We present an efficient way of heralding photonic qubit signals using linear optics devices. First we show that one can obtain asymptotically perfect heralding and unit success probability with growing resources. Second, we show that even using finite resources, we can improve qualitatively and quantitatively over earlier heralding results. In the latte r scenario, we can obtain perfect heralded photonic qubits while maintaining a finite success probability. We demonstrate the advantage of our heralding scheme by predicting key rates for device independent quantum key distribution, taking imperfections of sources and detectors into account.
Entanglement is a unique property of quantum systems and an essential resource for many quantum technologies. The ability to transfer or swap entanglement between systems is an important protocol in quantum information science. Entanglement between photons forms the basis of distributed quantum networks and the demonstration of photonic entanglement swapping is essential for their realization. Here an experiment demonstrating entanglement swapping from two independent multimode time-frequency entangled sources is presented, resulting in multiple heralded temporal-mode Bell states. Entanglement…
Multi-photon interference is central to photonic quantum information processing and quantum simulation, usually requiring multiple sources of non-classical light followed by a unitary transformation on their modes. Here, we observe interference in the four-photon events generated by a single silicon waveguide, where the different modes are six frequency channels. Rather than requiring a unitary transformation, the frequency correlations of the source are configured such that photons are generated in superposition states across multiple channels, and interference effects can be seen without fur…
Integrated photonics is a powerful contender in the race for a fault-tolerant quantum computer, claiming to be a platform capable of scaling to the necessary number of qubits. This necessitates the use of high-quality quantum states, which we create here using an all-around high-performing photon source on an integrated photonics platform. We use a photonic molecule architecture and broadband directional couplers to protect against fabrication tolerances and ensure reliable operation. As a result, we simultaneously measure a spectral purity of $99.1 \pm 0.1$ %, a pair generation rate of $4.4 \…
Efficient, high rate photon sources with high single photon purity are essential ingredients for quantum technologies. Single photon sources based on solid state emitters such as quantum dots are very advantageous for integrated photonic circuits, but they can suffer from a high two-photon emission probability, which in cases of non-cryogenic environment cannot be spectrally filtered. Here we propose two temporal purification-by-heralding methods for using a two photon emission process to yield highly pure and efficient single photon emission, bypassing the inherent problem of spectrally overl…
MESA+ Institute for Nanotechnology, University of Twente（特温特大学 MESA+ 纳米技术研究所）；Department of Applied Physics and Science Education, Eindhoven University of Technology（埃因霍温理工大学应用物理与科学教育部）；Department of Electrical Engineering, Eindhoven University of Technology（埃因霍温理工大学电气工程系）
The outstanding progress in nanostructure fabrication and cooling technologies allows what was unthinkable a few decades ago: bringing single-mode mechanical vibrations to the quantum regime. The coupling between photon and phonon excitations is a natural source of nonclassical states of light and mechanical vibrations, and its study within the field of cavity optomechanics is developing lightning-fast. Photonic crystal cavities are highly integrable architectures that have demonstrated the strongest optomechanical coupling to date, and should therefore play a central role for such hybrid quan…
Advanced photonic quantum technology relies on multi-photon interference which requires bright sources of high-purity single photons. Here, we implement a novel domain-engineering technique for tailoring the nonlinearity of a parametric down-conversion crystal. We create pairs of independently-heralded telecom-wavelength photons and achieve high heralding, brightness and spectral purities without filtering.
We propose an optical scheme to generate a superposition of coherent states with enhanced size adopting an interferometric setting at the single-photon level currently available in the laboratory. Our scheme employs a nondegenerate optical parametric amplifier together with two beam splitters so that the detection of single photons at the output conditionally implements the desired superposition of second-order photonic operations. We analyze our proposed scheme by considering realistic on-off photodetectors with nonideal efficiency in heralding the success of conditional events. A high-qualit…
Hyperentanglement of photonic light modes is a valuable resource in quantum information processing and quantum communication. Here we propose a new protocol using the interference of two optical nonlinearities and control of the heralding (detection) basis in the orbital-angular-momentum degree of freedom. This setup is capable of generating states which are both maximally- and hyper- entangled in at least four dimensions. The resultant state in the four-dimensional case is a generalization of the so-called N00N state (a maximally path-entangled state well known in quantum optics). The product…
Device-independent quantum key distribution protocols allow two honest users to establish a secret key with minimal levels of trust on the provider, as security is proven without any assumption on the inner working of the devices used for the distribution. Unfortunately, the implementation of these protocols is challenging, as it requires the observation of a large Bell-inequality violation between the two distant users. Here, we introduce novel photonic protocols for device-independent quantum key distribution exploiting single-photon sources and heralding-type architectures. The heralding pr…
We develop a unified theoretical framework for the efficient description of multiphoton states generated and propagating in loop-based optical networks which contain nonlinear elements. These active optical components are modeled as nonlinear media, resembling a two-mode squeezer. First, such nonlinear components can be seeded to manipulate quantum states of light, as such enabling photon addition protocols. And, second, they can function as an amplifying medium for quantum light. To prove the practical importance of our approach, the impact of multiple round trips is analyzed for states propa…
The nonlinear component of the optomechanical interaction between light and mechanical vibration promises many exciting classical and quantum mechanical applications, but is generally weak. Here we demonstrate enhancement of nonlinear optomechanical measurement of mechanical motion by using pairs of coupled optical and mechanical modes in a photonic crystal device. In the same device we show linear optomechanical measurement with a strongly reduced input power and reveal how both enhancements are related. Our design exploits anisotropic mechanical elasticity to create strong coupling between m…
While integrated photonics is a robust platform for quantum information processing, architectures for photonic quantum computing place stringent demands on high quality information carriers. Sources of single photons that are highly indistinguishable and pure, that are either near-deterministic or heralded with high efficiency, and that are suitable for mass-manufacture, have been elusive. Here, we demonstrate on-chip photon sources that simultaneously meet each of these requirements. Our photon sources are fabricated in silicon using mature processes, and exploit a novel dual-mode pump-delaye…
Error-detection and correction are necessary prerequisites for any scalable quantum computing architecture. Given the inevitability of unwanted physical noise in quantum systems and the propensity for errors to spread as computations proceed, computational outcomes can become substantially corrupted. This observation applies regardless of the choice of physical implementation. In the context of photonic quantum information processing, there has recently been much interest in passive linear optics quantum computing, which includes boson-sampling, as this model eliminates the highly-challenging …
Photonic qubits constitute a leading platform to disruptive quantum technologies due to their unique low-noise properties. The cost of the photonic approach is the non-deterministic nature of many of the processes, including single-photon generation, which arises from parametric sources and negligible interaction between photons. Active temporal multiplexing - repeating a generation process in time and rerouting to single modes using an optical switching network - is a promising approach to overcome this challenge and will likely be essential for large-scale applications with greatly reduced r…
Quantum logic gates for photonic qubits can be implemented using the quantum Zeno effect based on strong two-photon absorption. The fidelity of quantum Zeno gates of this kind may be substantially reduced by photon loss. Heralding on those outcomes in which both of the logical qubits emerge from the Zeno gate can increase the fidelity at the expense of a limited success rate (P.M. Leung et al., Phys. Rev. A 74, 062325 (2006)). We analyze the performance of heralded quantum Zeno gates by solving Schrodinger's equation for a system of photons coupled to three-level atoms. This approach identifie…
Deterministic sources of high-fidelity entangled qubit pairs encoded in the dual-rail photonic basis, i.e., presence of a single photon in one of two orthogonal modes, are a key enabling technology of many applications of quantum information processing, including high-rate high-fidelity quantum communications over long distances. The most popular and mature sources of such photonic entanglement, e.g., those that leverage spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing (sFWM), generate an entangled (so-called, continuous-variable) quantum state that contains contri…
Quantum light source with lithium tantalate for scalable photonic quantum circuits
Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China（电子科技大学基础与前沿研究院）；Center for Quantum Internet, Tianfu Jiangxi Laboratory（天府江西实验室量子互联网中心）；Key Laboratory of Quantum Physics and Photonic Quantum Information, Ministry of Education, University of Electronic Science and Technology of China（电子科技大学量子物理与光子量子信息教育部重点实验室）；State Key Laboratory of Materials for Integrated Circuits, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences（中国科学院上海微系统信息技术研究所集成电路材料国家重点实验室）；Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences（中国科学院大学物质科学和光电子工程中心）
A key obstacle to the experimental realization of many photonic quantum-enhanced technologies is the lack of low-loss sources of single photons in pure quantum states. We demonstrate a promising solution: generation of heralded single photons in a silica photonic chip by spontaneous four-wave mixing. A heralding efficiency of 40%, corresponding to a preparation efficiency of 80% accounting for detector performance, is achieved due to efficient coupling of the low-loss source to optical fibers. A single photon purity of 0.86 is measured from the source number statistics without filtering, and c…
Improving the Loss Tolerance of Heralded Photonic GHZ States for Long-Distance Device-Independent Conference Key Agreement
Imperial College London（帝国理工学院）；Keio University（庆应义塾大学）；Curtin University（科廷大学）；University of Oxford（牛津大学）；National Institute of Information and Communications Technology (NICT)（信息通信研究机构）
Rapid Gaussian Boson Sampling Circuit Screening for GKP States Creation via a Two-Stage Machine Learning Surrogate
Shahid Beheshti University（沙希德·贝赫什提大学）；AriaQuanta Quantum Computing Center（阿里安塔量子计算中心）；Quantum Research Center, Shahid Sattari University of Aeronautical Sciences and Technology（沙希德·萨塔里航空航天科技大学量子研究中心）
Building a quantum repeater network for long distance quantum communication requires photons and quantum registers that comprise qubits for interaction with light, good memory capabilities and processing qubits for storage and manipulation of photons. Here we demonstrate a key step, the coherent transfer of a photon in a single solid-state nuclear spin qubit with an average fidelity of 98% and storage over 10 seconds. The storage process is achieved by coherently transferring a photon to an entangled electron-nuclear spin state of a nitrogen vacancy centre in diamond, confirmed by heralding th…
The faithful storage of a quantum bit of light is essential for long-distance quantum communication, quantum networking and distributed quantum computing. The required optical quantum memory must, first, be able to receive and recreate the photonic qubit and, second, store an unknown quantum state of light better than any classical device. These two requirements have so far been met only by ensembles of material particles storing the information in collective excitations. Recent developments, however, have paved the way for a new approach in which the information exchange happens between singl…
The dark exciton state in semiconductor quantum dots constitutes a long-lived solid-state qubit which has the potential to play an important role in implementations of solid-state based quantum information architectures. In this work, we exploit deterministically fabricated QD microlenses with enhanced photon extraction, to optically prepare and readout the dark exciton spin and observe its coherent precession. The optical access to the dark exciton is provided via spin-blockaded metastable biexciton states acting as heralding state, which are identified deploying polarization-sensitive spectr…
