@article{48349,
  abstract     = {{<jats:p>We report a titanium indiffused waveguide resonator featuring an integrated electro-optic modulator for cavity length stabilisation that produces close to 5 dB of squeezed light at 1550 nm (2.4 dB directly measured). The resonator is locked on resonance for tens of minutes with 70 mW of SH light incident on the cavity, demonstrating that photorefraction can be mitigated. Squeezed light production concurrent with cavity length stabilisation utilising the integrated EOM is demonstrated. The device demonstrates the suitability of this platform for squeezed light generation in network applications, where stabilisation to the reference field is typically necessary.</jats:p>}},
  author       = {{Stefszky, M. and vom Bruch, F. and Santandrea, M. and Ricken, R. and Quiring, V. and Eigner, C. and Herrmann, H and Silberhorn, C}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  keywords     = {{Atomic and Molecular Physics, and Optics}},
  number       = {{21}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Lithium niobate waveguide squeezer with integrated cavity length stabilisation for network applications}}},
  doi          = {{10.1364/oe.498423}},
  volume       = {{31}},
  year         = {{2023}},
}

@article{48599,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>The biexciton‐exciton emission cascade commonly used in quantum‐dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work, it focuses on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishability. It achieves this goal by selectively reducing the biexciton lifetime with an optical resonator. It demonstrates that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and twofold degenerate optical modes. The in‐depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum‐dot cavity excitation dynamics with full access to photon properties. It reports non‐trivial dependencies on system parameters and use the predictive power of the combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values, here specifically for the telecom C‐band at 1550 nm.</jats:p>}},
  author       = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}},
  issn         = {{2511-9044}},
  journal      = {{Advanced Quantum Technologies}},
  keywords     = {{tet_topic_qd}},
  publisher    = {{Wiley}},
  title        = {{{On‐Demand Indistinguishable and Entangled Photons Using Tailored Cavity Designs}}},
  doi          = {{10.1002/qute.202300142}},
  year         = {{2023}},
}

@unpublished{43246,
  abstract     = {{The biexciton-exciton emission cascade commonly used in quantum-dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work we focus on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishibility. We achieve this goal by selectively reducing the biexciton lifetime with an optical resonator. We demonstrate that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and two-fold degenerate optical modes. Our in-depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum-dot cavity excitation dynamics with full access to photon properties. We report non-trivial dependencies on system parameters and use the predictive power of our combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values in the telecom C-band at $1550\,\mathrm{nm}$.}},
  author       = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}},
  keywords     = {{tet_topic_phc, tet_topic_qd}},
  title        = {{{On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs}}},
  year         = {{2023}},
}

@article{31189,
  abstract     = {{Given a geometrically finite hyperbolic surface of infinite volume it is a
classical result of Patterson that the positive Laplace-Beltrami operator has
no $L^2$-eigenvalues $\geq 1/4$. In this article we prove a generalization of
this result for the joint $L^2$-eigenvalues of the algebra of commuting
differential operators on Riemannian locally symmetric spaces $\Gamma\backslash
G/K$ of higher rank. We derive dynamical assumptions on the $\Gamma$-action on
the geodesic and the Satake compactifications which imply the absence of the
corresponding principal eigenvalues. A large class of examples fulfilling these
assumptions are the non-compact quotients by Anosov subgroups.}},
  author       = {{Weich, Tobias and Wolf, Lasse Lennart}},
  journal      = {{Communications in Mathematical Physics}},
  title        = {{{Absence of principal eigenvalues for higher rank locally symmetric  spaces}}},
  doi          = {{https://doi.org/10.1007/s00220-023-04819-1}},
  volume       = {{403}},
  year         = {{2023}},
}

@unpublished{51206,
  abstract     = {{We present a numerical algorithm for the computation of invariant Ruelle
distributions on convex co-compact hyperbolic surfaces. This is achieved by
exploiting the connection between invariant Ruelle distributions and residues
of meromorphically continued weighted zeta functions established by the authors
together with Barkhofen (2021). To make this applicable for numerics we express
the weighted zeta as the logarithmic derivative of a suitable parameter
dependent Fredholm determinant similar to Borthwick (2014). As an additional
difficulty our transfer operator has to include a contracting direction which
we account for with techniques developed by Rugh (1992). We achieve a further
improvement in convergence speed for our algorithm in the case of surfaces with
additional symmetries by proving and applying a symmetry reduction of weighted
zeta functions.}},
  author       = {{Schütte, Philipp and Weich, Tobias}},
  booktitle    = {{arXiv:2308.13463}},
  title        = {{{Invariant Ruelle Distributions on Convex-Cocompact Hyperbolic Surfaces  -- A Numerical Algorithm via Weighted Zeta Functions}}},
  year         = {{2023}},
}

@article{49607,
  abstract     = {{In this work, we utilize thin dielectric meta-atoms placed on a silver substrate to efficiently enhance and manipulate the third-harmonic generation. We theoretically and experimentally reveal that when the structural symmetry of the meta-atom is incompatible with the lattice symmetry of an array, some generalized nonlinear geometric phases appear, which offers new possibilities for harmonic generation control beyond the accessible symmetries governed by the selection rule. The underlying mechanism is attributed to the modified rotation of the effective principal axis of a dense meta-atom array, where the strong coupling among the units gives rise to a generalized linear geometric phase modulation of the pump light. Therefore, nonlinear geometric phases carried by third-harmonic emissions are the natural result of the wave-mixing process among the modes excited at the fundamental frequency. This mechanism further points out a new strategy to predict the nonlinear geometric phases delivered by the nanostructures according to their linear responses. Our design is simple and efficient and offers alternatives for the nonlinear meta-devices that are capable of flexible photon generation and manipulation.}},
  author       = {{Liu, Bingyi and Geromel, René and Su, Zhaoxian and Guo, Kai and Wang, Yongtian and Guo, Zhongyi and Huang, Lingling and Zentgraf, Thomas}},
  issn         = {{2330-4022}},
  journal      = {{ACS Photonics}},
  keywords     = {{Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Biotechnology, Electronic, Optical and Magnetic Materials}},
  number       = {{12}},
  pages        = {{4357--4366}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Nonlinear Dielectric Geometric-Phase Metasurface with Simultaneous Structure and Lattice Symmetry Design}}},
  doi          = {{10.1021/acsphotonics.3c01163}},
  volume       = {{10}},
  year         = {{2023}},
}

@article{55901,
  author       = {{Grisard, Stefan and Trifonov, Artur V. and Rose, Hendrik and Reichhardt, Rilana and Reichelt, Matthias and Schneider, Christian and Kamp, Martin and Höfling, Sven and Bayer, Manfred and Meier, Torsten and Akimov, Ilya A.}},
  issn         = {{2330-4022}},
  journal      = {{ACS Photonics}},
  number       = {{9}},
  pages        = {{3161--3170}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Temporal Sorting of Optical Multiwave-Mixing Processes in Semiconductor Quantum Dots}}},
  doi          = {{10.1021/acsphotonics.3c00530}},
  volume       = {{10}},
  year         = {{2023}},
}

@article{42158,
  author       = {{Lüders, Carolin and Gil-Lopez, Jano and Allgaier, Markus and Brecht, Benjamin and Aßmann, Marc and Silberhorn, Christine and Bayer, Manfred}},
  issn         = {{2331-7019}},
  journal      = {{Physical Review Applied}},
  keywords     = {{General Physics and Astronomy}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Tailored Frequency Conversion Makes Infrared Light Visible for Streak Cameras}}},
  doi          = {{10.1103/physrevapplied.19.014072}},
  volume       = {{19}},
  year         = {{2023}},
}

@inproceedings{31872,
  abstract     = {{Savitch's theorem states that NPSPACE computations can be simulated in
PSPACE. We initiate the study of a quantum analogue of NPSPACE, denoted
Streaming-QCMASPACE (SQCMASPACE), where an exponentially long classical proof
is streamed to a poly-space quantum verifier. Besides two main results, we also
show that a quantum analogue of Savitch's theorem is unlikely to hold, as
SQCMASPACE=NEXP. For completeness, we introduce Streaming-QMASPACE (SQMASPACE)
with an exponentially long streamed quantum proof, and show SQMASPACE=QMA_EXP
(quantum analogue of NEXP). Our first main result shows, in contrast to the
classical setting, the solution space of a quantum constraint satisfaction
problem (i.e. a local Hamiltonian) is always connected when exponentially long
proofs are permitted. For this, we show how to simulate any Lipschitz
continuous path on the unit hypersphere via a sequence of local unitary gates,
at the expense of blowing up the circuit size. This shows quantum
error-correcting codes can be unable to detect one codeword erroneously
evolving to another if the evolution happens sufficiently slowly, and answers
an open question of [Gharibian, Sikora, ICALP 2015] regarding the Ground State
Connectivity problem. Our second main result is that any SQCMASPACE computation
can be embedded into "unentanglement", i.e. into a quantum constraint
satisfaction problem with unentangled provers. Formally, we show how to embed
SQCMASPACE into the Sparse Separable Hamiltonian problem of [Chailloux,
Sattath, CCC 2012] (QMA(2)-complete for 1/poly promise gap), at the expense of
scaling the promise gap with the streamed proof size. As a corollary, we obtain
the first systematic construction for obtaining QMA(2)-type upper bounds on
arbitrary multi-prover interactive proof systems, where the QMA(2) promise gap
scales exponentially with the number of bits of communication in the
interactive proof.}},
  author       = {{Gharibian, Sevag and Rudolph, Dorian}},
  booktitle    = {{14th Innovations in Theoretical Computer Science (ITCS)}},
  pages        = {{53:1--53:23}},
  title        = {{{Quantum space, ground space traversal, and how to embed multi-prover  interactive proofs into unentanglement}}},
  doi          = {{10.4230/LIPIcs.ITCS.2023.53}},
  volume       = {{251}},
  year         = {{2023}},
}

@article{43421,
  abstract     = {{The achievement of a flat metasurface has realized extraordinary control over light–matter interaction at the nanoscale, enabling widespread use in imaging, holography, and biophotonics. However, three-dimensional metasurfaces with the potential to provide additional light–matter manipulation flexibility attract only little interest. Here, we demonstrate a three-dimensional metasurface scheme capable of providing dual phase control through out-of-plane plasmonic resonance of L-shape antennas. Under circularly polarized excitation at a specific wavelength, the L-shape antennas with rotating orientation angle act as spatially variant three-dimensional tilted dipoles and are able to generate desire phase delay for different polarization components. Generalized Snell's law is achieved for both in-plane and out-of-plane dipole components through arranging such L-shape antennas into arrays. These three-dimensional metasurfaces suggest a route for wavefront modulation and a variety of nanophotonic applications.}},
  author       = {{Li, Tianyou and Chen, Yanjie and Wang, Yongtian and Zentgraf, Thomas and Huang, Lingling}},
  issn         = {{0003-6951}},
  journal      = {{Applied Physics Letters}},
  keywords     = {{Physics and Astronomy (miscellaneous)}},
  number       = {{14}},
  publisher    = {{AIP Publishing}},
  title        = {{{Three-dimensional dipole momentum analog based on L-shape metasurface}}},
  doi          = {{10.1063/5.0142389}},
  volume       = {{122}},
  year         = {{2023}},
}

@article{37280,
  author       = {{Rose, Hendrik and Vasil'ev, A. N. and Tikhonova, O. V. and Meier, Torsten and Sharapova, Polina}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Quantum-optical excitations of semiconductor nanostructures in a microcavity using a two-band model and a single-mode quantum field}}},
  doi          = {{10.1103/physreva.107.013703}},
  volume       = {{107}},
  year         = {{2023}},
}

@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}},
}

@inproceedings{20841,
  author       = {{Gharibian, Sevag and Watson, James and Bausch, Johannes}},
  booktitle    = {{Proceedings of the 40th International Symposium on Theoretical Aspects of Computer Science (STACS)}},
  pages        = {{54:1--54:21}},
  title        = {{{The Complexity of Translationally Invariant Problems beyond Ground State Energies}}},
  doi          = {{https://doi.org/10.4230/LIPIcs.STACS.2023.54}},
  volume       = {{254}},
  year         = {{2023}},
}

@article{44044,
  abstract     = {{Dispersion is present in every optical setup and is often an undesired effect, especially in nonlinear-optical experiments where ultrashort laser pulses are needed. Typically, bulky pulse compressors consisting of gratings or prisms are used
to address this issue by precompensating the dispersion of the optical components. However, these devices are only able to compensate for a part of the dispersion (second-order dispersion). Here, we present a compact pulse-shaping device that uses plasmonic metasurfaces to apply an arbitrarily designed spectral phase delay allowing for a full dispersion control. Furthermore, with specific phase encodings, this device can be used to temporally reshape the incident laser pulses into more complex pulse forms such as a double pulse. We verify the performance of our device by using an SHG-FROG measurement setup together with a retrieval algorithm to extract the dispersion that our device applies to an incident laser pulse.}},
  author       = {{Geromel, René and Georgi, Philip and Protte, Maximilian and Lei, Shiwei and Bartley, Tim and Huang, Lingling and Zentgraf, Thomas}},
  issn         = {{1530-6984}},
  journal      = {{Nano Letters}},
  keywords     = {{Mechanical Engineering, Condensed Matter Physics, General Materials Science, General Chemistry, Bioengineering}},
  number       = {{8}},
  pages        = {{3196 -- 3201}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Compact Metasurface-Based Optical Pulse-Shaping Device}}},
  doi          = {{10.1021/acs.nanolett.2c04980}},
  volume       = {{23}},
  year         = {{2023}},
}

@article{45485,
  author       = {{Kruse, Stephan and Serino, Laura and Folge, Patrick Fabian and Echeverria Oviedo, Dana and Bhattacharjee, Abhinandan and Stefszky, Michael and Scheytt, J. Christoph and Brecht, Benjamin and Silberhorn, Christine}},
  issn         = {{1041-1135}},
  journal      = {{IEEE Photonics Technology Letters}},
  keywords     = {{Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials}},
  number       = {{14}},
  pages        = {{769--772}},
  publisher    = {{Institute of Electrical and Electronics Engineers (IEEE)}},
  title        = {{{A Pulsed Lidar System With Ultimate Quantum Range Accuracy}}},
  doi          = {{10.1109/lpt.2023.3277515}},
  volume       = {{35}},
  year         = {{2023}},
}

@inproceedings{43192,
  abstract     = {{The nonlinear optical response of an ensemble of semiconductor quantum dots is analyzed by wave-mixing processes, where we focus on four-wave mixing with two incident pulses. Wave-mixing experiments are often described with semiclassical models, where the light is modeled classically and the material quantum mechanically. Here, however, we use a fully quantized model, where the light is given by a quantum state of light. Quantum light involves more degrees of freedom than classical light as e.g., its photon statistics and quantum correlations, which is a promising resource for quantum devices, such as quantum memories. The light-matter interaction is treated with a Jaynes-Cummings type model and the quantum field is given by a single mode since the quantum dots are embedded in a microcavity. We present numerical simulations of the four-wave-mixing response of a homogeneous system for pulse sequences and find a significant dependence of the result on the photon statistics of the incident pulses. The model constitutes a problem with a large state space which arises from the frequency distribution of the transition energies of the inhomogeneously broadened quantum dot ensemble that is coupled with a quantum light mode. Here we approximate the dynamics by summing over individual quantum dot-microcavity systems. Photon echoes arising from the excitation with different quantum states of light are simulated and compared.}},
  author       = {{Rose, Hendrik and Grisard, S. and Trifonov, A. V. and Reichhardt, R. and Reichelt, Matthias and Bayer, M. and Akimov, I. A.  and Meier, Torsten}},
  booktitle    = {{Ultrafast Phenomena and Nanophotonics XXVII}},
  publisher    = {{SPIE}},
  title        = {{{Theoretical analysis of four-wave mixing on semiconductor quantum dot ensembles with quantum light}}},
  doi          = {{10.1117/12.2647700}},
  volume       = {{12419}},
  year         = {{2023}},
}

@article{45868,
  abstract     = {{Perfect vector vortex beams (PVVBs) have attracted considerable interest due to their peculiar optical features. PVVBs are typically generated through the superposition of perfect vortex beams, which suffer from the limited number of topological charges (TCs). Furthermore, dynamic control of PVVBs is desirable and has not been reported. We propose and experimentally demonstrate hybrid grafted perfect vector vortex beams (GPVVBs) and their dynamic control. Hybrid GPVVBs are generated through the superposition of grafted perfect vortex beams with a multifunctional metasurface. The generated hybrid GPVVBs possess spatially variant rates of polarization change due to the involvement of more TCs. Each hybrid GPVVB includes different GPVVBs in the same beam, adding more design flexibility. Moreover, these beams are dynamically controlled with a rotating half waveplate. The generated dynamic GPVVBs may find applications in the fields where dynamic control is in high demand, including optical encryption, dense data communication, and multiple particle manipulation.}},
  author       = {{Ahmed, Hammad and Ansari, Muhammad Afnan and Li, Yan and Zentgraf, Thomas and Mehmood, Muhammad Qasim and Chen, Xianzhong}},
  issn         = {{2041-1723}},
  journal      = {{Nature Communications}},
  keywords     = {{General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary}},
  number       = {{1}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{Dynamic control of hybrid grafted perfect vector vortex beams}}},
  doi          = {{10.1038/s41467-023-39599-8}},
  volume       = {{14}},
  year         = {{2023}},
}

@article{45850,
  abstract     = {{Interference between single photons is key for many quantum optics experiments and applications in quantum technologies, such as quantum communication or computation. It is advantageous to operate the systems at telecommunication wavelengths and to integrate the setups for these applications in order to improve stability, compactness and scalability. A new promising material platform for integrated quantum optics is lithium niobate on insulator (LNOI). Here, we realise Hong-Ou-Mandel (HOM) interference between telecom photons from an engineered parametric down-conversion source in an LNOI directional coupler. The coupler has been designed and fabricated in house and provides close to perfect balanced beam splitting. We obtain a raw HOM visibility of (93.5 ± 0.7) %, limited mainly by the source performance and in good agreement with off-chip measurements. This lays the foundation for more sophisticated quantum experiments in LNOI.}},
  author       = {{Babel, Silia and Bollmers, Laura and Massaro, Marcello and Luo, Kai Hong and Stefszky, Michael and Pegoraro, Federico and Held, Philip and Herrmann, Harald and Eigner, Christof and Brecht, Benjamin and Padberg, Laura and Silberhorn, Christine}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  keywords     = {{Atomic and Molecular Physics, and Optics}},
  number       = {{14}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Demonstration of Hong-Ou-Mandel interference in an LNOI directional coupler}}},
  doi          = {{10.1364/oe.484126}},
  volume       = {{31}},
  year         = {{2023}},
}