Random number generators are essential to ensure performance in information technologies, including cryptography, stochastic simulations and massive data processing. The quality of random numbers ultimately determines the security and privacy that can be achieved, while the speed at which they can be generated poses limits to the utilisation of the available resources. In this work we propose and demonstrate a quantum entropy source for random number generation on an indium phosphide photonic integrated circuit made possible by a new design using two-laser interference and heterodyne detection. The resulting device offers high-speed operation with unprecedented security guarantees and reduced form factor. It is also compatible with complementary metal-oxide semiconductor technology, opening the path to its integration in computation and communication electronic cards, which is particularly relevant for the intensive migration of information processing and storage tasks from local premises to cloud data centres.
We demonstrate photonic quantum circuits that operate at the stringent levels that will be required for future quantum information science and technology. These circuits are fabricated from silica-on-silicon waveguides forming directional couplers and interferometers. While our focus is on the operation of quantum circuits, to test this operation required construction of a spectrally tuned photon source to produce near-identical pairs of photons. We show non-classical interference with two photons and a two-photon entangling logic gate that operate with near-unit fidelity. These results are a …
Photonic integrated circuits that are manufactured with mature semiconductor technology hold great promise for realizing scalable quantum technology. Efficient interfaces between quantum emitters and nanophotonic devices are crucial building blocks for such implementations on silicon chips. These interfaces can be realized as nanobeam optical cavities with high quality factors and wavelength-scale mode volumes, thus providing enhanced coupling between nanoscale quantum emitters and nanophotonic circuits. Realizing such resonant structures is particularly challenging for the visible wavelength …
Following the simple observation that the interconnection of a set of quantum optical input-output devices can be specified using structural mode VHSIC Hardware Description Language (VHDL), we demonstrate a computer-aided schematic capture workflow for modeling and simulating multi-component photonic circuits. We describe an algorithm for parsing circuit descriptions to derive quantum equations of motion, illustrate our approach using simple examples based on linear and cavity-nonlinear optical components, and demonstrate a computational approach to hierarchical model reduction.
The importance of integrated quantum photonics in the telecom band resides on the possibility of interfacing with the optical network infrastructure developed for classical communications. In this framework, femtosecond laser written integrated photonic circuits, already assessed for quantum information experiments in the 800 nm wavelength range, have great potentials. In fact these circuits, written in glass, can be perfectly mode-matched at telecom wavelength to the in/out coupling fibers, which is a key requirement for a low-loss processing node in future quantum optical networks. In additi…
Using a technique, analogous to coherent population trapping in an atomic system, we propose schemes to create transverse light propagation violating left-right symmetry in a photonic circuit consisting of three coupled waveguides. The frequency windows for the symmetry breaking of the left-right energy flow span over 80 nm. Our proposed system only uses linear passive optical materials and is easy to integrate on a chip.
We report photonic quantum circuits created using an ultrafast laser processing technique that is rapid, requires no lithographic mask and can be used to create three-dimensional networks of waveguide devices. We have characterized directional couplers--the key functional elements of photonic quantum circuits--and found that they perform as well as lithographically produced waveguide devices. We further demonstrate high-performance interferometers and an important multi-photon quantum interference phenomenon for the first time in integrated optics. This direct-write approach will enable the ra…
Photonic integrated circuits play a central role in current and future applications such as communications, sensing, ranging, and information processing. Photonic quantum computing will also likely require an integrated optics architecture for improved stability, scalability, and performance. Fault-tolerant quantum computing mandates very accurate and robust quantum gates. In this work, we demonstrate high-fidelity directional couplers for single-qubit gates in photonic integrated waveguides, utilizing a novel scheme of detuning-modulated composite segments. Specific designs for reduced sensit…
We demonstrate integrated photonic circuits for quantum devices using sputtered polycrystalline aluminum nitride (AlN) on insulator. The on-chip AlN waveguide directional couplers, which are one of the most important components in quantum photonics, are fabricated and show the output power splitting ratios from 50:50 to 99:1. The polarization beam splitters with an extinction ratio of more than 10 dB are also realized from the AlN directional couplers. Using the fabricated AlN waveguide beam splitters, we observe the Hong-Ou-Mandel interference with a visibility of 91.7 +(-) 5.66 %.
The continual success of superconducting photon-detection technologies in quantum photonics asserts cryogenic-compatible systems as a cornerstone of full quantum photonic integration. Here, we present a way to reversibly fine-tune the optical properties of individual waveguide structures through local changes to their geometry using solidified xenon. Essentially, we remove the need for additional on-chip calibration elements, effectively zeroing the power consumption tied to reconfigurable elements, with virtually no detriment to photonic device performance. We enable passive circuit tuning in…
Photonics offers unique advantages as a substrate for quantum information processing, but imposes fundamental scalability challenges. Nondeterministic schemes impose massive resource overheads, while deterministic schemes require prohibitively many identical quantum emitters to realize sizeable quantum circuits. Here we propose a scalable architecture for a photonic quantum computer which needs minimal quantum resources to implement any quantum circuit: a single coherently controlled atom. Optical switches endow a photonic quantum state with a synthetic time dimension by modulating photon-atom…
Leveraging the quantum information processing ability of superconducting circuits and long-distance distribution ability of optical photons promises the realization of complex and large-scale quantum networks. In such a scheme, a coherent and efficient quantum transducer between superconducting and photonic circuits is critical. However, such quantum transducer is still challenging since the use of intermediate excitations in current schemes introduces extra noise and limits bandwidth. Here we realize direct and coherent transduction between superconducting and photonic circuits based on tripl…
We develop a quantum photonic platform that interconnects a high-quality quantum dot single-photon source and a low-loss photonic integrated circuit made in silicon nitride. The platform is characterized and programmed to demonstrate various multiphoton applications, including bosonic suppression laws and photonic entanglement generation. The results show a promising technological route forward to scale-up photonic quantum hardware.
We demonstrate niobium titanium nitride superconducting nanowires patterned on stoichiometric silicon nitride waveguides for detecting visible and infrared photons. The use of silicon nitride on insulator on silicon substrates allows us to simultaneously realize photonic circuits for visible and infrared light and integrate them with nanowire detectors directly on-chip. By implementing a traveling wave detector geometry in this material platform, we achieve efficient single photon detection for both wavelength regimes. Our detectors are an ideal match for integrated quantum optics as they prov…
A semiclassical simulation approach is presented for studying quantum noise in large-scale photonic circuits incorporating an ideal Kerr nonlinearity. A circuit solver is used to generate matrices defining a set of stochastic differential equations, in which the resonator field variables represent random samplings of the Wigner quasi-probability distributions. Although the semiclassical approach involves making a large-photon-number approximation, tests on one- and two-resonator circuits indicate satisfactory agreement between the semiclassical and full-quantum simulation results in the parame…
Topological photonics has been introduced as a powerful platform for integrated optics, since it can deal with robust light transport, and be further extended to the quantum world. Strikingly, valley-contrasting physics in topological photonic structures contributes to valley-related edge states, their unidirectional coupling, and even valley-dependent wave-division in topological junctions. Here, we design and fabricate nanophotonic topological harpoon-shaped beam splitters (HSBSs) based on $120$-deg-bending interfaces and demonstrate the first on-chip valley-dependent quantum information pro…
We report a compact, scalable, quantum photonic integrated circuit realised by combining multiple, independent InGaAs/GaAs quantum-light-emitting-diodes (QLEDs) with a silicon oxynitride waveguide circuit. Each waveguide joining the circuit can then be excited by a separate, independently electrically contacted QLED. We show that the emission from neighbouring QLEDs can be independently tuned to degeneracy using the Stark Effect and that the resulting photon streams are indistinguishable. This enables on-chip Hong-Ou-Mandel-type interference, as required for many photonic quantum information p…
Quantum photonic integration circuits are a promising approach to scalable quantum processing with photons. Waveguide single-photon-detectors (WSPDs) based on superconducting nanowires have been recently shown to be compatible with single-photon sources for a monolithic integration. While standard WSPDs offer single-photon sensitivity, more complex superconducting nanowire structures can be configured to have photon-number-resolving capability. In this work, we present waveguide photon-number-resolving detectors (WPNRDs) on GaAs/Al0.75Ga0.25As ridge waveguides based on a series connection of n…
The spectacular success of silicon-based photonic integrated circuits (PICs) in the past decade naturally begs the question of whether similar fabrication procedures can be applied to other material platforms with more desirable optical properties. In this work, we demonstrate the individual passive components (grating couplers, waveguides, multi-mode interferometers and ring resonators) necessary for building large scale integrated circuits in suspended gallium arsenide (GaAs). Implementing PICs in suspended GaAs is a viable route towards achieving optimal system performance in areas with str…
Photonic integration is an enabling technology for photonic quantum science, offering greater scalability, stability, and functionality than traditional bulk optics. Here, we describe a scalable, heterogeneous III-V/silicon integration platform to produce Si$_3$N$_4$ photonic circuits incorporating GaAs-based nanophotonic devices containing self-assembled InAs/GaAs quantum dots. We demonstrate pure singlephoton emission from individual quantum dots in GaAs waveguides and cavities - where strong control of spontaneous emission rate is observed - directly launched into Si$_3$N$_4$ waveguides wit…
Loss is inevitable for the optical system due to absorption of materials, scattering caused by the defects and surface roughness. In quantum optical circuits, the loss can not only reduce the intensity of signal, but also affect the performance of quantum operations. In this work, we divide losses into unbalanced linear loss and shared common loss, and provide a detailed analysis on how loss affects the integrated linear optical quantum gates. It is found that the orthogonality of eigenmodes and the unitary phase relation of the coupled waveguide modes are destroyed by the loss. As a result, t…
Centre de Nanosciences et de Nanotechnologies, Université Paris-Saclay, CNRS（巴黎萨克雷大学国家科学研究中心纳米科学和纳米技术研究中心）；Université Côte d’Azur, CNRS, Institut de Physique de Nice (INPHYNI)（蔚蓝海岸大学法国国家科学研究中心尼斯物理研究所）；CEA-LETI-Minatec（法国原子能和替代能源委员会技术、电子与信息技术实验室）
Integrated photonics is a leading platform for quantum technologies including nonclassical state generation \cite{Vergyris:2016-35975:SRP, Solntsev:2014-31007:PRX, Silverstone:2014-104:NPHOT, Solntsev:2016:RPH}, demonstration of quantum computational complexity \cite{Lamitral_NJP2016} and secure quantum communications \cite{Zhang:2014-130501:PRL}. As photonic circuits grow in complexity, full quantum tomography becomes impractical, and therefore an efficient method for their characterization \cite{Lobino:2008-563:SCI, Rahimi-Keshari:2011-13006:NJP} is essential. Here we propose and demonstrate…
Quantum information processing holds great promise for communicating and computing data efficiently. However, scaling current photonic implementation approaches to larger system size remains an outstanding challenge for realizing disruptive quantum technology. Two main ingredients of quantum information processors are quantum interference and single-photon detectors. Here we develop a hybrid superconducting-photonic circuit system to show how these elements can be combined in a scalable fashion on a silicon chip. We demonstrate the suitability of this approach for integrated quantum optics by …
We present a modular design for integrated programmable multimode sources of arbitrary Gaussian states of light. The technique is based on current technologies, in particular recent demonstrations of on-chip photon manipulation and generation of highly squeezed vacuum states in semiconductors. While the design is generic and independent of the choice of integrated platform, we adopt recent experimental results on compound semiconductors as a demonstrative example. Such a device would be valuable as a source for many quantum protocols that range from imaging to communication and information pro…
The development of practical methods for synthesis and verification of complex photonic circuits presents a grand challenge for the nascent field of quantum engineering. Of course, classical electrical engineering provides essential foundations and serves to illustrate the degree of sophistication that can be achieved in automated circuit design. In this paper we explore the utility of term rewriting approaches to the transformation of quantum circuit models, specifically applying rewrite rules for both reduction/verification and robustness analysis of photonic circuits for autonomous quantum …
Trapped ions are promising candidates for nodes of a scalable quantum network due to their long-lived qubit coherence times and high-fidelity single and two-qubit gates. Future quantum networks based on trapped ions will require a scalable way to route photons between different nodes. Photonic integrated circuits from fabrication foundries provide a compact solution to this problem. However, these circuits typically operate at telecommunication wavelengths which are incompatible with the strong dipole emissions of trapped ions. In this work, we demonstrate the routing of single photons from a …
Femtosecond laser writing is a powerful technique that allows rapid and cost-effective fabrication of photonic integrated circuits with unique three-dimensional geometries. In particular, the possibility to reconfigure such devices by thermo-optic phase shifters represents a paramount feature, exploited to produce adaptive and programmable circuits. However, the scalability is strongly limited by the flaws of current thermal phase shifters, which require hundreds of milliwatts to operate and exhibit large thermal crosstalk. In this work, thermally-insulating three-dimensional microstructures a…
Photonic integrated circuits (PICs) are today acknowledged as an effective solution to fulfill the demanding requirements of many practical applications in both classical and quantum optics. Phase shifters integrated in the photonic circuit offer the possibility to dynamically reconfigure its properties in order to fine tune its operation or to produce adaptive circuits, thus greatly extending the quality and the applicability of these devices. In this paper, we provide a thorough discussion of the main problems that one can encounter when using thermal shifters to reconfigure photonic circuit…
We study the impact of experimental imperfections in integrated photonic circuits. We discuss the emergence of a moderate biased error in path encoding, and investigate its correlation with properties of the optical paths. Our analysis connects and deepens previous studies in this direction, revealing potential issues for high-precision tests and optical implementations of machine learning.
Scalable photonic quantum technologies are based on multiple nested interferometers. To realize this architecture, integrated optical structures are needed to ensure stable, controllable, and repeatable operation. Here we show a key proof-of-principle demonstration of an externally-controlled photonic quantum circuit based upon UV-written waveguide technology. In particular, we present non-classical interference of photon pairs in a Mach-Zehnder interferometer constructed with X couplers in an integrated optical circuit with a thermo-optic phase shifter in one of the interferometer arms.
In the past 20 years, impressive progress has been made both experimentally and theoretically in superconducting quantum circuits, which provide a platform for manipulating microwave photons. This emerging field of superconducting quantum microwave circuits has been driven by many new interesting phenomena in microwave photonics and quantum information processing. For instance, the interaction between superconducting quantum circuits and single microwave photons can reach the regimes of strong, ultra-strong, and even deep-strong coupling. Many higher-order effects, unusual and less familiar in…
We consider the design of photonic circuits that make use of Ti:LiNbO$_{3}$ diffused channel waveguides for generating photons with various combinations of modal, spectral, and polarization entanglement. Down-converted photon pairs are generated via spontaneous optical parametric down-conversion (SPDC) in a two-mode waveguide. We study a class of photonic circuits comprising: 1) a nonlinear periodically poled two-mode waveguide structure, 2) a set of single-mode and two-mode waveguide-based couplers arranged in such a way that they suitably separate the three photons comprising the SPDC proces…
The recent progress in integrated quantum optics has set the stage for the development of an integrated platform for quantum information processing with photons, with potential applications in quantum simulation. Among the different material platforms being investigated, direct-bandgap semiconductors and particularly gallium arsenide (GaAs) offer the widest range of functionalities, including single- and entangled-photon generation by radiative recombination, low-loss routing, electro-optic modulation and single-photon detection. This paper reviews the recent progress in the development of the…
We study the dynamics of photonic quantum circuits consisting of nodes coupled by quantum channels. We are interested in the regime where time delay in communication between the nodes is significant. This includes the problem of quantum feedback, where a quantum signal is fed back on a system with a time delay. We develop a matrix product state approach to solve the Quantum Stochastic Schrödinger Equation with time delays, which accounts in an efficient way for the entanglement of nodes with the stream of emitted photons in the waveguide, and thus the non-Markovian character of the dynamics. W…
We demonstrate the design of an integrated conditional quantum teleportation circuit and a readout circuit using a two-dimensional photonic crystal single chip. Fabrication and testing of the proposed quantum circuit can be accomplished with current or near future semiconductor process technology and experimental techniques. The readout part of our device, which has potential for independent use as an atomic interferometer, can also be used on its own or integrated with other compatible optical circuits to achieve atomic state detection. Further improvement of the device in terms of compactnes…
Photonic circuits in which stateful components are coupled via guided electromagnetic fields are natural candidates for native implementation of iterative stochastic algorithms based on propagation of information around a graph. Conversely, such message passing algorithms suggest novel circuit architectures for signal processing and computation that are well matched to nanophotonic device physics. Here we construct and analyze a quantum optical model of a photonic circuit for iterative decoding of a class of low-density parity-check (LDPC) codes called expander codes. Our circuit can be unders…
Lithium Niobate on insulator (LNOI) photonics promises to combine the excellent nonlinear properties of Lithium Niobate with the high complexity achievable by high contrast waveguides. However, to date, fabrication challenges have resulted in high-loss and sidewall-angled waveguides, limiting its applicability. We report LNOI single mode waveguides with ultra low propagation loss of 0.4 dB/cm and sidewall angle of 75°. Our results open the route to a highly efficient photonic platform with applications ranging from high-speed telecommunication to quantum technology.
Extensive literature has shown that finite impulse response (FIR) interferometers can be engineered to be insensitive under variations of different physical parameters, e.g., to ensure flat-top response and/or tolerance to fabrication errors. In this context, I will show how the Bloch sphere representation can be a very powerful design tool providing superior physical insight into the working principle of autocorrective devices like broadband 50:50 splitters or flat-top interleavers, that can be therefore designed through simple analytical formulas. I will eventually review the recent progress…
