italic>d</jats:italic>. We also investigate speed limits for coherence generation, providing the minimal time to establish a certain amount of coherence with a unitary evolution.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Miller2024,

title = {Power of noisy quantum states and the advantage of resource dilution},

author = {Marek Miller and Manfredi Scalici and Marco Fellous-Asiani and Alexander Streltsov},

doi = {10.1103/physreva.109.022404},

issn = {2469-9934},

year  = {2024},

date = {2024-02-00},

urldate = {2024-02-00},

journal = {Phys. Rev. A},

volume = {109},

number = {022404},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jastrzębski2024,

title = {Spectrum-to-position mapping via programmable spatial dispersion implemented in an optical quantum memory},

author = {Marcin Jastrzębski and Stanisław Kurzyna and Bartosz Niewelt and Mateusz Mazelanik and Wojciech Wasilewski and Michał Parniak},

doi = {10.1103/physreva.109.012418},

issn = {2469-9934},

year  = {2024},

date = {2024-01-00},

urldate = {2024-01-00},

journal = {Phys. Rev. A},

volume = {109},

number = {012418},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Borówka2023,

title = {Continuous wideband microwave-to-optical converter based on room-temperature Rydberg atoms},

author = {Sebastian Borówka and Uliana Pylypenko and Mateusz Mazelanik and Michał Parniak},

doi = {10.1038/s41566-023-01295-w},

issn = {1749-4893},

year  = {2024},

date = {2024-01-00},

journal = {Nat. Photon.},

volume = {18},

number = {1},

pages = {32--38},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractThe coupling of microwave and optical systems presents an immense challenge due to the natural incompatibility of energies, but potential applications range from optical interconnects for quantum computers to next-generation quantum microwave sensors, detectors and coherent imagers. Several of the engineered platforms that have emerged are constrained by specific conditions, such as cryogenic environments, impulse protocols or narrowband fields. Here we employ Rydberg atoms that allow the wideband coupling of optical and microwave photons at room temperature with the use of a modest set-up. We present continuous-wave conversion of a 13.9 GHz field to a near-infrared optical signal using an ensemble of Rydberg atoms via a free-space six-wave mixing process designed to minimize noise interference from any nearby frequencies. The Rydberg photonic converter exhibits a conversion dynamic range of 57 dB and a wide conversion bandwidth of 16 MHz. Using photon counting, we demonstrate the readout of photons of free-space 300 K thermal background radiation at 1.59 nV cm−1 rad−1/2 s−1/2 (3.98 nV cm−1 Hz−1/2) with a sensitivity down to 3.8 K of noise-equivalent temperature, allowing us to observe Hanbury Brown and Twiss interference of microwave photons.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Krokosz2024,

title = {Beating the spectroscopic Rayleigh limit via post-processed heterodyne detection},

author = {Wiktor Krokosz and Mateusz Mazelanik and Michał Lipka and Marcin Jarzyna and Wojciech Wasilewski and Konrad Banaszek and Michał Parniak},

doi = {10.1364/ol.514659},

issn = {1539-4794},

year  = {2024},

date = {2024-00-00},

urldate = {2024-00-00},

journal = {Opt. Lett.},

volume = {49},

number = {4},

pages = {1001-1004},

publisher = {Optica Publishing Group},

abstract = {<jats:p>Quantum-inspired superresolution methods surpass the Rayleigh limit in imaging, or the analogous Fourier limit in spectroscopy. This is achieved by carefully extracting the information carried in the emitted optical field by engineered measurements. An alternative to complex experimental setups is to use simple homodyne detection and customized data analysis. We experimentally investigate this method in the time-frequency domain and demonstrate the spectroscopic superresolution for two distinct types of light sources: thermal and phase-averaged coherent states. The experimental results are backed by theoretical predictions based on estimation theory.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2024,

title = {Ultrafast electro-optic time-frequency fractional Fourier imaging at the single-photon level},

author = {Michał Lipka and Michał Parniak},

doi = {10.1364/oe.507911},

issn = {1094-4087},

year  = {2024},

date = {2024-00-00},

urldate = {2024-00-00},

journal = {Opt. Express},

volume = {32},

number = {6},

pages = {9573-9588},

publisher = {Optica Publishing Group},

abstract = {<jats:p>The Fractional Fourier Transform (FRT) corresponds to an arbitrary-angle rotation in the phase space, e.g., the time-frequency (TF) space, and generalizes the fundamentally important Fourier Transform. FRT applications range from classical signal processing (e.g., time-correlated noise optimal filtering) to emerging quantum technologies (e.g., super-resolution TF sensing) which rely on or benefit from coherent low-noise TF operations. Here a versatile low-noise single-photon-compatible implementation of the FRT is presented. Optical TF FRT can be synthesized as a series of a spectral disperser, a time-lens, and another spectral disperser. Relying on the state-of-the-art electro-optic modulators (EOM) for the time-lens, our method avoids added noise inherent to the alternatives based on non-linear optical interactions (such as wave-mixing, cross-phase modulation, or parametric processes). Precise control of the EOM-driving radio-frequency signal enables fast all-electronic control of the FRT angle. In the experiment, we demonstrate FRT angles of up to 1.63 rad for pairs of coherent temporally separated 11.5 ps-wide pulses in the near-infrared (800 nm). We observe a good agreement between the simulated and measured output spectra in the bright-light and single-photon-level regimes, and for a range of pulse separations (20 ps to 26.7 ps). Furthermore, a tradeoff is established between the maximal FRT angle and optical bandwidth, with the current setup accommodating up to 248 GHz of bandwidth. With the ongoing progress in EOM on-chip integration, we envisage excellent scalability and vast applications in all-optical TF processing both in the classical and quantum regimes.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mazelanik2023,

title = {Coherent optical two-photon resonance tomographic imaging in three dimensions},

author = {Mateusz Mazelanik and Adam Leszczyński and Tomasz Szawełło and Michał Parniak},

doi = {10.1038/s42005-023-01284-z},

issn = {2399-3650},

year  = {2023},

date = {2023-12-00},

urldate = {2023-12-00},

journal = {Commun Phys},

volume = {6},

number = {165},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:title>Abstract</jats:title><jats:p>Magnetic resonance imaging is a three-dimensional imaging technique, where a gradient of the magnetic field is used to interrogate spin resonances with spatial resolution. The application of this technique to probe the coherence of atoms with good three-dimensional resolution is a challenging application. We propose and demonstrate an optical method to probe spin resonances via a two-photon Raman transition, reconstructing the 3D-structure of an atomic ensemble’s coherence, which is itself subject to external fields. Our method relies on a single time-and-space resolved heterodyne measurement, allowing the reconstruction of a complex 3D coherence profile. Owing to the optical interface, we reach a tomographic image resolution of 14 × 14 × 36 <jats:italic>μ</jats:italic>m<jats:sup>3</jats:sup>. The technique allows to probe any transparent medium with a resonance structure and provides a robust diagnostic tool for atom-based quantum information protocols. As such, it is a viable technique for application to magnetometry, electrometry, and imaging of electromagnetic fields.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Meraki2023,

title = {Zero-field optical magnetometer based on spin alignment},

author = {A. Meraki and L. Elson and N. Ho and A. Akbar and M. Koźbiał and J. Kołodyński and K. Jensen},

doi = {10.1103/physreva.108.062610},

issn = {2469-9934},

year  = {2023},

date = {2023-12-00},

urldate = {2023-12-00},

journal = {Phys. Rev. A},

volume = {108},

number = {062610},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Datta2023b,

title = {Catalysis of entanglement and other quantum resources},

author = {Chandan Datta and Tulja Varun Kondra and Marek Miller and Alexander Streltsov},

doi = {10.1088/1361-6633/acfbec},

issn = {1361-6633},

year  = {2023},

date = {2023-11-01},

journal = {Rep. Prog. Phys.},

volume = {86},

number = {11},

publisher = {IOP Publishing},

abstract = {Abstract

               In chemistry, a catalyst is a substance which enables a chemical reaction or increases its rate, while remaining unchanged in the process. Instead of chemical reactions, quantum catalysis enhances our ability to convert quantum states into each other under physical constraints. The nature of the constraints depends on the problem under study and can arise, e.g. from energy preservation. This article reviews the most recent developments in quantum catalysis and gives a historical overview of this research direction. We focus on the catalysis of quantum entanglement and coherence, and also discuss this phenomenon in quantum thermodynamics and general quantum resource theories. We review applications of quantum catalysis and also discuss the recent efforts on universal catalysis, where the quantum state of the catalyst does not depend on the states to be transformed. Catalytic embezzling is also considered, a phenomenon that occurs if the catalyst’s state can change in the transition.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Naikoo2023,

title = {Multiparameter Estimation Perspective on Non-Hermitian Singularity-Enhanced Sensing},

author = {Javid Naikoo and Ravindra W. Chhajlany and Jan Kołodyński},

doi = {10.1103/physrevlett.131.220801},

issn = {1079-7114},

year  = {2023},

date = {2023-11-00},

urldate = {2023-11-00},

journal = {Phys. Rev. Lett.},

volume = {131},

number = {220801},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Notarnicola2023,

title = {Optimizing state-discrimination receivers for continuous-variable quantum key distribution over a wiretap channel},

author = {M N Notarnicola and M Jarzyna and S Olivares and K Banaszek},

doi = {10.1088/1367-2630/acfd50},

issn = {1367-2630},

year  = {2023},

date = {2023-10-01},

urldate = {2023-10-01},

journal = {New J. Phys.},

volume = {25},

number = {103014},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title><jats:p>We address a continuous-variable quantum key distribution protocol employing quaternary phase-shift-keying of coherent states and a non-Gaussian measurement inspired by quantum receivers minimizing the error probability in a quantum-state-discrimination scenario. We consider a pure-loss quantum wiretap channel, in which a possible eavesdropper is limited to collect the sole channel losses. We perform a characterization of state-discrimination receivers and design an optimized receiver maximizing the asymptotic secure key rate (SKR), namely the key-rate optimized receiver (KOR), comparing its performance with respect to the pretty good measurement and the heterodyne-based protocol. We show that the KOR increases the SKR for metropolitan-network distances. Finally, we also investigate the implementations of feasible schemes, such as the displacement feed-forward receiver, obtaining an increase in the SKR in particular regimes.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Łukanowski2023,

title = {Quantum Limits on the Capacity of Multispan Links With Phase-Sensitive Amplification},

author = {Karol Łukanowski and Konrad Banaszek and Marcin Jarzyna},

doi = {10.1109/jlt.2023.3256585},

issn = {1558-2213},

year  = {2023},

date = {2023-08-01},

journal = {J. Lightwave Technol.},

volume = {41},

number = {15},

pages = {5017--5025},

publisher = {Institute of Electrical and Electronics Engineers (IEEE)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Goswami2023,

title = {Information locking and its resource-efficient extraction},

author = {Suchetana Goswami and Saronath Halder},

doi = {10.1103/physreva.108.012405},

issn = {2469-9934},

year  = {2023},

date = {2023-07-00},

urldate = {2023-07-00},

journal = {Phys. Rev. A},

volume = {108},

number = {012405},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jarzyna2023,

title = {Quantum Pulse Gate Attack on IM/DD Optical Key Distribution Exploiting Symbol Shape Distortion},

author = {Marcin Jarzyna and Michał Jachura and Konrad Banaszek},

doi = {10.1109/lcomm.2023.3273305},

issn = {1558-2558},

year  = {2023},

date = {2023-07-00},

journal = {IEEE Commun. Lett.},

volume = {27},

number = {7},

pages = {1699--1703},

publisher = {Institute of Electrical and Electronics Engineers (IEEE)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Datta2023,

title = {Is There a Finite Complete Set of Monotones in Any Quantum Resource Theory?},

author = {Chandan Datta and Ray Ganardi and Tulja Varun Kondra and Alexander Streltsov},

doi = {10.1103/physrevlett.130.240204},

issn = {1079-7114},

year  = {2023},

date = {2023-06-00},

urldate = {2023-06-00},

journal = {Phys. Rev. Lett.},

volume = {130},

number = {240204},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Niewelt2023,

title = {Experimental Implementation of the Optical Fractional Fourier Transform in the Time-Frequency Domain},

author = {Bartosz Niewelt and Marcin Jastrzębski and Stanisław Kurzyna and Jan Nowosielski and Wojciech Wasilewski and Mateusz Mazelanik and Michał Parniak},

doi = {10.1103/physrevlett.130.240801},

issn = {1079-7114},

year  = {2023},

date = {2023-06-00},

urldate = {2023-06-00},

journal = {Phys. Rev. Lett.},

volume = {130},

number = {240801},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fellous-Asiani2023,

title = {Comparing the quantum switch and its simulations with energetically constrained operations},

author = {Marco Fellous-Asiani and Raphaël Mothe and Léa Bresque and Hippolyte Dourdent and Patrice A. Camati and Alastair A. Abbott and Alexia Auffèves and Cyril Branciard},

doi = {10.1103/physrevresearch.5.023111},

issn = {2643-1564},

year  = {2023},

date = {2023-05-00},

urldate = {2023-05-00},

journal = {Phys. Rev. Research},

volume = {5},

number = {023111},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kumari2023,

title = {Interplay of nonlocality and incompatibility breaking qubit channels},

author = {Swati Kumari and Javid Naikoo and Sibasish Ghosh and A. K. Pan},

doi = {10.1103/physreva.107.022201},

issn = {2469-9934},

year  = {2023},

date = {2023-02-00},

urldate = {2023-02-00},

journal = {Phys. Rev. A},

volume = {107},

number = {022201},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Krisnanda2022,

title = {Correlations and energy in mediated dynamics},

author = {Tanjung Krisnanda and Su-Yong Lee and Changsuk Noh and Jaewan Kim and Alexander Streltsov and Timothy C H Liew and Tomasz Paterek},

doi = {10.1088/1367-2630/aca9ef},

issn = {1367-2630},

year  = {2022},

date = {2022-12-01},

urldate = {2022-12-01},

journal = {New J. Phys.},

volume = {24},

number = {123025},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>The minimum time required for a quantum system to evolve to a distinguishable state is set by the quantum speed limit, and consequently influences the change of quantum correlations and other physical properties. Here we study the time required to maximally entangle two principal systems interacting either directly or via a mediating ancillary system, under the same energy constraints. The direct interactions are proved to provide the fastest way to entangle the principal systems, but it turns out that there exist mediated dynamics that are just as fast. We show that this can only happen if the mediator is initially correlated with the principal systems. These correlations can be fully classical and can remain classical during the entangling process. The final message is that correlations save energy: one has to supply extra energy if maximal entanglement across the principal systems is to be obtained as fast as with an initially correlated mediator.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Naseri2022,

title = {Entanglement and coherence in the Bernstein-Vazirani algorithm},

author = {Moein Naseri and Tulja Varun Kondra and Suchetana Goswami and Marco Fellous-Asiani and Alexander Streltsov},

doi = {10.1103/physreva.106.062429},

issn = {2469-9934},

year  = {2022},

date = {2022-12-00},

urldate = {2022-12-00},

journal = {Phys. Rev. A},

volume = {106},

number = {062429},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Len2022,

title = {Quantum metrology with imperfect measurements},

author = {Yink Loong Len and Tuvia Gefen and Alex Retzker and Jan Kołodyński},

doi = {10.1038/s41467-022-33563-8},

issn = {2041-1723},

year  = {2022},

date = {2022-12-00},

urldate = {2022-12-00},

journal = {Nat Commun},

volume = {13},

number = {6971},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:title>Abstract</jats:title><jats:p>The impact of measurement imperfections on quantum metrology protocols has not been approached in a systematic manner so far. In this work, we tackle this issue by generalising firstly the notion of quantum Fisher information to account for noisy detection, and propose tractable methods allowing for its approximate evaluation. We then show that in canonical scenarios involving <jats:italic>N</jats:italic> probes with local measurements undergoing readout noise, the optimal sensitivity depends crucially on the control operations allowed to counterbalance the measurement imperfections—with global control operations, the ideal sensitivity (e.g., the Heisenberg scaling) can always be recovered in the asymptotic <jats:italic>N</jats:italic> limit, while with local control operations the quantum-enhancement of sensitivity is constrained to a constant factor. We illustrate our findings with an example of NV-centre magnetometry, as well as schemes involving spin-1/2 probes with bit-flip errors affecting their two-outcome measurements, for which we find the input states and control unitary operations sufficient to attain the ultimate asymptotic precision.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mazelanik2022,

title = {Optical-domain spectral super-resolution via a quantum-memory-based time-frequency processor},

author = {Mateusz Mazelanik and Adam Leszczyński and Michał Parniak},

doi = {10.1038/s41467-022-28066-5},

issn = {2041-1723},

year  = {2022},

date = {2022-12-00},

urldate = {2022-12-00},

journal = {Nat Commun},

volume = {13},

number = {691},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:p>Existing super-resolution methods of optical imaging hold a solid place as an application in natural sciences, but many new developments allow for beating the diffraction limit in a more subtle way. One of the recently explored strategies to fully exploit information already present in the field is to perform a quantum-inspired tailored measurements. Here we exploit the full spectral information of the optical field in order to beat the Rayleigh limit in spectroscopy. We employ an optical quantum memory with spin-wave storage and an embedded processing capability to implement a time-inversion interferometer for input light, projecting the optical field in the symmetric-antisymmetric mode basis. Our tailored measurement achieves a resolution of 15 kHz and requires 20 times less photons than a corresponding Rayleigh-limited conventional method. We demonstrate the advantage of our technique over both conventional spectroscopy and heterodyne measurements, showing potential for application in distinguishing ultra-narrowband emitters, optical communication channels, or signals transduced from lower-frequency domains.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Clark2022,

title = {Exploiting non-linear effects in optomechanical sensors with continuous photon-counting},

author = {Lewis A. Clark and Bartosz Markowicz and Jan Kołodyński},

doi = {10.22331/q-2022-09-20-812},

issn = {2521-327X},

year  = {2022},

date = {2022-09-20},

urldate = {2022-09-20},

journal = {Quantum},

volume = {6},

number = {812},

publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},

abstract = {<jats:p>Optomechanical systems are rapidly becoming one of the most promising platforms for observing quantum behaviour, especially at the macroscopic level. Moreover, thanks to their state-of-the-art methods of fabrication, they may now enter regimes of non-linear interactions between their constituent mechanical and optical degrees of freedom. In this work, we show how this novel opportunity may serve to construct a new generation of optomechanical sensors. We consider the canonical optomechanical setup with the detection scheme being based on time-resolved counting of photons leaking from the cavity. By performing simulations and resorting to Bayesian inference, we demonstrate that the non-classical correlations of the detected photons may crucially enhance the sensor performance in real time. We believe that our work may stimulate a new direction in the design of such devices, while our methods apply also to other platforms exploiting non-linear light-matter interactions and photon detection.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bagchi2022,

title = {Inferred-variance uncertainty relations in the presence of quantum entanglement},

author = {Shrobona Bagchi and Chandan Datta and Pankaj Agrawal},

doi = {10.1103/physreva.106.022203},

issn = {2469-9934},

year  = {2022},

date = {2022-08-00},

journal = {Phys. Rev. A},

volume = {106},

number = {2},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fabre2022,

title = {Spectral single photons characterization using generalized Hong–Ou–Mandel interferometry},

author = {Nicolas Fabre},

doi = {10.1080/09500340.2022.2073613},

issn = {1362-3044},

year  = {2022},

date = {2022-07-12},

journal = {Journal of Modern Optics},

volume = {69},

number = {12},

pages = {653--664},

publisher = {Informa UK Limited},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Takahashi2022,

title = {Creating and destroying coherence with quantum channels},

author = {Masaya Takahashi and Swapan Rana and Alexander Streltsov},

doi = {10.1103/physreva.105.l060401},

issn = {2469-9934},

year  = {2022},

date = {2022-06-00},

urldate = {2022-06-00},

journal = {Phys. Rev. A},

volume = {105},

number = {L060401},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Albarelli2022,

title = {Quantum Asymmetry and Noisy Multimode Interferometry},

author = {Francesco Albarelli and Mateusz Mazelanik and Michał Lipka and Alexander Streltsov and Michał Parniak and Rafał Demkowicz-Dobrzański},

doi = {10.1103/physrevlett.128.240504},

issn = {1079-7114},

year  = {2022},

date = {2022-06-00},

urldate = {2022-06-00},

journal = {Phys. Rev. Lett.},

volume = {128},

number = {240504},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Miller2022,

title = {Optimally preserving quantum correlations and coherence with eternally non-Markovian dynamics},

author = {Marek Miller and Kang-Da Wu and Manfredi Scalici and Jan Kołodyński and Guo-Yong Xiang and Chuan-Feng Li and Guang-Can Guo and Alexander Streltsov},

doi = {10.1088/1367-2630/ac6820},

issn = {1367-2630},

year  = {2022},

date = {2022-05-01},

urldate = {2022-05-01},

journal = {New J. Phys.},

volume = {24},

number = {053022},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>We demonstrate, both analytically and experimentally, the usefulness of non-Markovianity for preserving correlations and coherence in quantum systems. For this, we consider a broad class of qubit evolutions, having a decoherence matrix separated from zero for large times. While any such Markovian evolution leads to an exponential loss of correlations, non-Markovianity can help to preserve correlations even in the limit <jats:italic>t</jats:italic> → ∞. In fact, under general assumptions, eternally non-Markovian evolution naturally emerges as the one that allows for optimal preservation of quantum correlations. For covariant qubit evolutions, we also show that non-Markovianity can be used to preserve quantum coherence at all times, which is an important resource for quantum metrology. We explicitly demonstrate this effect experimentally with linear optics, by implementing the optimal non-Markovian quantum evolution.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fabre2022b,

title = {Interferometric signature of different spectral symmetries of biphoton states},

author = {N. Fabre},

doi = {10.1103/physreva.105.053716},

issn = {2469-9934},

year  = {2022},

date = {2022-05-00},

urldate = {2022-05-00},

journal = {Phys. Rev. A},

volume = {105},

number = {053716},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kurdzialek2022,

title = {Back to sources – the role of losses and coherence in super-resolution imaging revisited},

author = {Stanislaw Kurdzialek},

doi = {10.22331/q-2022-04-27-697},

issn = {2521-327X},

year  = {2022},

date = {2022-04-27},

urldate = {2022-04-27},

journal = {Quantum},

volume = {6},

number = {697},

publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},

abstract = {<jats:p>Photon losses are intrinsic for any translationally invariant optical imaging system with a non-trivial Point Spread Function, and the relation between the transmission factor and the coherence properties of an imaged object is universal – we demonstrate the rigorous proof of this statement, based on the principles of quantum mechanics. The fundamental limit on the precision of estimating separation between two partially coherent sources is then derived. The careful study of the role of photon losses allows to resolve conflicting claims present in previous works. We compute the Quantum Fisher Information for the generic model of optical 4f imaging system, and use prior considerations to validate the result for a general, translationally invariant imaging apparatus. We prove that the spatial-mode demultiplexing (SPADE) measurement, optimal for non-coherent sources, remains optimal for an arbitrary degree of coherence. Moreover, we show that some approximations, omnipresent in theoretical works about optical imaging, inevitably lead to unphysical, zero-transmission models, resulting in misleading claims regarding fundamental resolution limits.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jørgensen2022,

title = {Bayesian quantum thermometry based on thermodynamic length},

author = {Mathias R. Jørgensen and Jan Kołodyński and Mohammad Mehboudi and Martí Perarnau-Llobet and Jonatan B. Brask},

doi = {10.1103/physreva.105.042601},

issn = {2469-9934},

year  = {2022},

date = {2022-04-00},

urldate = {2022-04-00},

journal = {Phys. Rev. A},

volume = {105},

number = {042601},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mehboudi2022,

title = {Fundamental Limits in Bayesian Thermometry and Attainability via Adaptive Strategies},

author = {Mohammad Mehboudi and Mathias R. Jørgensen and Stella Seah and Jonatan B. Brask and Jan Kołodyński and Martí Perarnau-Llobet},

doi = {10.1103/physrevlett.128.130502},

issn = {1079-7114},

year  = {2022},

date = {2022-04-00},

urldate = {2022-04-00},

journal = {Phys. Rev. Lett.},

volume = {128},

number = {130502},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Len2022b,

title = {Multiparameter estimation for qubit states with collective measurements: a case study},

author = {Yink Loong Len},

doi = {10.1088/1367-2630/ac599d},

issn = {1367-2630},

year  = {2022},

date = {2022-03-01},

urldate = {2022-03-01},

journal = {New J. Phys.},

volume = {24},

number = {033037},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>Quantum estimation involving multiple parameters remains an important problem of both theoretical and practical interest. In this work, we study the problem of simultaneous estimation of two parameters that are respectively associate with the length and direction of the Bloch vector for identically prepared qubit states that is confined to a plane, where in order to obtain the optimal estimation precision for both parameters, collective measurements on multiple qubits are necessary. Upon treating <jats:italic>N</jats:italic> qubits as an ensemble of spin-1/2 systems, we show that simultaneous optimal estimation for both parameters can be attained asymptotically with a simple collective measurement strategy—first, we estimate the length parameter by measuring the populations in spaces corresponding to different total angular momentum values <jats:italic>j</jats:italic>, then we estimate the direction parameter by performing a spin projection onto an optimal basis. Furthermore, we show that when the state is nearly pure, for sufficiently but not arbitrarily large <jats:italic>N</jats:italic>, most information will be captured in the largest three <jats:italic>j</jats:italic>-subspaces. Then, we study how the total angular-momentum measurement can be realized by observing output signatures from a Bell multiport setup, either exactly for <jats:italic>N</jats:italic> = 2, 3, or approximately when the qubits are nearly pure for other <jats:italic>N</jats:italic> values. We also obtain numerical results that suggest that using a Bell multiport setup, one can distinguish between projection onto the <jats:italic>j</jats:italic> = <jats:italic>N</jats:italic>/2 and <jats:italic>j</jats:italic> = <jats:italic>N</jats:italic>/2 − 1 subspaces from their respective interference signatures at the output.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kurzyna2022,

title = {Variable electro-optic shearing interferometry for ultrafast single-photon-level pulse characterization},

author = {Stanisław Kurzyna and Marcin Jastrzębski and Nicolas Fabre and Wojciech Wasilewski and Michał Lipka and Michał Parniak},

doi = {10.1364/oe.471108},

issn = {1094-4087},

year  = {2022},

date = {2022-00-00},

urldate = {2022-00-00},

journal = {Opt. Express},

volume = {30},

number = {22},

pages = {39826-39839},

publisher = {Optica Publishing Group},

abstract = {<jats:p>Despite the multitude of available methods, the characterization of ultrafast pulses remains a challenging endeavor, especially at the single-photon level. We introduce a pulse characterization scheme that maps the magnitude of its short-time Fourier transform. Contrary to many well-known solutions it does not require nonlinear effects and is therefore suitable for single-photon-level measurements. Our method is based on introducing a series of controlled time and frequency shifts, where the latter is performed via an electro-optic modulator allowing a fully-electronic experimental control. We characterized the full spectral and temporal width of a classical and single-photon-level pulse and successfully tested the applicability of the reconstruction algorithm of the spectral phase and amplitude. The method can be extended by implementing a phase-sensitive measurement and is naturally well-suited to partially-incoherent light.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Borówka2022,

title = {Sensitivity of a Rydberg-atom receiver to frequency and amplitude

				modulation of microwaves},

author = {Sebastian Borówka and Uliana Pylypenko and Mateusz Mazelanik and Michał Parniak},

doi = {10.1364/ao.472295},

issn = {2155-3165},

year  = {2022},

date = {2022-00-00},

journal = {Appl. Opt.},

volume = {61},

number = {29},

publisher = {Optica Publishing Group},

abstract = {Electromagnetically induced transparency in atomic systems involving Rydberg states

					is known to be a sensitive probe of incident microwave (MW) fields, in

					particular those resonant with Rydberg-to-Rydberg transitions. Here we

					propose an intelligible analytical model of a Rydberg atomic

					receiver’s response to amplitude- (AM) and frequency-modulated (FM)

					signals and compare it with experimental results, presenting a setup

					that allows sending signals with either AM or FM and evaluating their

					efficiency with demodulation. Additionally, the setup reveals a

					detection configuration using all circular polarizations for optical

					fields and allowing detection of a circularly polarized MW field,

					propagating colinearly with optical beams. In our measurements, we

					systematically show that several parameters exhibit local optimum

					characteristics and then estimate these optimal parameters and working

					ranges, addressing the need to devise a robust Rydberg MW sensor and

					its operational protocol.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Amorós-Binefa2021,

title = {Noisy atomic magnetometry in real time},

author = {Júlia Amorós-Binefa and Jan Kołodyński},

doi = {10.1088/1367-2630/ac3b71},

issn = {1367-2630},

year  = {2021},

date = {2021-12-01},

urldate = {2021-12-01},

journal = {New J. Phys.},

volume = {23},

number = {123030},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>Continuously monitored atomic spin-ensembles allow, in principle, for real-time sensing of external magnetic fields beyond classical limits. Within the linear-Gaussian regime, thanks to the phenomenon of measurement-induced spin-squeezing, they attain a quantum-enhanced scaling of sensitivity both as a function of time, <jats:italic>t</jats:italic>, and the number of atoms involved, <jats:italic>N</jats:italic>. In our work, we rigorously study how such conclusions based on Kalman filtering methods change when inevitable imperfections are taken into account: in the form of collective noise, as well as stochastic fluctuations of the field in time. We prove that even an infinitesimal amount of noise disallows the error to be arbitrarily diminished by simply increasing <jats:italic>N</jats:italic>, and forces it to eventually follow a classical-like behaviour in <jats:italic>t</jats:italic>. However, we also demonstrate that, ‘thanks’ to the presence of noise, in most regimes the model based on a homodyne-like continuous measurement actually achieves the ultimate sensitivity allowed by the decoherence, yielding then the optimal quantum-enhancement. We are able to do so by constructing a noise-induced lower bound on the error that stems from a general method of classically simulating a noisy quantum evolution, during which the stochastic parameter to be estimated—here, the magnetic field—is encoded. The method naturally extends to schemes beyond the linear-Gaussian regime, in particular, also to ones involving feedback or active control.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2021d,

title = {Massively-multiplexed generation of Bell-type entanglement using a quantum memory},

author = {Michał Lipka and Mateusz Mazelanik and Adam Leszczyński and Wojciech Wasilewski and Michał Parniak},

doi = {10.1038/s42005-021-00551-1},

issn = {2399-3650},

year  = {2021},

date = {2021-12-00},

urldate = {2021-12-00},

journal = {Commun Phys},

volume = {4},

number = {46},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:title>Abstract</jats:title><jats:p>High-rate generation of hybrid photon-matter entanglement remains a fundamental building block of quantum network architectures enabling protocols such as quantum secure communication or quantum distributed computing. While a tremendous effort has been made to overcome technological constraints limiting the efficiency and coherence times of current systems, an important complementary approach is to employ parallel and multiplexed architectures. Here we follow this approach experimentally demonstrating the generation of bipartite polarization-entangled photonic states across more than 500 modes, with a programmable delay for the second photon enabled by qubit storage in a wavevector-multiplexed cold-atomic quantum memory. We demonstrate Clauser, Horne, Shimony, Holt inequality violation by over 3 standard deviations, lasting for at least 45 <jats:italic>μ</jats:italic>s storage time for half of the modes. The ability to shape hybrid entanglement between the polarization and wavevector degrees of freedom provides not only multiplexing capabilities but also brings prospects for novel protocols.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Naikoo2021b,

title = {Projective measurements under qubit quantum channels},

author = {Javid Naikoo and Subhashish Banerjee and A. K. Pan and Sibasish Ghosh},

doi = {10.1103/physreva.104.042608},

issn = {2469-9934},

year  = {2021},

date = {2021-10-00},

urldate = {2021-10-00},

journal = {Phys. Rev. A},

volume = {104},

number = {042608},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2021,

title = {Single-Photon Hologram of a Zero-Area Pulse},

author = {Michał Lipka and Michał Parniak},

doi = {10.1103/physrevlett.127.163601},

issn = {1079-7114},

year  = {2021},

date = {2021-10-00},

urldate = {2021-10-00},

journal = {Phys. Rev. Lett.},

volume = {127},

number = {163601},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kondra2021,

title = {Catalytic Transformations of Pure Entangled States},

author = {Tulja Varun Kondra and Chandan Datta and Alexander Streltsov},

doi = {10.1103/physrevlett.127.150503},

issn = {1079-7114},

year  = {2021},

date = {2021-10-00},

urldate = {2021-10-00},

journal = {Phys. Rev. Lett.},

volume = {127},

number = {150503},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Francesconi2021,

title = {Anyonic Two-Photon Statistics with a Semiconductor Chip},

author = {Saverio Francesconi and Arnault Raymond and Nicolas Fabre and Aristide Lemaître and Maria I. Amanti and Perola Milman and Florent Baboux and Sara Ducci},

doi = {10.1021/acsphotonics.1c00901},

issn = {2330-4022},

year  = {2021},

date = {2021-09-15},

journal = {ACS Photonics},

volume = {8},

number = {9},

pages = {2764--2769},

publisher = {American Chemical Society (ACS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2021,

title = {Experimental Progress on Quantum Coherence: Detection, Quantification, and Manipulation},

author = {Kang‐Da Wu and Alexander Streltsov and Bartosz Regula and Guo‐Yong Xiang and Chuan‐Feng Li and Guang‐Can Guo},

doi = {10.1002/qute.202100040},

issn = {2511-9044},

year  = {2021},

date = {2021-09-00},

urldate = {2021-09-00},

journal = {Adv Quantum Tech},

volume = {4},

number = {2100040},

publisher = {Wiley},

abstract = {<jats:title>Abstract</jats:title><jats:p>Quantum coherence is a fundamental property of quantum systems, separating quantum from classical physics. Recently, there has been significant interest in the characterization of quantum coherence as a resource, investigating how coherence can be extracted and used for quantum technological applications. In this work, the progress of this research is reviewed, focusing in particular on recent experimental efforts. After a brief review of the underlying theory, the main platforms for realizing the experiments are discussed: linear optics, nuclear magnetic resonance, and superconducting systems. Experimental detection and quantification of coherence, experimental state conversion and coherence distillation, and experiments investigating the dynamics of quantum coherence are then considered. Experiments exploring the connections between coherence and uncertainty relations, path information, and coherence of operations and measurements are also reviewed. Experimental efforts on multipartite and multilevel coherence are also discussed.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lukanowski2021,

title = {Capacity of a Lossy Photon Channel With Direct Detection},

author = {Karol Lukanowski and Marcin Jarzyna},

doi = {10.1109/tcomm.2021.3075714},

issn = {1558-0857},

year  = {2021},

date = {2021-08-00},

journal = {IEEE Trans. Commun.},

volume = {69},

number = {8},

pages = {5059--5068},

publisher = {Institute of Electrical and Electronics Engineers (IEEE)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jarzyna2021,

title = {Attaining classical capacity per unit cost of noisy bosonic Gaussian channels},

author = {Marcin Jarzyna},

doi = {10.1103/physreva.104.022605},

issn = {2469-9934},

year  = {2021},

date = {2021-08-00},

urldate = {2021-08-00},

journal = {Phys. Rev. A},

volume = {104},

number = {022605},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fabre2021,

title = {Parameter estimation of time and frequency shifts with generalized Hong-Ou-Mandel interferometry},

author = {N. Fabre and S. Felicetti},

doi = {10.1103/physreva.104.022208},

issn = {2469-9934},

year  = {2021},

date = {2021-08-00},

urldate = {2021-08-00},

journal = {Phys. Rev. A},

volume = {104},

number = {022208},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Naikoo2021,

title = {PT	    	   symmetric evolution, coherence and violation of Leggett–Garg inequalities},

author = {Javid Naikoo and Swati Kumari and Subhashish Banerjee and A K Pan},

doi = {10.1088/1751-8121/ac0546},

issn = {1751-8121},

year  = {2021},

date = {2021-07-09},

urldate = {2021-07-09},

journal = {J. Phys. A: Math. Theor.},

volume = {54},

number = {275303},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mazelanik2021,

title = {Real-time ghost imaging of Bell-nonlocal entanglement between a photon and a quantum memory},

author = {Mateusz Mazelanik and Adam Leszczyński and Michał Lipka and Wojciech Wasilewski and Michał Parniak},

doi = {10.22331/q-2021-07-01-493},

issn = {2521-327X},

year  = {2021},

date = {2021-07-01},

urldate = {2021-07-01},

journal = {Quantum},

volume = {5},

number = {493},

publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},

abstract = {<jats:p>Certification of nonlocality of quantum mechanics is an important fundamental test that typically requires prolonged data collection and is only revealed in an in-depth analysis. These features are often particularly exposed in hybrid systems, such as interfaces between light and atomic ensembles. Certification of entanglement from images acquired with single-photon camera can mitigate this issue by exploiting multiplexed photon generation. Here we demonstrate this feature in a quantum memory (QM) operating in a real-time feedback mode. Through spatially-multimode spin-wave storage the QM enables operation of the real-time ghost imaging (GI) protocol. By properly preparing the spatial phase of light emitted by the atoms we enable observation of Bell-type nonlocality from a single image acquired in the far field as witnessed by the Bell parameter of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>S</mml:mi><mml:mo>=</mml:mo><mml:mn>2.227</mml:mn><mml:mo>±</mml:mo><mml:mn>0.007</mml:mn><mml:mo>></mml:mo><mml:mn>2</mml:mn></mml:math>. Our results are an important step towards fast and efficient utilization of multimode quantum memories both in protocols and in fundamental tests.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Barratt2021,

title = {Asymmetric arms maximize visibility in hot-electron interferometers},

author = {Clarissa J. Barratt and Sungguen Ryu and Lewis A. Clark and H.-S. Sim and Masaya Kataoka and Clive Emary},

doi = {10.1103/physrevb.104.035436},

issn = {2469-9969},

year  = {2021},

date = {2021-07-00},

urldate = {2021-07-00},

journal = {Phys. Rev. B},

volume = {104},

number = {035436},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Farkas2021,

title = {Bell Nonlocality Is Not Sufficient for the Security of Standard Device-Independent Quantum Key Distribution Protocols},

author = {Máté Farkas and Maria Balanzó-Juandó and Karol Łukanowski and Jan Kołodyński and Antonio Acín},

doi = {10.1103/physrevlett.127.050503},

issn = {1079-7114},

year  = {2021},

date = {2021-07-00},

urldate = {2021-07-00},

journal = {Phys. Rev. Lett.},

volume = {127},

number = {050503},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2021c,

title = {Entanglement distribution with wavevector-multiplexed quantum memory},

author = {Michał Lipka and Mateusz Mazelanik and Michał Parniak},

doi = {10.1088/1367-2630/abf79a},

issn = {1367-2630},

year  = {2021},

date = {2021-05-01},

urldate = {2021-05-01},

journal = {New J. Phys.},

volume = {23},

number = {053012},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>Feasible distribution of quantum entanglement over long distances remains a fundamental step towards quantum secure communication and quantum network implementations. Quantum repeater nodes based on quantum memories promise to overcome exponential signal decay inherent to optical implementations of quantum communication. While performance of current quantum memories hinders their practical application, multimode solutions with multiplexing can offer tremendous increase in entanglement distribution rates. We propose to use a wavevector-multiplexed atomic quantum memory (WV-MUX-QM) as a fundamental block of a multiplexed quantum repeater architecture. We show the WV-MUX-QM platform to provide quasi-deterministic entanglement generation over extended distances, mitigating the fundamental issue of optical loss even with currently available quantum memory devices, and exceeding performance of repeaterless solutions as well as other repeater-based protocols such as temporal multiplexing. We establish the entangled-bit (ebit) rate per number of employed nodes as a practical figure of merit reflecting the cost-efficiency of larger inter-node distances.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Datta2021b,

title = {Perfect discrimination of quantum measurements using entangled systems},

author = {Chandan Datta and Tanmoy Biswas and Debashis Saha and Remigiusz Augusiak},

doi = {10.1088/1367-2630/abecaf},

issn = {1367-2630},

year  = {2021},

date = {2021-04-01},

urldate = {2021-04-01},

journal = {New J. Phys.},

volume = {23},

number = {043021},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>Distinguishing physical processes is one of the fundamental problems in quantum physics. Although distinguishability of quantum preparations and quantum channels have been studied considerably, distinguishability of quantum measurements remains largely unexplored. We investigate the problem of single-shot discrimination of quantum measurements using two strategies, one based on single quantum systems and the other one based on entangled quantum systems. First, we formally define both scenarios. We then construct sets of measurements (including non-projective) in arbitrary finite dimensions that are perfectly distinguishable within the second scenario using quantum entanglement, while not in the one based on single quantum systems. Furthermore, we show that any advantage in measurement discrimination tasks over single systems is a demonstration of Einstein–Podolsky–Rosen ‘quantum steering’. Alongside, we prove that all pure two-qubit entangled states provide an advantage in a measurement discrimination task over one-qubit systems.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2021b,

title = {Resource theory of imaginarity: Quantification and state conversion},

author = {Kang-Da Wu and Tulja Varun Kondra and Swapan Rana and Carlo Maria Scandolo and Guo-Yong Xiang and Chuan-Feng Li and Guang-Can Guo and Alexander Streltsov},

doi = {10.1103/physreva.103.032401},

issn = {2469-9934},

year  = {2021},

date = {2021-03-00},

urldate = {2021-03-00},

journal = {Phys. Rev. A},

volume = {103},

number = {032401},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2021c,

title = {Operational Resource Theory of Imaginarity},

author = {Kang-Da Wu and Tulja Varun Kondra and Swapan Rana and Carlo Maria Scandolo and Guo-Yong Xiang and Chuan-Feng Li and Guang-Can Guo and Alexander Streltsov},

doi = {10.1103/physrevlett.126.090401},

issn = {1079-7114},

year  = {2021},

date = {2021-03-00},

urldate = {2021-03-00},

journal = {Phys. Rev. Lett.},

volume = {126},

number = {090401},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{deAlmeida2021,

title = {Discrimination and estimation of incoherent sources under misalignment},

author = {J. O. de Almeida and J. Kołodyński and C. Hirche and M. Lewenstein and M. Skotiniotis},

doi = {10.1103/physreva.103.022406},

issn = {2469-9934},

year  = {2021},

date = {2021-02-00},

urldate = {2021-02-00},

journal = {Phys. Rev. A},

volume = {103},

number = {022406},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Banaszek2021,

title = {Optimization of intensity-modulation/direct-detection optical key distribution under passive eavesdropping},

author = {Konrad Banaszek and Michał Jachura and Piotr Kolenderski and Mikołaj Lasota},

doi = {10.1364/oe.444340},

issn = {1094-4087},

year  = {2021},

date = {2021-00-00},

urldate = {2021-00-00},

journal = {Opt. Express},

volume = {29},

number = {26},

pages = {43091-43103},

publisher = {Optica Publishing Group},

abstract = {<jats:p>We analyze the theoretically optimal operation of an optical key distribution (OKD) link based on fine intensity modulation of an optical signal transmitted over an attenuating channel to a direct detection receiver. With suitable digital postprocessing, the users may generate a secret key that will be unknown to an unauthorized party collecting passively a fraction of the signal that escapes detection by the legitimate recipient. The security is ensured by the presence of the shot noise that inevitably accompanies an eavesdropper’s attempt to detect the collected signal. It is shown that the key amount depends on a ratio that compares the legitimate recipient’s and eavesdropper’s capabilities to detect the signal, including noise contributed by their respective detectors. A simple proportionality relation is derived in the strong eavesdropping regime, and closed expressions for the optimal depth of binary intensity modulation as well as the discrimination thresholds for hard-decoded direct detection are given. The presented results substantially simplify the design of practical OKD systems operating under changing external conditions, e.g. variable atmospheric absorption in the case of free-space optical links.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Datta2021,

title = {Sub-Rayleigh characterization of a binary source by spatially demultiplexed coherent detection},

author = {Chandan Datta and Yink Loong Len and Karol Łukanowski and Konrad Banaszek and Marcin Jarzyna},

doi = {10.1364/oe.433990},

issn = {1094-4087},

year  = {2021},

date = {2021-00-00},

urldate = {2021-00-00},

journal = {Opt. Express},

volume = {29},

number = {22},

pages = {35592-35601},

publisher = {Optica Publishing Group},

abstract = {<jats:p>We investigate theoretically coherent detection implemented simultaneously on a set of mutually orthogonal spatial modes in the image plane as a method to characterize properties of a composite thermal source below the Rayleigh limit. A general relation between the intensity distribution in the source plane and the covariance matrix for the complex field amplitudes measured in the image plane is derived. An algorithm to estimate parameters of a two-dimensional symmetric binary source is devised and verified using Monte Carlo simulations to provide super-resolving capability for a high ratio of signal to detection noise (SNR). Specifically, the separation between two point sources can be meaningfully determined down to SNR<jats:sup>−1/2</jats:sup> in the length unit determined by the spatial spread of the transfer function of the imaging system. The presented algorithm is shown to make a nearly optimal use of the measured data in the sub-Rayleigh region.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Thomas2021,

title = {Calibration of spin-light coupling by coherently induced Faraday rotation},

author = {Rodrigo A. Thomas and Christoffer Østfeldt and Christian Bærentsen and Michał Parniak and Eugene S. Polzik},

doi = {10.1364/oe.425613},

issn = {1094-4087},

year  = {2021},

date = {2021-00-00},

urldate = {2021-00-00},

journal = {Opt. Express},

volume = {29},

number = {15},

pages = {23637-23653},

publisher = {Optica Publishing Group},

abstract = {<jats:p>Calibrating the strength of the light-matter interaction is an important experimental task in quantum information and quantum state engineering protocols. The strength of the off-resonant light-matter interaction in multi-atom spin oscillators can be characterized by the readout rate Γ<jats:sub>S</jats:sub>. Here we introduce the method named Coherently Induced FAraday Rotation (CIFAR) for determining the readout rate. The method is suited for both continuous and pulsed readout of the spin oscillator, relying only on applying a known polarization modulation to the probe laser beam and detecting a known optical polarization component. Importantly, the method does not require changes to the optical and magnetic fields performing the state preparation and probing. The CIFAR signal is also independent of the probe beam photo-detection quantum efficiency, and allows direct extraction of other parameters of the interaction, such as the tensor coupling <jats:italic>ζ</jats:italic><jats:sub>S</jats:sub>, and the damping rate <jats:italic>γ</jats:italic><jats:sub>S</jats:sub>. We verify this method in the continuous wave regime, probing a strongly coupled spin oscillator prepared in a warm cesium atomic vapour.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2021b,

title = {Fast imaging of multimode transverse–spectral correlations for twin photons},

author = {Michał Lipka and Michał Parniak},

doi = {10.1364/ol.417658},

issn = {1539-4794},

year  = {2021},

date = {2021-00-00},

urldate = {2021-00-00},

journal = {Opt. Lett.},

volume = {46},

number = {13},

pages = {3009-3012},

publisher = {Optica Publishing Group},

abstract = {<jats:p>Hyperentangled photonic states—exhibiting nonclassical correlations in

					several degrees of freedom—offer improved performance of quantum

					optical communication and computation schemes. Experimentally, a

					hyperentanglement of transverse-wave-vector and spectral modes can be

					obtained in a straightforward way with multimode parametric

					single-photon sources. Nevertheless, experimental characterization of

					such states remains challenging. Not only single-photon detection with

					high spatial resolution—a single-photon camera—is required, but also a

					suitable mode converter to observe the spectral–temporal degree of

					freedom. We experimentally demonstrate a measurement of full

					four-dimensional transverse-wave-vector–spectral correlations between

					pairs of photons produced in noncollinear spontaneous parametric

					downconversion. Utilization of a custom ultrafast single-photon camera

					provides high resolution and a short measurement time.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Parniak2021,

title = {High-frequency broadband laser phase noise cancellation using a delay line},

author = {Michał Parniak and Ivan Galinskiy and Timo Zwettler and Eugene S. Polzik},

doi = {10.1364/oe.415942},

issn = {1094-4087},

year  = {2021},

date = {2021-00-00},

urldate = {2021-00-00},

journal = {Opt. Express},

volume = {29},

number = {5},

pages = {6935-6946},

publisher = {Optica Publishing Group},

abstract = {<jats:p>Laser phase noise remains a limiting factor in many experimental settings, including metrology, time-keeping, as well as quantum optics. Hitherto this issue was addressed at low frequencies ranging from well below 1 Hz to maximally 100 kHz. However, a wide range of experiments, such as, e.g., those involving nanomechanical membrane resonators, are highly sensitive to noise at higher frequencies in the range of 100 kHz to 10 MHz, such as nanomechanical membrane resonators. Here we employ a fiber-loop delay line interferometer optimized to cancel laser phase noise at frequencies around 1.5 MHz. We achieve noise reduction in 300 kHz-wide bands with a peak reduction of more than 10 dB at desired frequencies, reaching phase noise of less than −160 dB(rad<jats:sup>2</jats:sup>/Hz) with a Ti:Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> laser. These results provide a convenient noise reduction technique to achieve deep ground-state cooling of mechanical motion.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Datta2020,

title = {Sub-Rayleigh resolution of two incoherent sources by array homodyning},

author = {Chandan Datta and Marcin Jarzyna and Yink Loong Len and Karol Łukanowski and Jan Kołodyński and Konrad Banaszek},

doi = {10.1103/physreva.102.063526},

issn = {2469-9934},

year  = {2020},

date = {2020-12-00},

urldate = {2020-12-00},

journal = {Phys. Rev. A},

volume = {102},

number = {063526},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yuan2020,

title = {Direct estimation of quantum coherence by collective measurements},

author = {Yuan Yuan and Zhibo Hou and Jun-Feng Tang and Alexander Streltsov and Guo-Yong Xiang and Chuan-Feng Li and Guang-Can Guo},

doi = {10.1038/s41534-020-0280-6},

issn = {2056-6387},

year  = {2020},

date = {2020-12-00},

urldate = {2020-12-00},

journal = {npj Quantum Inf},

volume = {6},

number = {46},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:title>Abstract</jats:title><jats:p>The recently established resource theory of quantum coherence allows for a quantitative understanding of the superposition principle, with applications reaching from quantum computing to quantum biology. While different quantifiers of coherence have been proposed in the literature, their efficient estimation in today’s experiments remains a challenge. Here, we introduce a collective measurement scheme for estimating the amount of coherence in quantum states, which requires entangled measurements on two copies of the state. As we show by numerical simulations, our scheme outperforms other estimation methods based on tomography or adaptive measurements, leading to a higher precision in a large parameter range for estimating established coherence quantifiers of qubit and qutrit states. We show that our method is accessible with today’s technology by implementing it experimentally with photons, finding a good agreement between experiment and theory.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2020,

title = {Quantum coherence and state conversion: theory and experiment},

author = {Kang-Da Wu and Thomas Theurer and Guo-Yong Xiang and Chuan-Feng Li and Guang-Can Guo and Martin B. Plenio and Alexander Streltsov},

doi = {10.1038/s41534-020-0250-z},

issn = {2056-6387},

year  = {2020},

date = {2020-12-00},

urldate = {2020-12-00},

journal = {npj Quantum Inf},

volume = {6},

number = {22},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:title>Abstract</jats:title><jats:p>The resource theory of coherence studies the operational value of superpositions in quantum technologies. A key question in this theory concerns the efficiency of manipulation and interconversion of the resource. Here, we solve this question completely for qubit states by determining the optimal probabilities for mixed-state conversions via stochastic incoherent operations. Extending the discussion to distributed scenarios, we introduce and address the task of assisted incoherent state conversion, where the process is enhanced by making use of correlations with a second party. Building on these results, we demonstrate experimentally that the optimal state-conversion probabilities can be achieved in a linear optics setup. This paves the way towards real world applications of coherence transformations in current quantum technologies.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jarzyna2020,

title = {Geometric Approach to Quantum Statistical Inference},

author = {Marcin Jarzyna and Jan Kolodynski},

doi = {10.1109/jsait.2020.3017469},

issn = {2641-8770},

year  = {2020},

date = {2020-08-00},

journal = {IEEE J. Sel. Areas Inf. Theory},

volume = {1},

number = {2},

pages = {367--386},

publisher = {Institute of Electrical and Electronics Engineers (IEEE)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Streltsov2020,

title = {Rates of Multipartite Entanglement Transformations},

author = {A. Streltsov and C. Meignant and J. Eisert},

doi = {10.1103/physrevlett.125.080502},

issn = {1079-7114},

year  = {2020},

date = {2020-08-00},

urldate = {2020-08-00},

journal = {Phys. Rev. Lett.},

volume = {125},

number = {080502},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Banaszek2020,

title = {Quantum Limits in Optical Communications},

author = {Konrad Banaszek and Ludwig Kunz and Michal Jachura and Marcin Jarzyna},

doi = {10.1109/jlt.2020.2973890},

issn = {1558-2213},

year  = {2020},

date = {2020-05-15},

journal = {J. Lightwave Technol.},

volume = {38},

number = {10},

pages = {2741--2754},

publisher = {Institute of Electrical and Electronics Engineers (IEEE)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kołodyński2020,

title = {Device-independent quantum key distribution with single-photon sources},

author = {Jan Kołodyński and Alejandro Máttar and Paul Skrzypczyk and Erik Woodhead and Daniel Cavalcanti and Konrad Banaszek and Antonio Acín},

doi = {10.22331/q-2020-04-30-260},

issn = {2521-327X},

year  = {2020},

date = {2020-04-30},

urldate = {2020-04-30},

journal = {Quantum},

volume = {4},

number = {260},

publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},

abstract = {<jats:p><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mtext class="MJX-tex-mathit" mathvariant="italic">Device-independent quantum key distribution</mml:mtext></mml:mrow></mml:math> protocols allow two honest users to establish a secret key with minimal levels of trust on the provider, as security is proven without any assumption on the inner working of the devices used for the distribution. Unfortunately, the implementation of these protocols is challenging, as it requires the observation of a large Bell-inequality violation between the two distant users. Here, we introduce novel photonic protocols for device-independent quantum key distribution exploiting <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mtext class="MJX-tex-mathit" mathvariant="italic">single-photon sources</mml:mtext></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow class="MJX-TeXAtom-ORD"><mml:mtext class="MJX-tex-mathit" mathvariant="italic">heralding-type architectures</mml:mtext></mml:mrow></mml:math>. The heralding process is designed so that transmission losses become irrelevant for security. We then show how the use of single-photon sources for entanglement distribution in these architectures, instead of standard entangled-pair generation schemes, provides significant improvements on the attainable key rates and distances over previous proposals. Given the current progress in single-photon sources, our work opens up a promising avenue for device-independent quantum key distribution implementations.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kunz2020,

title = {Low-cost limit of classical communication with restricted quantum measurements},

author = {Ludwig Kunz and Marcin Jarzyna and Wojciech Zwoliński and Konrad Banaszek},

doi = {10.1088/1367-2630/ab7bd3},

issn = {1367-2630},

year  = {2020},

date = {2020-04-01},

urldate = {2020-04-01},

journal = {New J. Phys.},

volume = {22},

number = {043010},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>We consider a communication scenario where classical information is encoded in an ensemble of quantum states that admit a power series expansion in a cost parameter and converge to a single zero cost state with vanishing cost. For a given measurement scheme, we derive an approximate expression for mutual information in the leading order of the cost parameter. The general results are applied to selected problems in optical communication, where coherent states of light are used as input symbols and the cost is quantified as the average number of photons per symbol. We show that for an arbitrary individual measurement on phase shift keyed (PSK) symbols, the photon information efficiency is upper bounded by 2 nats of information per photon in the low-cost limit, which coincides with the conventional homodyne detection bound. The presented low-cost approximation facilitates a systematic analysis of few-symbol measurements that exhibit superadditivity of accessible information. For the binary PSK alphabet of coherent states, we present designs for two- and three-symbol measurement schemes based on linear optics, homodyning, and single photon detection that offer respectively 2.49% and 3.40% enhancement relative to individual measurements. We also show how designs for scalable superadditive measurement schemes emerge from the introduced low-cost formalism.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2020,

title = {Quantum Fingerprinting Over AWGN Channels With Power-Limited Optical Signals},

author = {Michal Lipka and Marcin Jarzyna and Konrad Banaszek},

doi = {10.1109/jsac.2020.2968996},

issn = {1558-0008},

year  = {2020},

date = {2020-03-00},

journal = {IEEE J. Select. Areas Commun.},

volume = {38},

number = {3},

pages = {496--505},

publisher = {Institute of Electrical and Electronics Engineers (IEEE)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Streltsov2020b,

title = {Quantum state merging with bound entanglement},

author = {Alexander Streltsov},

doi = {10.1088/1367-2630/ab70d7},

issn = {1367-2630},

year  = {2020},

date = {2020-02-01},

urldate = {2020-02-01},

journal = {New J. Phys.},

volume = {22},

number = {023032},

publisher = {IOP Publishing},

abstract = {<jats:title>Abstract</jats:title>

               <jats:p>Quantum state merging is one of the most important protocols in quantum information theory. In this task two parties aim to merge their parts of a pure tripartite state by making use of additional singlets while preserving correlations with a third party. We study a variation of this scenario where the shared state is not necessarily pure, and the merging parties have free access to local operations, classical communication, and positive partial transpose (PPT) entangled states. We provide general conditions for a state to admit perfect merging, and present a family of fully separable states which cannot be perfectly merged if the merging parties have no access to additional singlets. We also show that free PPT entangled states do not give any advantage for merging of pure states, and the conditional entropy plays the same role as in standard quantum state merging quantifying the rate of additional singlets needed to perfectly merge the state.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kołodyński2020b,

title = {Entanglement negativity as a universal non-Markovianity witness},

author = {Jan Kołodyński and Swapan Rana and Alexander Streltsov},

doi = {10.1103/physreva.101.020303},

issn = {2469-9934},

year  = {2020},

date = {2020-02-00},

urldate = {2020-02-00},

journal = {Phys. Rev. A},

volume = {101},

number = {020303},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Len2020,

title = {Resolution limits of spatial mode demultiplexing with noisy detection},

author = {Yink Loong Len and Chandan Datta and Michał Parniak and Konrad Banaszek},

doi = {10.1142/s0219749919410156},

issn = {1793-6918},

year  = {2020},

date = {2020-02-00},

urldate = {2020-02-00},

journal = {Int. J. Quantum Inform.},

volume = {18},

number = {1941015},

issue = {01},

publisher = {World Scientific Pub Co Pte Lt},

abstract = {<jats:p> We consider the problem of estimating the spatial separation between two mutually incoherent point light sources using the super-resolution imaging technique based on spatial mode demultiplexing (SPADE) with noisy detectors. We show that in the presence of noise, the resolution of the measurement is limited by the signal-to-noise ratio (SNR) and the minimum resolvable spatial separation has a characteristic dependence of [Formula: see text]. Several detection techniques, including direct photon counting, as well as homodyne and heterodyne detection are considered. </jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Raymer2020,

title = {Time-frequency optical filtering: efficiency vs. temporal-mode discrimination in incoherent and coherent implementations},

author = {Michael G. Raymer and Konrad Banaszek},

doi = {10.1364/oe.405618},

issn = {1094-4087},

year  = {2020},

date = {2020-00-00},

urldate = {2020-00-00},

journal = {Opt. Express},

volume = {28},

number = {22},

pages = {32819-32836},

publisher = {Optica Publishing Group},

abstract = {<jats:p>Time-frequency (TF) filtering of analog signals has played a crucial role in the development of radio-frequency communications and is currently being recognized as an essential capability for communications, both classical and quantum, in the optical frequency domain. How best to design optical time-frequency (TF) filters to pass a targeted temporal mode (TM), and to reject background (noise) photons in the TF detection window? The solution for ‘coherent’ TF filtering is known—the quantum pulse gate—whereas the conventional, more common method is implemented by a sequence of incoherent spectral filtering and temporal gating operations. To compare these two methods, we derive a general formalism for two-stage incoherent time-frequency filtering, finding expressions for signal pulse transmission efficiency, and for the ability to discriminate TMs, which allows the blocking of unwanted background light. We derive the tradeoff between efficiency and TM discrimination ability, and find a remarkably concise relation between these two quantities and the time-bandwidth product of the combined filters. We apply the formalism to two examples—rectangular filters or Gaussian filters—both of which have known orthogonal-function decompositions. The formalism can be applied to any state of light occupying the input temporal mode, e.g., ‘classical’ coherent-state signals or pulsed single-photon states of light. In contrast to the radio-frequency domain, where coherent detection is standard and one can use coherent matched filtering to reject noise, in the optical domain direct detection is optimal in a number of scenarios where the signal flux is extremely small. Our analysis shows how the insertion loss and SNR change when one uses incoherent optical filters to reject background noise, followed by direct detection, e.g. photon counting. We point out implications in classical and quantum optical communications. As an example, we study quantum key distribution, wherein strong rejection of background noise is necessary to maintain a high quality of entanglement, while high signal transmission is needed to ensure a useful key generation rate.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mazelanik2020,

title = {Temporal imaging for ultra-narrowband few-photon states of light},

author = {Mateusz Mazelanik and Adam Leszczyński and Michał Lipka and Michał Parniak and Wojciech Wasilewski},

doi = {10.1364/optica.382891},

issn = {2334-2536},

year  = {2020},

date = {2020-00-00},

urldate = {2020-00-00},

journal = {Optica},

volume = {7},

number = {3},

pages = {203-208},

publisher = {Optica Publishing Group},

abstract = {<jats:p>Plenty of quantum information protocols are enabled by manipulation and detection of photonic spectro-temporal degrees of freedom via light–matter interfaces. While present implementations are well suited for high-bandwidth photon sources such as quantum dots, they lack the high resolution required for intrinsically narrowband light–atom interactions. Here, we demonstrate far-field temporal imaging based on ac-Stark spatial spin-wave phase manipulation in a multimode gradient echo memory. We achieve a spectral resolution of 20 kHz with MHz-level bandwidth and an ultralow noise equivalent to 0.023 photons, enabling operation in the single-quantum regime.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DiMario2019,

title = {Optimized communication strategies with binary coherent states over phase noise channels},

author = {M. T. DiMario and L. Kunz and K. Banaszek and F. E. Becerra},

doi = {10.1038/s41534-019-0177-4},

issn = {2056-6387},

year  = {2019},

date = {2019-12-00},

urldate = {2019-12-00},

journal = {npj Quantum Inf},

volume = {5},

number = {65},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:title>Abstract</jats:title><jats:p>The achievable rate of information transfer in optical communications is determined by the physical properties of the communication channel, such as the intrinsic channel noise. Bosonic phase noise channels, a class of non-Gaussian channels, have emerged as a relevant noise model in quantum information and optical communication. However, while the fundamental limits for communication over Gaussian channels have been extensively studied, the properties of communication over Bosonic phase noise channels are not well understood. Here we propose and demonstrate experimentally the concept of optimized communication strategies for communication over phase noise channels to enhance information transfer beyond what is possible with conventional methods of modulation and detection. Two key ingredients are generalized constellations of coherent states that interpolate between standard on-off keying and binary phase-shift keying formats, and non-Gaussian measurements based on photon number resolving detection of the coherently displaced signal. For a given power constraint and channel noise strength, these novel strategies rely on joint optimization of the input alphabet and the measurement to provide enhanced communication capability over a non-Gaussian channel characterized in terms of the error rate as well as mutual information.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mazelanik2019b,

title = {Coherent spin-wave processor of stored optical pulses},

author = {Mateusz Mazelanik and Michał Parniak and Adam Leszczyński and Michał Lipka and Wojciech Wasilewski},

doi = {10.1038/s41534-019-0136-0},

issn = {2056-6387},

year  = {2019},

date = {2019-12-00},

urldate = {2019-12-00},

journal = {npj Quantum Inf},

volume = {5},

number = {22},

publisher = {Springer Science and Business Media LLC},

abstract = {<jats:title>Abstract</jats:title><jats:p>A device being a pinnacle of development of an optical quantum memory should combine the capabilities of storage, inter-communication, and processing of stored information. In particular, the ability to capture a train of optical pulses, interfere them in an arbitrary way and finally, perform on-demand release could realize arbitrary optical computation. Here we demonstrate the operation of a coherent optical memory being able to store optical pulses in the form of collective spin-wave excitations in a two-dimensional wavevector space. During storage, we perform complex beamsplitter operations and demonstrate a variety of protocols implemented at the processing stage, including real-time controlled interference of a pair of spin-wave modes with 95% visibility. The highly multimode structure of the presented memory lends itself to enhancing classical optical telecommunication, as well as parallel processing of optical qubits at the single-photon level.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mazelanik2019,

title = {Superradiant parametric conversion of spin waves},

author = {Mateusz Mazelanik and Adam Leszczyński and Michał Lipka and Wojciech Wasilewski and Michał Parniak},

doi = {10.1103/physreva.100.053850},

issn = {2469-9934},

year  = {2019},

date = {2019-11-00},

urldate = {2019-11-00},

journal = {Phys. Rev. A},

volume = {100},

number = {053850},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lipka2019,

title = {Spatial Spin-Wave Modulator for Quantum-Memory-Assisted Adaptive Measurements},

author = {Michał Lipka and Adam Leszczyński and Mateusz Mazelanik and Michał Parniak and Wojciech Wasilewski},

doi = {10.1103/physrevapplied.11.034049},

issn = {2331-7019},

year  = {2019},

date = {2019-03-00},

urldate = {2019-03-00},

journal = {Phys. Rev. Applied},

volume = {11},

number = {034049},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Parniak2019,

title = {Quantum Optics of Spin Waves through ac Stark Modulation},

author = {Michał Parniak and Mateusz Mazelanik and Adam Leszczyński and Michał Lipka and Michał Dąbrowski and Wojciech Wasilewski},

doi = {10.1103/physrevlett.122.063604},

issn = {1079-7114},

year  = {2019},

date = {2019-02-00},

urldate = {2019-02-00},

journal = {Phys. Rev. Lett.},

volume = {122},

number = {063604},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Parniak2018,

title = {Beating the Rayleigh Limit Using Two-Photon Interference},

author = {Michał Parniak and Sebastian Borówka and Kajetan Boroszko and Wojciech Wasilewski and Konrad Banaszek and Rafał Demkowicz-Dobrzański},

doi = {10.1103/physrevlett.121.250503},

issn = {1079-7114},

year  = {2018},

date = {2018-12-00},

urldate = {2018-12-00},

journal = {Phys. Rev. Lett.},

volume = {121},

number = {250503},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dąbrowski2018,

title = {Certification of high-dimensional entanglement and Einstein-Podolsky-Rosen steering with cold atomic quantum memory},

author = {Michał Dąbrowski and Mateusz Mazelanik and Michał Parniak and Adam Leszczyński and Michał Lipka and Wojciech Wasilewski},

doi = {10.1103/physreva.98.042126},

issn = {2469-9934},

year  = {2018},

date = {2018-10-00},

urldate = {2018-10-00},

journal = {Phys. Rev. A},

volume = {98},

number = {042126},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}