Abstract Non-Abelian topological charges herald a new epoch in topological classification, featuring multiple tangled-bandgaps that promise conceptual breakthroughs. Here, we engineered the first photonic non-Abelian topological insulators by the integrated waveguide and demonstrating a novel quantum light source that exhibits non-Abelian topological features. We experimentally observed the generation of a discrete-band two-photon source with extended wavelengths of signal and idler photons lying in S and L bands, respectively, exhibiting an enhanced coincidence-to-accidental ratio. Additionally, we demonstrated the robustness of this quantum light sources by introducing significant disorders. Such non-Abelian two-photon source can be engineered within the transmission window of the material as well as provides a natural scheme for optimizing the spectral purity towards robust indistinguishable photons. Our scheme paves the way for non-Abelian topological quantum device applications in quantum light sources engineering, quantum computing and quantum simulation as well as shedding light on interdisciplinary studies of non-Abelian physics and quantum optics.
Abstract Non-Abelian topological charges herald a new epoch in topological classification, featuring multiple tangled-bandgaps that promise conceptual breakthroughs. Here, we engineered the first photonic non-Abelian topological insulators by the integrated waveguide and demonstrating a novel quantum light source that exhibits non-Abelian topological features. We experimentally observed the generation of a discrete-band two-photon source with extended wavelengths of signal and idler photons lying in S and L bands, respectively, exhibiting an enhanced coincidence-to-accidental ratio. Additionally, we demonstrated the robustness of this quantum light sources by introducing significant disorders. Such non-Abelian two-photon source can be engineered within the transmission window of the material as well as provides a natural scheme for optimizing the spectral purity towards robust indistinguishable photons. Our scheme paves the way for non-Abelian topological quantum device applications in quantum light sources engineering, quantum computing and quantum simulation as well as shedding light on interdisciplinary studies of non-Abelian physics and quantum optics.
This paper explores the novel interplay between topological nodal lines in photonic and matter systems and their potential for engineering tailored light-matter entanglement. Topological nodal lines, characterized by closed loops of band degeneracies in momentum space, offer a robust platform for manipulating quantum states due to their inherent protection against local perturbations. We propose and investigate theoretical frameworks for realizing such topological features in systems amenable to strong light-matter coupling, including photonic crystal structures and superconducting circuits coupled to artificial atoms. By harnessing the unique dispersion properties and Berry phases associated with nodal lines, we demonstrate how specific entanglement protocols can be optimized, enabling deterministic generation of entangled photons, robust entanglement transfer, and the creation of highly non-classical states. Our methodology involves detailed analysis of band structures, topological invariants, and light-matter interaction Hamiltonians, coupled with numerical simulations to predict the entanglement fidelity and robustness. The findings suggest that topological nodal lines provide an unprecedented degree of control over the spatial and spectral properties of entangled light and matter states, paving the way for advanced quantum technologies such as fault-tolerant quantum computing, quantum communication, and quantum sensing with enhanced capabilities. This work highlights a promising avenue for integrating condensed matter topology with quantum optics, forging new pathways for fundamental research and practical applications.
Abstract Entanglement, a fundamental concept in quantum mechanics, plays a crucial role as a valuable resource in quantum technologies. The practical implementation of entangled photon sources encounters obstacles arising from imperfections and defects inherent in physical systems and microchips, resulting in a loss or degradation of entanglement. The topological photonic insulators, however, have emerged as promising candidates, demonstrating an exceptional capability to resist defect-induced scattering, thus enabling the development of robust entangled sources. Despite their inherent advantages, building bright and programmable topologically protected entangled sources remains challenging due to intricate device designs and weak material nonlinearity. Here we present an advancement in entanglement generation achieved through a non-magnetic and tunable resonance-based anomalous Floquet insulator, utilizing an optical spontaneous four-wave mixing process. Our experiment demonstrates a substantial enhancement in entangled photon pair generation compared to devices reliant solely on topological edge states and outperforming trivial photonic devices in spectral resilience. This work marks a step forward in the pursuit of defect-robust and bright entangled sources that can open avenues for the exploration of cascaded quantum devices and the engineering of quantum states. Our result could lead to the development of resilient quantum sources with potential applications in quantum technologies.
Engineering and controlling well-defined states of light for quantum information applications is of increasing importance as the complexity of quantum systems grows. For example, in quantum networks, high multi-photon interference visibility requires properly devised pure photon sources. In this paper, we present a theoretical model for a spontaneous parametric down conversion source based on an integrated cavity-waveguide, where single narrow-band, possibly distinct, resonant modes for the idler and the signal fields can be generated. This mode selection takes advantage of the clustering effect, due to the intrinsic dispersion of the nonlinear material. We show that, by engineering the clustering effect in an integrated cavity-waveguide and by using a standard detector, one can efficiently generate heralded pure single photons even with a continuous-wave pumping mode. The photon source proposed in this paper is extremely flexible and could easily be adapted to a wide variety of wavelengths and applications, such as long-distance quantum communication.
There is great interest in designing photonic devices capable of disorder-resistant transport and information processing. In this work we propose to exploit three-dimensional integrated photonic circuits in order to realize two-dimensional discrete-time quantum walks in a background synthetic gauge field. The gauge fields are generated by introducing the appropriate phase shifts between waveguides. Polarization-independent phase shifts lead to an Abelian or magnetic field, a case we describe in detail. We find that, in the disordered case, the magnetic field enhances transport due to the presence of topologically protected chiral edge states that do not localize. Polarization-dependent phase shifts lead to effective non-Abelian gauge fields, which could be adopted to realize Rashba-like quantum walks with spin-orbit coupling. Our work introduces a flexible platform for the experimental study of multiparticle quantum walks in the presence of synthetic gauge fields, which paves the way towards topologically robust transport of many-body states of photons.
Phase matching lies at the heart of the classical nonlinear process for frequency conversion and all-optical processing, as well as the spontaneous parametric process for the quantum light sources generation. In this work, we experimentally demonstrate the coupled-mode phase-matching (CMPM) engineered by the two-paralleled-coupled waveguides on a silicon-on-insulator (SOI) chip, extending the converted beam and entangled photons to the S band and L band. We measure the spectrum and efficiency of wavelength conversion, which successfully validates the designed CMPM scheme. We further measure the pairs generation rate of the biphoton based on the spontaneous four-wave mixing, which features a narrow bandwidth consistent well with the theoretical simulations. Multiple CMPM conditions can be achieved by exploiting the combinations of even and odd supermodes of the coupled system and tuned by designing a proper coupling gap between the two waveguides. The CMPM can extend the FWM nonlinear process ranging from the O band to the U band and even the midinfrared, enriching the working wavelength to a large extent. In addition, the CMPM features a discrete-band narrow bandwidth, which will greatly enhance the encoding density of frequency and the spectral purity of generated photon. In addition, our methods can be easily extended to a wide range of materials such as silicon nitride, dispensing with the dispersion engineering for phase matching.
Topological insulators are materials that have a gapped bulk energy spectrum but contain protected in-gap states appearing at their surface. These states exhibit remarkable properties such as unidirectional propagation and robustness to noise that offer an opportunity to improve the performance and scalability of quantum technologies. For quantum applications, it is essential that the topological states are indistinguishable. We report high-visibility quantum interference of single-photon topological states in an integrated photonic circuit. Two topological boundary states, initially at opposite edges of a coupled waveguide array, are brought into proximity, where they interfere and undergo a beamsplitter operation. We observe Hong-Ou-Mandel interference with 93.1 ± 2.8% visibility, a hallmark nonclassical effect that is at the heart of linear optics-based quantum computation. Our work shows that it is feasible to generate and control highly indistinguishable single-photon topological states, opening pathways to enhanced photonic quantum technology with topological properties, and to study quantum effects in topological materials.