TY - JOUR AB - Ferroelectric domain wall (DW) conductivity (DWC) can be attributed to two separate mechanisms: (a) the injection/ejection of charge carriers across the Schottky barrier formed at the (metal-)electrode-DW junction and (b) the transport of those charge carriers along the DW. Current-voltage (I-U) characteristics, recorded at variable temperatures from LiNbO3 (LNO) DWs, are clearly able to differentiate between these two contributions. Practically, they allow us to directly quantify the physical parameters relevant to the two mechanisms (a) and (b) mentioned above. These are, for example, the resistance of the DW, the saturation current, the ideality factor, and the Schottky barrier height of the electrode-DW junction. Furthermore, the activation energies needed to initiate the thermally activated electronic transport along the DWs can be extracted. In addition, we show that electronic transport along LNO DWs can be elegantly viewed and interpreted in an adapted semiconductor picture based on a double-diode, double-resistor equivalent-circuit model, the R2D2 model. Finally, our R2D2 model was checked for its universality by successfully fitting the I-U curves of not only z-cut LNO bulk DWs, but equally of z-cut thin-film LNO DWs, and of x-cut thin-film DWs as reported in literature. AU - Zahn, Manuel AU - Beyreuther, Elke AU - Kiseleva, Iuliia AU - Lotfy, Ahmed Samir AU - McCluskey, Conor J. AU - Maguire, Jesi R. AU - Suna, Ahmet AU - Rüsing, Michael AU - Gregg, J. Marty AU - Eng, Lukas M. ID - 51156 IS - 2 JF - Physical Review Applied KW - General Physics and Astronomy SN - 2331-7019 TI - Equivalent-circuit model that quantitatively describes domain-wall conductivity in ferroelectric lithium VL - 21 ER - TY - JOUR AU - Babai-Hemati, Jonas AU - vom Bruch, Felix AU - Herrmann, Harald AU - Silberhorn, Christine ID - 51339 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Tailored second harmonic generation inTi-diffused PPLN waveguides usingmicro-heaters ER - TY - JOUR AB - In real photonic quantum systems losses are an unavoidable factor limiting the scalability to many modes and particles, restraining their application in fields as quantum information and communication. For this reason, a considerable amount of engineering effort has been taken in order to improve the quality of particle sources and system components. At the same time, data analysis and collection methods based on post-selection have been used to mitigate the effect of particle losses. This has allowed for investigating experimentally multi-particle evolutions where the observer lacks knowledge about the system's intermediate propagation states. Nonetheless, the fundamental question how losses affect the behaviour of the surviving subset of a multi-particle system has not been investigated so far. For this reason, here we study the impact of particle losses in a quantum walk of two photons reconstructing the output probability distributions for one photon conditioned on the loss of the other in a known mode and temporal step of our evolution network. We present the underlying theoretical scheme that we have devised in order to model controlled particle losses, we describe an experimental platform capable of implementing our theory in a time multiplexing encoding. In the end we show how localized particle losses change the output distributions without altering their asymptotic spreading properties. Finally we devise a quantum civilization problem, a two walker generalisation of single particle recurrence processes. AU - Pegoraro, Federico AU - Held, Philip AU - Barkhofen, Sonja AU - Brecht, Benjamin AU - Silberhorn, Christine ID - 42648 IS - 3 JF - Physica Scripta SN - 0031-8949 TI - Dynamic conditioning of two particle discrete-time quantum walks VL - 98 ER - TY - JOUR AU - Serino, Laura AU - Gil López, Jano AU - Stefszky, Michael AU - Ricken, Raimund AU - Eigner, Christof AU - Brecht, Benjamin AU - Silberhorn, Christine ID - 44081 IS - 2 JF - PRX Quantum KW - General Physics and Astronomy KW - Mathematical Physics KW - Applied Mathematics KW - Electronic KW - Optical and Magnetic Materials KW - Electrical and Electronic Engineering KW - General Computer Science SN - 2691-3399 TI - Realization of a Multi-Output Quantum Pulse Gate for Decoding High-Dimensional Temporal Modes of Single-Photon States VL - 4 ER - TY - JOUR AU - Kruse, Stephan AU - Serino, Laura AU - Folge, Patrick Fabian AU - Echeverria Oviedo, Dana AU - Bhattacharjee, Abhinandan AU - Stefszky, Michael AU - Scheytt, J. Christoph AU - Brecht, Benjamin AU - Silberhorn, Christine ID - 45485 IS - 14 JF - IEEE Photonics Technology Letters KW - Electrical and Electronic Engineering KW - Atomic and Molecular Physics KW - and Optics KW - Electronic KW - Optical and Magnetic Materials SN - 1041-1135 TI - A Pulsed Lidar System With Ultimate Quantum Range Accuracy VL - 35 ER - TY - JOUR AB - 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. AU - Babel, Silia AU - Bollmers, Laura AU - Massaro, Marcello AU - Luo, Kai Hong AU - Stefszky, Michael AU - Pegoraro, Federico AU - Held, Philip AU - Herrmann, Harald AU - Eigner, Christof AU - Brecht, Benjamin AU - Padberg, Laura AU - Silberhorn, Christine ID - 45850 IS - 14 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Demonstration of Hong-Ou-Mandel interference in an LNOI directional coupler VL - 31 ER - TY - JOUR AB - This work reports a fully guided setup for single-mode squeezing on integrated titanium-indiffused periodically poled nonlinear resonators. A continuous-wave laser beam is delivered and the squeezed field is collected by single-mode fibers; up to −3.17(9) dB of useful squeezing is available in fibers. To showcase the usefulness of such a fiber-coupled device, we applied the generated squeezed light in a fiber-based phase sensing experiment, showing a quantum enhancement in the signal-to-noise ratio of 0.35 dB. Moreover, our investigation of the effect of photorefraction on the cavity resonance condition suggests that it causes system instabilities at high powers. AU - Domeneguetti, Renato AU - Stefszky, Michael AU - Herrmann, Harald AU - Silberhorn, Christine AU - Andersen, Ulrik L. AU - Neergaard-Nielsen, Jonas S. AU - Gehring, Tobias ID - 46138 IS - 11 JF - Optics Letters KW - Atomic and Molecular Physics KW - and Optics SN - 0146-9592 TI - Fully guided and phase locked Ti:PPLN waveguide squeezing for applications in quantum sensing VL - 48 ER - TY - JOUR AB - 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. AU - Stefszky, M. AU - vom Bruch, F. AU - Santandrea, M. AU - Ricken, R. AU - Quiring, V. AU - Eigner, C. AU - Herrmann, H AU - Silberhorn, C ID - 48349 IS - 21 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Lithium niobate waveguide squeezer with integrated cavity length stabilisation for network applications VL - 31 ER - TY - JOUR AU - Meyer-Scott, Evan AU - Prasannan, Nidhin AU - Dhand, Ish AU - Eigner, Christof AU - Quiring, Viktor AU - Barkhofen, Sonja AU - Brecht, Benjamin AU - Plenio, Martin B. AU - Silberhorn, Christine ID - 40273 IS - 15 JF - Physical Review Letters KW - General Physics and Astronomy SN - 0031-9007 TI - Scalable Generation of Multiphoton Entangled States by Active Feed-Forward and Multiplexing VL - 129 ER - TY - CONF AB - We demonstrate theoretically and experimentally complex correlations in the photon numbers of two-mode quantum states using measurement-induced nonlinearity. For this, we combine the interference of coherent states and single photons with photon sub-traction. AU - Meier, Torsten AU - Hoepker, Jan Philipp AU - Protte, Maximilian AU - Eigner, Christof AU - Silberhorn, Christine AU - Sharapova, Polina R. AU - Sperling, Jan AU - Bartley, Tim ID - 43744 SN - 978-1-957171-05-0 T2 - Conference on Lasers and Electro-Optics: Applications and Technology TI - Two-Mode Photon-Number Correlations Created by Measurement-Induced Nonlinearity ER - TY - JOUR AB - We study the DC conductivity in potassium titanyl phosphate (KTiOPO4, KTP) and its isomorphs KTiOAsO4 (KTA) and Rb1%K99%TiOPO4 (RKTP) and introduce a method by which to reduce the overall ionic conductivity in KTP by a potassium nitrate treatment. Furthermore, we create so-called gray tracking in KTP and investigate the ionic conductivity in theses areas. A local unintended reduction of the ionic conductivity is observed in the gray-tracked regions, which also induce additional optical absorption in the material. We show that a thermal treatment in an oxygen-rich atmosphere removes the gray tracking and brings the ionic conductivity as well as the optical transmission back to the original level. These studies can help to choose the best material and treatment for specific applications. AU - Padberg, Laura AU - Quiring, Viktor AU - Bocchini, Adriana AU - Santandrea, Matteo AU - Gerstmann, Uwe AU - Schmidt, Wolf Gero AU - Silberhorn, Christine AU - Eigner, Christof ID - 33484 JF - Crystals SN - 2073-4352 TI - DC Ionic Conductivity in KTP and Its Isomorphs: Properties, Methods for Suppression, and Its Connection to Gray Tracking VL - 12 ER - TY - JOUR AU - Prasannan, Nidhin AU - Sperling, Jan AU - Brecht, Benjamin AU - Silberhorn, Christine ID - 34884 IS - 26 JF - Physical Review Letters KW - General Physics and Astronomy SN - 0031-9007 TI - Direct Measurement of Higher-Order Nonlinear Polarization Squeezing VL - 129 ER - TY - JOUR AB - Quantum walks function as essential means to implement quantum simulators, allowing one to study complex and often directly inaccessible quantum processes in controllable systems. In this contribution, the notion of a driven Gaussian quantum walk is introduced. In contrast to typically considered quantum walks in optical settings, we describe the operation of the walk in terms of a nonlinear map rather than a unitary operation, e.g., by replacing a beam-splitter-type coin with a two-mode squeezer, being a process that is controlled and driven by a pump field. This opens previously unattainable possibilities for quantum walks that include nonlinear elements as core components of their operation, vastly extending their range of applications. A full framework for driven Gaussian quantum walks is developed, including methods to dynamically characterize nonlinear, quantum, and quantum-nonlinear effects. Moreover, driven Gaussian quantum walks are compared with their classically interfering and linear counterparts, which are based on classical coherence of light rather than quantum superpositions. In particular, the generation and boost of highly multimode entanglement, squeezing, and other quantum effects are studied over the duration of the nonlinear walk. Importantly, we prove the quantumness of the evolution itself, regardless of the input state. A scheme for an experimental realization is proposed. Furthermore, nonlinear properties of driven Gaussian quantum walks are explored, such as amplification that leads to an ever increasing number of correlated quantum particles, constituting a source of new walkers during the walk. Therefore, a concept for quantum walks is proposed that leads to—and even produces—directly accessible quantum phenomena, and that renders the quantum simulation of nonlinear processes possible. AU - Held, Philip AU - Engelkemeier, Melanie AU - De, Syamsundar AU - Barkhofen, Sonja AU - Sperling, Jan AU - Silberhorn, Christine ID - 30921 IS - 4 JF - Physical Review A SN - 2469-9926 TI - Driven Gaussian quantum walks VL - 105 ER - TY - JOUR AU - Santandrea, Matteo AU - Stefszky, Michael AU - Silberhorn, Christine ID - 26218 JF - Journal of Optics SN - 2040-8978 TI - General analytic theory of classical collinear three-wave mixing in a monolithic cavity ER - TY - JOUR AU - De, Syamsundar AU - Gil López, Jano AU - Brecht, Benjamin AU - Silberhorn, Christine AU - Sánchez-Soto, Luis L. AU - Hradil, Zdeněk AU - Řeháček, Jaroslav ID - 29524 IS - 3 JF - Physical Review Research KW - General Engineering SN - 2643-1564 TI - Effects of coherence on temporal resolution VL - 3 ER - TY - JOUR AU - Ansari, Vahid AU - Brecht, Benjamin AU - Gil-Lopez, Jano AU - Donohue, John M. AU - Řeháček, Jaroslav AU - Hradil, Zdeněk AU - Sánchez-Soto, Luis L. AU - Silberhorn, Christine ID - 21020 JF - PRX Quantum SN - 2691-3399 TI - Achieving the Ultimate Quantum Timing Resolution VL - 2 ER - TY - JOUR AU - Roman-Rodriguez, V AU - Brecht, Benjamin AU - Srinivasan, K AU - Silberhorn, Christine AU - Treps, N AU - Diamanti, E AU - Parigi, V ID - 22259 JF - New Journal of Physics SN - 1367-2630 TI - Continuous variable multimode quantum states via symmetric group velocity matching VL - 23 ER - TY - GEN AU - Padberg, Laura AU - Eigner, Christof AU - Santandrea, Matteo AU - Silberhorn, Christine ID - 38135 TI - Production of waveguides made of materials from the KTP family ER - TY - CONF AB - We present a frequency multimode integrated SU (1,1) interferometer with a polarization converter and strong signal-idler photon correlations. Phase sensitivity below the shot noise limit is demonstrated, various filtering and seeding strategies are discussed. AU - Ferreri, A. AU - Santandrea, Matteo AU - Stefszky, Michael AU - Luo, Kai Hong AU - Herrmann, Harald AU - Silberhorn, Christine AU - Sharapova, Polina ID - 40374 T2 - Conference on Lasers and Electro-Optics TI - Multimode integrated SU(1,1) interferometer ER - TY - JOUR AU - Pelucchi, Emanuele AU - Fagas, Giorgos AU - Aharonovich, Igor AU - Englund, Dirk AU - Figueroa, Eden AU - Gong, Qihuang AU - Hannes, Hübel AU - Liu, Jin AU - Lu, Chao-Yang AU - Matsuda, Nobuyuki AU - Pan, Jian-Wei AU - Schreck, Florian AU - Sciarrino, Fabio AU - Silberhorn, Christine AU - Wang, Jianwei AU - Jöns, Klaus ID - 37936 IS - 3 JF - Nature Reviews Physics KW - General Physics and Astronomy SN - 2522-5820 TI - The potential and global outlook of integrated photonics for quantum technologies VL - 4 ER -