@article{56267,
  author       = {{Serino, Laura and Ridder, Werner and Bhattacharjee, Abhinandan and Gil López, Jano and Brecht, Benjamin and Silberhorn, Christine}},
  issn         = {{2837-6714}},
  journal      = {{Optica Quantum}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Orchestrating time and color: a programmable source of high-dimensional entanglement}}},
  doi          = {{10.1364/opticaq.532334}},
  year         = {{2024}},
}

@article{62849,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>An on-demand source of bright entangled photon pairs is desirable for quantum key distribution (QKD) and quantum repeaters. The leading candidate to generate such pairs is based on spontaneous parametric down-conversion (SPDC) in non-linear crystals. However, its pair extraction efficiency is limited to 0.1% when operating at near-unity fidelity due to multiphoton emission at high brightness. Quantum dots in photonic nanostructures can in principle overcome this limit, but the devices with high entanglement fidelity (99%) have low pair extraction efficiency (0.01%). Here, we show a measured peak entanglement fidelity of 97.5% ± 0.8% and pair extraction efficiency of 0.65% from an InAsP quantum dot in an InP photonic nanowire waveguide. We show that the generated oscillating two-photon Bell state can establish a secure key for peer-to-peer QKD. Using our time-resolved QKD scheme alleviates the need to remove the quantum dot energy splitting of the intermediate exciton states in the biexciton-exciton cascade.</jats:p>}},
  author       = {{Pennacchietti, Matteo and Cunard, Brady and Nahar, Shlok and Zeeshan, Mohd and Gangopadhyay, Sayan and Poole, Philip J. and Dalacu, Dan and Fognini, Andreas and Jöns, Klaus and Zwiller, Val and Jennewein, Thomas and Lütkenhaus, Norbert and Reimer, Michael E.}},
  issn         = {{2399-3650}},
  journal      = {{Communications Physics}},
  number       = {{1}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{Oscillating photonic Bell state from a semiconductor quantum dot for quantum key distribution}}},
  doi          = {{10.1038/s42005-024-01547-3}},
  volume       = {{7}},
  year         = {{2024}},
}

@inproceedings{62852,
  author       = {{Gyger, Samuel and Tao, Max and Colangelo, Marco and Christen, Ian and Larocque, Hugo and Zichi, Julian and Schweickert, Lucas and Elshaari, Ali and Steinhauer, Stephan and Covre da Silva, Saimon and Rastelli, Armando and Sattari, Hamed and Chong, Gregory and Pétremand, Yves and Prieto, Ivan and Yu, Yang and Ghadimi, Amir and Englund, Dirk and Jöns, Klaus and Zwiller, Val and Errando Herranz, Carlos}},
  booktitle    = {{Quantum Computing, Communication, and Simulation IV}},
  editor       = {{Hemmer, Philip R. and Migdall, Alan L.}},
  publisher    = {{SPIE}},
  title        = {{{Integrating superconducting single-photon detectors into active photonic circuits}}},
  doi          = {{10.1117/12.3009736}},
  year         = {{2024}},
}

@inproceedings{62850,
  author       = {{Mikitta, Telsche and Cutuk, Ana and Jetter, Michael and Michler, Peter and Jöns, Klaus and Kahle, Hermann}},
  booktitle    = {{Vertical External Cavity Surface Emitting Lasers (VECSELs) XIII}},
  editor       = {{Keller, Ursula}},
  publisher    = {{SPIE}},
  title        = {{{Membrane external-cavity surface-emitting lasers (MECSELs) optimized for double-side-pumping: a first fundamental single-side pumping characterization}}},
  doi          = {{10.1117/12.3002481}},
  year         = {{2024}},
}

@article{52876,
  author       = {{Arends, Christian and Wolf, Lasse Lennart and Meinecke, Jasmin and Barkhofen, Sonja and Weich, Tobias and Bartley, Tim}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  keywords     = {{General Physics and Astronomy}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Decomposing large unitaries into multimode devices of arbitrary size}}},
  doi          = {{10.1103/physrevresearch.6.l012043}},
  volume       = {{6}},
  year         = {{2024}},
}

@article{62868,
  abstract     = {{<jats:p>We theoretically investigate strategies for the deterministic creation of trains of time-bin entangled photons using an individual quantum emitter described by a Λ-type electronic system. We explicitly demonstrate the theoretical generation of linear cluster states with substantial numbers of entangled photonic qubits in full microscopic numerical simulations. The underlying scheme is based on the manipulation of ground state coherences through precise optical driving. One important finding is that the most easily accessible quality metrics, the achievable rotation fidelities, fall short in assessing the actual quantum correlations of the emitted photons in the face of losses. To address this, we explicitly calculate stabilizer generator expectation values as a superior gauge for the quantum properties of the generated many-photon state. With widespread applicability in other emitter and excitation–emission schemes also, our work lays the conceptual foundations for an in-depth practical analysis of time-bin entanglement based on full numerical simulations with predictive capabilities for realistic systems and setups, including losses and imperfections. The specific results shown in the present work illustrate that with controlled minimization of losses and realistic system parameters for quantum-dot type systems, useful linear cluster states of significant lengths can be generated in the calculations, discussing the possibility of scalability for quantum information processing endeavors.</jats:p>}},
  author       = {{Bauch, David and Köcher, Nikolas and Heinisch, Nils and Schumacher, Stefan}},
  issn         = {{2835-0103}},
  journal      = {{APL Quantum}},
  number       = {{3}},
  publisher    = {{AIP Publishing}},
  title        = {{{Time-bin entanglement in the deterministic generation of linear photonic cluster states}}},
  doi          = {{10.1063/5.0214197}},
  volume       = {{1}},
  year         = {{2024}},
}

@article{62853,
  abstract     = {{<jats:title>Abstract</jats:title>
                  <jats:p>Developing coherent excitation methods for quantum emitters ensuring high brightness, optimal single‐photon purity and indistinguishability of the emitted photons has been a key challenge in the past years. While various methods have been proposed and explored, they all have specific advantages and disadvantages. This study investigates the dynamics of the recent swing‐up scheme as an excitation method for a two‐level system and its performance in single‐photon generation. By applying two far red‐detuned laser pulses, the two‐level system can be prepared in the excited state with near‐unity fidelity. The successful operation and coherent character of this technique are demonstrated using a semiconductor quantum dot (QD). Moreover, the multi‐dimensional parameter space of the two laser pulses is explored to analyze its impact on excitation fidelity. Finally, the performance of the scheme as an excitation method for generating high‐quality single photons is analyzed. The swing‐up scheme itself proves effective, exhibiting nearly perfect single‐photon purity, while the observed indistinguishability in the studied sample is limited by the influence of the inevitable high excitation powers on the semiconductor environment of the quantum dot.</jats:p>}},
  author       = {{Boos, Katarina and Sbresny, Friedrich and Kim, Sang Kyu and Kremser, Malte and Riedl, Hubert and Bopp, Frederik W. and Rauhaus, William and Scaparra, Bianca and Jöns, Klaus and Finley, Jonathan J. and Müller, Kai and Hanschke, Lukas}},
  issn         = {{2511-9044}},
  journal      = {{Advanced Quantum Technologies}},
  number       = {{4}},
  publisher    = {{Wiley}},
  title        = {{{Coherent Swing‐Up Excitation for Semiconductor Quantum Dots}}},
  doi          = {{10.1002/qute.202300359}},
  volume       = {{7}},
  year         = {{2024}},
}

@unpublished{62858,
  abstract     = {{Phonons in solid-state quantum emitters play a crucial role in their performance as photon sources in quantum technology. For resonant driving, phonons dampen the Rabi oscillations resulting in reduced preparation fidelities. The phonon spectral density, which quantifies the strength of the carrier-phonon interaction, is non-monotonous as a function of energy. As one of the most prominent consequences, this leads to the reappearance of Rabi rotations for increasing pulse power, which was theoretically predicted in Phys. Rev. Lett. 98, 227403 (2007). In this paper we present the experimental demonstration of the reappearance of Rabi rotations.}},
  author       = {{Hanschke, L. and Bracht, T. K. and Schöll, E. and Bauch, David and Berger, Eva and Kallert, Patricia and Peter, M. and Garcia, A. J. and Silva, S. F. Covre da and Manna, S. and Rastelli, A. and Schumacher, Stefan and Reiter, D. E. and Jöns, Klaus}},
  booktitle    = {{arXiv:2409.19167}},
  title        = {{{Experimental measurement of the reappearance of Rabi rotations in semiconductor quantum dots}}},
  year         = {{2024}},
}

@unpublished{62856,
  abstract     = {{On-chip emitters that can generate single and entangled photons are essential building blocks for developing photonic quantum information processing technologies in a scalable fashion. Semiconductor quantum dots (QDs) are attractive candidates that emit high-quality quantum states of light on demand, however at a rate limited by their spontaneous radiative lifetime. In this study, we utilize the Purcell effect to demonstrate up to a 38-fold enhancement in the emission rate of InAs QDs by coupling them to metal-clad GaAs nanopillars. These cavities, featuring a sub-wavelength mode volume of 4.5x10-4 (λ/n)3 and low quality factor of 62, enable Purcell-enhanced single-photon emission across a large bandwidth of 15 nm. The broadband nature of the cavity eliminates the need for implementing tuning mechanisms typically required to achieve QD-cavity resonance, thus relaxing fabrication constraints. Ultimately, this QD-cavity architecture represents a significant stride towards developing solid-state quantum emitters generating near-ideal single-photon states at GHz-level repetition rates.}},
  author       = {{Jöns, Klaus}},
  title        = {{{Purcell-enhanced single-photon emission from InAs/GaAs quantum dots coupled to broadband cylindrical nanocavities}}},
  year         = {{2024}},
}

@article{63048,
  title        = {{{High-throughput antibody screening with high-quality factor nanophotonics and bioprinting}}},
  doi          = {{10.48550/ARXIV.2411.18557}},
  year         = {{2024}},
}

@misc{63047,
  author       = {{Güsken, Nicholas Alexander}},
  title        = {{{Schottky-barrier type infrared photodetector }}},
  year         = {{2024}},
}

@article{63044,
  author       = {{Hoessbacher, C. and Baeuerle, B. and Del Medico, N. and De Leo, E. and Güsken, Nicholas Alexander and Heni, W. and Langenbach, A. and Tedaldi, V.}},
  issn         = {{2732-4494}},
  journal      = {{IET Conference Proceedings}},
  number       = {{34}},
  pages        = {{1606--1608}},
  publisher    = {{Institution of Engineering and Technology (IET)}},
  title        = {{{Plasmonic modulators: bringing a new light to silicon}}},
  doi          = {{10.1049/icp.2023.2642}},
  volume       = {{2023}},
  year         = {{2024}},
}

@article{63049,
  author       = {{Güsken, Nicholas Alexander and Brongersma, Mark L.}},
  issn         = {{2791-1748}},
  journal      = {{Photonics Insights}},
  number       = {{4}},
  publisher    = {{Shanghai Institute of Optics and Fine Mechanics}},
  title        = {{{Electrifying the field of metasurface optics}}},
  doi          = {{10.3788/pi.2024.c08}},
  volume       = {{3}},
  year         = {{2024}},
}

@article{53202,
  abstract     = {{At large scales, quantum systems may become advantageous over their classical counterparts at performing certain tasks. Developing tools to analyze these systems at the relevant scales, in a manner consistent with quantum mechanics, is therefore critical to benchmarking performance and characterizing their operation. While classical computational approaches cannot perform like-for-like computations of quantum systems beyond a certain scale, classical high-performance computing (HPC) may nevertheless be useful for precisely these characterization and certification tasks. By developing open-source customized algorithms using high-performance computing, we perform quantum tomography on a megascale quantum photonic detector covering a Hilbert space of 106. This requires finding 108 elements of the matrix corresponding to the positive operator valued measure (POVM), the quantum description of the detector, and is achieved in minutes of computation time. Moreover, by exploiting the structure of the problem, we achieve highly efficient parallel scaling, paving the way for quantum objects up to a system size of 1012 elements to be reconstructed using this method. In general, this shows that a consistent quantum mechanical description of quantum phenomena is applicable at everyday scales. More concretely, this enables the reconstruction of large-scale quantum sources, processes and detectors used in computation and sampling tasks, which may be necessary to prove their nonclassical character or quantum computational advantage.}},
  author       = {{Schapeler, Timon and Schade, Robert and Lass, Michael and Plessl, Christian and Bartley, Tim}},
  journal      = {{Quantum Science and Technology}},
  number       = {{1}},
  publisher    = {{IOP Publishing}},
  title        = {{{Scalable quantum detector tomography by high-performance computing}}},
  doi          = {{10.1088/2058-9565/ad8511}},
  volume       = {{10}},
  year         = {{2024}},
}

@article{63219,
  abstract     = {{<jats:p>We introduce the framework of Bayesian relative belief that directly evaluates whether or not the experimental data at hand support a given hypothesis regarding a quantum system by directly comparing the prior and posterior probabilities for the hypothesis. In model-dimension certification tasks, we show that the relative-belief procedure typically chooses Hilbert spaces that are never smaller in dimension than those selected from optimizing a broad class of information criteria, including Akaike's criterion. As a concrete and focused exposition of this powerful evidence-based technique, we apply the relative-belief procedure to an important application: . In particular, just by comparing prior and posterior probabilities based on data, we demonstrate its capability of tracking multiphoton emissions using (realistically lossy) single-photon detectors in order to assess the actual quality of photon sources without making  assumptions, thereby reliably safeguarding source integrity for general quantum-information and communication tasks with Bayesian reasoning. Finally, we discuss how relative belief can be exploited to carry out parametric model certification and estimate the total dimension of the quantum state for the combined (measured) physical and interacting external systems described by the Tavis-Cummings model.</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       = {{Teo, Y. S. and Shringarpure, S. U. and Jeong, H. and Prasannan, Nidhin and Brecht, Benjamin and Silberhorn, Christine and Evans, M. and Mogilevtsev, D. and Sánchez-Soto, L. L.}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Relative-belief inference in quantum information theory}}},
  doi          = {{10.1103/physreva.110.012231}},
  volume       = {{110}},
  year         = {{2024}},
}

@article{63216,
  abstract     = {{<jats:p>The characterization of the complex spectral amplitude, that is, the spectrum and spectral phase, of single-photon-level light fields is a crucial capability for modern photonic quantum technologies. Since established pulse characterization techniques are not applicable at low intensities, alternative approaches are required. Here, we demonstrate the retrieval of the complex spectral amplitude of single-photon-level light pulses through measuring their chronocyclic <jats:italic toggle="yes">Q</jats:italic> −function. Our approach draws inspiration from quantum state tomography by exploiting the analogy between quadrature phase space and time-frequency phase space. In the experiment, we perform time-frequency projections with a quantum pulse gate (QPG), which directly yield the chronocyclic <jats:italic toggle="yes">Q</jats:italic> −function. We evaluate the complex spectral amplitude from the measured chronocyclic <jats:italic toggle="yes">Q</jats:italic> −function data with maximum likelihood estimation (MLE), which is the established technique for quantum state tomography. The MLE yields not only an unambigious estimate of the complex spectral amplitude of the state under test that does not require any <jats:italic toggle="yes">a priori</jats:italic> information, but also allows for, in principle, estimating the spectral-temporal coherence properties of the state. Our method accurately recovers features such as jumps in the spectral phase and is resistant against regions with zero spectral intensity, which makes it immediately beneficial for classical pulse characterization problems.</jats:p>}},
  author       = {{Bhattacharjee, Abhinandan and Folge, Patrick Fabian and Serino, Laura Maria and Řeháček, Jaroslav and Hradil, Zdeněk and Silberhorn, Christine and Brecht, Benjamin}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  number       = {{3}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Pulse characterization at the single-photon level through chronocyclic <i>Q</i>-function measurements}}},
  doi          = {{10.1364/oe.540125}},
  volume       = {{33}},
  year         = {{2024}},
}

@article{63220,
  abstract     = {{<jats:p>Identifying a reasonably small Hilbert space that completely describes an unknown quantum state is crucial for efficient quantum information processing. We introduce a general dimension-certification protocol for both discrete and continuous variables that is fully evidence based, relying solely on the experimental data collected and no other unjustified assumptions whatsoever. Using the Bayesian concept of relative belief, we take the effective dimension of the state as the smallest one such that the posterior probability is larger than the prior, as dictated by the data. The posterior probabilities associated with the relative-belief ratios measure the strength of the evidence provide by these ratios so that we can assess whether there is weak or strong evidence in favor or against a particular dimension. Using experimental data from spectral-temporal and polarimetry measurements, we demonstrate how to correctly assign Bayesian plausible error bars for the obtained effective dimensions. This makes relative belief a conservative and easy-to-use model-selection method for any experiment.</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       = {{Teo, Y. S. and Shringarpure, S. U. and Jeong, H. and Prasannan, Nidhin and Brecht, Benjamin and Silberhorn, Christine and Evans, M. and Mogilevtsev, D. and Sánchez-Soto, L. L.}},
  issn         = {{0031-9007}},
  journal      = {{Physical Review Letters}},
  number       = {{5}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Evidence-Based Certification of Quantum Dimensions}}},
  doi          = {{10.1103/physrevlett.133.050204}},
  volume       = {{133}},
  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{63218,
  abstract     = {{<jats:p>Linear optical quantum networks, consisting of a quantum input state and a multiport interferometer, are an important building block for many quantum technological concepts, e.g., Gaussian boson sampling. Here, we propose the implementation of such networks based on frequency conversion by utilizing a so-called multioutput quantum pulse gate (MQPG). This approach allows the resource-efficient and therefore scalable implementation of frequency-bin-based, fully programmable interferometers in a single spatial and polarization mode. Quantum input states for this network can be provided by utilizing the strong frequency entanglement of a type-0 parametric down-conversion (PDC) source. Here, we develop a theoretical framework to describe linear networks based on an MQPG and PDC and utilize it to investigate the limits and scalabilty of our approach.</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       = {{Folge, Patrick Fabian and Stefszky, Michael and Brecht, Benjamin and Silberhorn, Christine}},
  issn         = {{2691-3399}},
  journal      = {{PRX Quantum}},
  number       = {{4}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{A Framework for Fully Programmable Frequency-Encoded Quantum Networks Harnessing Multioutput Quantum Pulse Gates}}},
  doi          = {{10.1103/prxquantum.5.040329}},
  volume       = {{5}},
  year         = {{2024}},
}

@article{63217,
  abstract     = {{<jats:p>We demonstrate a high-dimensional mode-sorter for single photons based on a multi-output quantum pulse gate, which we can program to switch between different temporal-mode encodings including pulse modes, frequency bins, time bins, and their superpositions. This device can facilitate practical realizations of quantum information applications such as high-dimensional quantum key distribution and thus enables secure communication with enhanced information capacity. We characterize the mode-sorter through a detector tomography in 3 and 5 dimensions and find a fidelity up to 0.958 ± 0.030 at the single-photon level.</jats:p>}},
  author       = {{Serino, Laura Maria and Eigner, Christof and Brecht, Benjamin and Silberhorn, Christine}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  number       = {{3}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Programmable time-frequency mode-sorting of single photons with a multi-output quantum pulse gate}}},
  doi          = {{10.1364/oe.544206}},
  volume       = {{33}},
  year         = {{2024}},
}