@article{63656,
  author       = {{Ares, Laura and Pinske, Julien and Hinrichs, Benjamin and Kolb, Martin and Sperling, Jan}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Restricted Monte Carlo wave-function method and Lindblad equation for identifying entangling open-quantum-system dynamics}}},
  doi          = {{10.1103/hcj7-8zlg}},
  volume       = {{113}},
  year         = {{2026}},
}

@article{63657,
  author       = {{Pinske, Julien and Ares, Laura and Hinrichs, Benjamin and Kolb, Martin and Sperling, Jan}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Separability Lindblad equation for dynamical open-system entanglement}}},
  doi          = {{10.1103/kd3b-bfxq}},
  volume       = {{113}},
  year         = {{2026}},
}

@unpublished{58544,
  abstract     = {{We introduce a new classification of multimode states with a fixed number of photons. This classification is based on the factorizability of homogeneous multivariate polynomials and is invariant under unitary transformations. The classes physically correspond to field excitations in terms of single and multiple photons, each of which being in an arbitrary irreducible superposition of quantized modes. We further show how the transitions between classes are rendered possible by photon addition, photon subtraction, and photon-projection nonlinearities. We explicitly put forward a design for a multilayer interferometer in which the states for different classes can be generated with state-of-the-art experimental techniques. Limitations of the proposed designs are analyzed using the introduced classification, providing a benchmark for the robustness of certain states and classes. }},
  author       = {{Kopylov, Denis and Offen, Christian and Ares, Laura and Wembe Moafo, Boris Edgar and Ober-Blöbaum, Sina and Meier, Torsten and Sharapova, Polina and Sperling, Jan}},
  title        = {{{Multiphoton, multimode state classification for nonlinear optical circuits }}},
  year         = {{2025}},
}

@article{61245,
  author       = {{Barkhausen, Franziska and Ares Santos, Laura and Schumacher, Stefan and Sperling, Jan}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{3}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Entanglement between dependent degrees of freedom: Quasiparticle correlations}}},
  doi          = {{10.1103/physreva.111.032404}},
  volume       = {{111}},
  year         = {{2025}},
}

@article{60992,
  abstract     = {{Non-Hermitian systems hosting exceptional points (EPs) exhibit enhanced sensitivity and unconventional mode dynamics. Going beyond isolated EPs, here we report on the existence of exceptional rings (ERs) in planar optical resonators with specific form of circular dichroism and TE-TM splitting. Such exceptional rings possess intriguing topologies as discussed earlier for condensed matter systems, but they remain virtually unexplored in presence of nonlinearity, for which our photonic platform is ideal. We find that when Kerr-type nonlinearity (or saturable gain) is introduced, the linear ER splits into two concentric ERs, with the larger-radius ring being a ring of third-order EPs. Transitioning from linear to nonlinear regime, we present a rigorous analysis of spectral topology and report enhanced and adjustable perturbation response in the nonlinear regime. Whereas certain features are specific to our system, the results on non-Hermitian spectral topology and nonlinearity-enhanced perturbation response are generic and equally relevant to a broad class of other nonlinear non-Hermitian systems, providing a universal framework for engineering ERs and EPs in nonlinear non-Hermitian systems.}},
  author       = {{Wingenbach, Jan and Ares Santos, Laura  and Ma, Xuekai and Sperling, Jan and Schumacher, Stefan}},
  journal      = {{Arxiv}},
  publisher    = {{Arxiv}},
  title        = {{{Sensitivity and Topology of Exceptional Rings in Nonlinear Non-Hermitian Planar Optical Microcavities}}},
  doi          = {{10.48550/ARXIV.2507.07099}},
  year         = {{2025}},
}

@article{62980,
  abstract     = {{<jats:p>We introduce a new classification of multimode states with a fixed number of photons. This classification is based on the factorizability of homogeneous multivariate polynomials and is invariant under unitary transformations. The classes physically correspond to field excitations in terms of single and multiple photons, each of which is in an arbitrary irreducible superposition of quantized modes. We further show how the transitions between classes are rendered possible by photon addition, photon subtraction, and photon-projection nonlinearities. We explicitly put forward a design for a multilayer interferometer in which the states for different classes can be generated with state-of-the-art experimental techniques. Limitations of the proposed designs are analyzed using the introduced classification, providing a benchmark for the robustness of certain states and classes.</jats:p>}},
  author       = {{Kopylov, Denis A. and Offen, Christian and Ares, Laura and Wembe Moafo, Boris Edgar and Ober-Blöbaum, Sina and Meier, Torsten and Sharapova, Polina R. and Sperling, Jan}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  number       = {{3}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Multiphoton, multimode state classification for nonlinear optical circuits}}},
  doi          = {{10.1103/sv6z-v1gk}},
  volume       = {{7}},
  year         = {{2025}},
}

@unpublished{62979,
  abstract     = {{We introduce a new classification of multimode states with a fixed number of photons. This classification is based on the factorizability of homogeneous multivariate polynomials and is invariant under unitary transformations. The classes physically correspond to field excitations in terms of single and multiple photons, each of which being in an arbitrary irreducible superposition of quantized modes. We further show how the transitions between classes are rendered possible by photon addition, photon subtraction, and photon-projection nonlinearities. We explicitly put forward a design for a multilayer interferometer in which the states for different classes can be generated with state-of-the-art experimental techniques. Limitations of the proposed designs are analyzed using the introduced classification, providing a benchmark for the robustness of certain states and classes.}},
  author       = {{Meier, Torsten and Sharapova, Polina R. and Sperling, Jan and Ober-Blöbaum, Sina and Wembe Moafo, Boris Edgar and Offen, Christian}},
  title        = {{{Multiphoton, multimode state classification for nonlinear optical circuits}}},
  year         = {{2025}},
}

@article{63021,
  abstract     = {{<jats:p>Bell measurements, entailing the projection onto one of the Bell states, play a key role in quantum information and communication, where the outcome of a variety of protocols crucially depends on the success probability of such measurements. Although in the case of qubit systems, Bell measurements can be implemented using only linear optical components, the same result is no longer true for qudits, where at least the use of ancillary photons is required. In order to circumvent this limitation, one possibility is to introduce nonlinear effects. In this work, we adopt the latter approach and propose a scalable Bell measurement scheme for high-dimensional states, exploiting multiple squeezer devices applied to a linear optical circuit for discriminating the different Bell states. Our approach does not require ancillary photons, is not limited by the dimension of the quantum states, and is experimentally scalable, thus paving the way toward the realization of an effective high-dimensional Bell measurement.</jats:p>}},
  author       = {{Bianchi, Luca and Marconi, Carlo and Sperling, Jan and Bacco, Davide}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  number       = {{2}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Predetection squeezing as a resource for high-dimensional Bell-state measurements}}},
  doi          = {{10.1103/physrevresearch.7.023038}},
  volume       = {{7}},
  year         = {{2025}},
}

@article{63534,
  abstract     = {{<jats:p>Boson sampling is a key candidate for demonstrating quantum advantage and has already yielded significant advances in quantum simulation, machine learning, and graph theory. In this work, a unification and extension of distinct forms of boson sampling is developed. The devised protocol merges discrete-variable scattershot boson sampling with continuous-variable Gaussian boson sampling. Therefore, it is rendered possible to harness the complexity of more interesting states, such as squeezed photons, in advanced sampling protocols. A generating function formalism is developed for the joint description of multiphoton and multimode light undergoing Gaussian transformations. The resulting analytical tools enable one to explore interfaces of different photonic quantum-information-processing platforms. A numerical simulation of unified sampling is carried out, benchmarking its performance, complexity, and scalability. Entanglement is characterized to exemplify the generation of quantum correlations from the nonlinear interactions of a unified sampler.</jats:p>}},
  author       = {{Bianchi, Luca and Marconi, Carlo and Ares, Laura and Bacco, Davide and Sperling, Jan}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  number       = {{4}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Unified boson sampling}}},
  doi          = {{10.1103/8hy1-m5gg}},
  volume       = {{7}},
  year         = {{2025}},
}

@article{54093,
  author       = {{Pinske, Julien and Sperling, Jan}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{5}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Unbreakable and breakable quantum censorship}}},
  doi          = {{10.1103/physreva.109.052408}},
  volume       = {{109}},
  year         = {{2024}},
}

@article{54812,
  author       = {{Weinbrenner, Lisa T. and Prasannan, Nidhin and Hansenne, Kiara and Denker, Sophia and Sperling, Jan and Brecht, Benjamin and Silberhorn, Christine and Gühne, Otfried}},
  issn         = {{0031-9007}},
  journal      = {{Physical Review Letters}},
  number       = {{24}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Certifying the Topology of Quantum Networks: Theory and Experiment}}},
  doi          = {{10.1103/physrevlett.132.240802}},
  volume       = {{132}},
  year         = {{2024}},
}

@article{55140,
  author       = {{Yasmin, Farha and Sperling, Jan}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Entanglement-assisted quantum speedup: Beating local quantum speed limits}}},
  doi          = {{10.1103/physreva.110.012424}},
  volume       = {{110}},
  year         = {{2024}},
}

@article{55173,
  author       = {{Di Fidio, Christian and Ares, Laura and Sperling, Jan}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Quantum walks and entanglement in cavity networks}}},
  doi          = {{10.1103/physreva.110.013705}},
  volume       = {{110}},
  year         = {{2024}},
}

@article{55737,
  abstract     = {{<jats:p>We report on a photonic simulator of the critical state forming at the quantum phase transition between topologically distinct Anderson insulator phases. We observe a time-staggered profile in the circular photon polarization, which originates from the interplay of a chiral and sublattice symmetry, and has recently been suggested as a signature for topological Anderson criticality within the setup. We discuss the role of statistical detuning from criticality and show that the controlled breaking of phase coherence removes the signal, revealing its origin in quantum coherence.</jats:p>
          <jats:sec>
            <jats:title/>
            <jats:supplementary-material>
              <jats:permissions>
                <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement>
                <jats:copyright-year>2024</jats:copyright-year>
              </jats:permissions>
            </jats:supplementary-material>
          </jats:sec>}},
  author       = {{Barkhofen, Sonja and De, Syamsundar and Sperling, Jan and Silberhorn, Christine and Altland, Alexander and Bagrets, Dmitry and Kim, Kun Woo and Micklitz, Tobias}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  number       = {{3}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Experimental observation of topological quantum criticality}}},
  doi          = {{10.1103/physrevresearch.6.033194}},
  volume       = {{6}},
  year         = {{2024}},
}

@article{57743,
  author       = {{Krishnaswamy, Suchitra and Schlue, Fabian and Ares, L. and Dyachuk, V. and Stefszky, Michael and Brecht, Benjamin and Silberhorn, Christine and Sperling, Jan}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{2}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Experimental retrieval of photon statistics from click detection}}},
  doi          = {{10.1103/physreva.110.023717}},
  volume       = {{110}},
  year         = {{2024}},
}

@article{54288,
  abstract     = {{<jats:p>The ability to apply user-chosen large-scale unitary operations with high fidelity to a quantum state is key to realizing future photonic quantum technologies. Here, we realize the implementation of programmable unitary operations on up to 64 frequency-bin modes. To benchmark the performance of our system, we probe different quantum walk unitary operations, in particular, Grover walks on four-dimensional hypercubes with similarities exceeding 95% and quantum walks with 400 steps on circles and finite lines with similarities of 98%. Our results open a path toward implementing high-quality unitary operations, which can form the basis for applications in complex tasks, such as Gaussian boson sampling.</jats:p>
          <jats:sec>
            <jats:title/>
            <jats:supplementary-material>
              <jats:permissions>
                <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement>
                <jats:copyright-year>2024</jats:copyright-year>
              </jats:permissions>
            </jats:supplementary-material>
          </jats:sec>}},
  author       = {{De, Syamsundar and Ansari, Vahid and Sperling, Jan and Barkhofen, Sonja and Brecht, Benjamin and Silberhorn, Christine}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  number       = {{2}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Realization of high-fidelity unitary operations on up to 64 frequency bins}}},
  doi          = {{10.1103/physrevresearch.6.l022040}},
  volume       = {{6}},
  year         = {{2024}},
}

@article{50840,
  abstract     = {{<jats:p>Superconducting nanowire single-photon detectors (SNSPDs) have been widely used to study the discrete nature of quantum states of light in the form of photon-counting experiments. We show that SNSPDs can also be used to study continuous variables of optical quantum states by performing homodyne detection at a bandwidth of 400 kHz. By measuring the interference of a continuous-wave field of a local oscillator with the field of the vacuum state using two SNSPDs, we show that the variance of the difference in count rates is linearly proportional to the photon flux of the local oscillator over almost five orders of magnitude. The resulting shot-noise clearance of (46.0 ± 1.1) dB is the highest reported clearance for a balanced optical homodyne detector, demonstrating their potential for measuring highly squeezed states in the continuous-wave regime. In addition, we measured a CMRR = 22.4 dB. From the joint click counting statistics, we also measure the phase-dependent quadrature of a weak coherent state to demonstrate our device’s functionality as a homodyne detector.</jats:p>}},
  author       = {{Protte, Maximilian and Schapeler, Timon and Sperling, Jan and Bartley, Tim}},
  issn         = {{2837-6714}},
  journal      = {{Optica Quantum}},
  number       = {{1}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Low-noise balanced homodyne detection with superconducting nanowire single-photon detectors}}},
  doi          = {{10.1364/opticaq.502201}},
  volume       = {{2}},
  year         = {{2024}},
}

@article{44050,
  author       = {{Sperling, Jan and Agudelo, Elizabeth}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{4}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Entanglement of particles versus entanglement of fields: Independent quantum resources}}},
  doi          = {{10.1103/physreva.107.042420}},
  volume       = {{107}},
  year         = {{2023}},
}

@article{40477,
  author       = {{Sperling, Jan and Gianani, Ilaria and Barbieri, Marco and Agudelo, Elizabeth}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Detector entanglement: Quasidistributions for Bell-state measurements}}},
  doi          = {{10.1103/physreva.107.012426}},
  volume       = {{107}},
  year         = {{2023}},
}

@article{42973,
  author       = {{Lüders, Carolin and Pukrop, Matthias and Barkhausen, Franziska and Rozas, Elena and Schneider, Christian and Höfling, Sven and Sperling, Jan and Schumacher, Stefan and Aßmann, Marc}},
  issn         = {{0031-9007}},
  journal      = {{Physical Review Letters}},
  keywords     = {{General Physics and Astronomy}},
  number       = {{11}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Tracking Quantum Coherence in Polariton Condensates with Time-Resolved Tomography}}},
  doi          = {{10.1103/physrevlett.130.113601}},
  volume       = {{130}},
  year         = {{2023}},
}