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.
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.
Entanglement is a valuable resource in quantum information technologies. The practical implementation of entangled photon sources faces obstacles from imperfections and defects inherent in physical systems, 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 programmable topologically protected entangled sources remains challenging due to complex device designs and weak material nonlinearity. Here, we present a development in entangled photon-pair generation achieved through a nonmagnetic and tunable anomalous Floquet insulator, utilizing an optical spontaneous four-wave-mixing process. We verify the nonclassicality and time-energy entanglement of the photons generated by our topological system. Our experiment demonstrates a substantial enhancement in nonclassical photon-pair generation compared to devices reliant only on topological edge states. Our results could lead to the development of resilient quantum sources with potential applications in quantum technology. Published by the American Physical Society 2024
Current integrated implementations of entangled photonic sources are limited by fabrication imperfections and defects that introduce scattering and loss, degrading entanglement quality. Topological photonic insulators have recently emerged as a promising platform for robust photon transport due to their resilience against defect-induced scattering, enabling disorder-tolerant entangled photon generation. However, realizing bright entangled sources in topological systems remains challenging because of weak material optical nonlinearities. Here, we demonstrate entangled photon-pair generation in a nonmagnetic and wavelength-tunable anomalous Floquet topological insulator using spontaneous four-wave mixing. Time-energy entanglement is verified through photon coincidence measurements.
Abstract Entanglement and topology both portray nature at the fundamental level but in different manners. Entangled states of quantum particles are intrinsically sensitive to environment, whereas topological phases of matters represent natural robustness against environmental perturbations. Harnessing topology physics to protect entanglement thus has a great potential for reliable quantum applications. However, generating topologically-protected entanglement remains a significant challenge, which requires operating complex quantum devices in combined extreme conditions. Here we report topologically-protected quantum entanglement emitters, that emit topological Einstein-Podolsky-Rosen entangled state and topological multiphoton entangled state from a monolithically-integrated plug-and-play silicon-photonic chip in ambient conditions. The device emulating a photonic anomalous Floquet insulator allows the generation of up to four-photon topological entangled states at nontrivial edge modes. More importantly, we show that the Einstein-Podolsky-Rosen entanglement emitters can be topologically protected against artificial structure defects, by comparing tomographically measured fidelities of 0.968 ± 0.004 and 0.951 ± 0.01 for the perfect and defected emitters, respectively. Our topologically-protected entanglement emitters may find applications in photonic quantum computation and quantum simulation, and in the study of quantum topological physics.
Robust Integrable Quantum Optical Sources, Constructed by Topological Boundary States, Are Crucial for the on-chip Quantum Information Processing. However, Limited by the Bulk-edge Correspondence, the Implementation of Topological Boundary Channels Necessitates a Substantial Number of Bulk Sites, Which Notably Diminishes the Ratio of Ring Resonators to Generate Quantum Sources. How to Achieve Topologically-protected Quantum Sources With the Extremely Enhanced Utilization Efficiency of Optical Resonators Remains a Challenge. Here, the First Realization of Hyperbolic Topological Quantum Sources is reported, Which Possess a Dominated Number of Boundary Resonators Than That in the Bulk Domain. Specifically, Hyperbolic Topological Quantum Sources Require Fewer Resources (i.e., the number of ring resonators) to Achieve the Same Level of Brightness Compared With Euclidean Topological Quantum Sources. Furthermore, the Robust Correlated- and Entangled-photon Pairs Are Measured. The Work Possesses Potential Applications in Integrable Quantum Circuits and Suggests a Novel Way on the Exploration of Quantum Physics in Non-Euclidean Space.
The efficient and controllable generation of entangled photon pairs is a cornerstone for advancing quantum technologies, including quantum computing, communication, and sensing. Traditional methods, primarily relying on spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing (SFWM) in bulk nonlinear crystals or waveguides, often suffer from low efficiency, bulky form factors, and limited control over the spectral and spatial properties of the generated photons. This paper explores a transformative approach leveraging resonant Bound States in the Continuum (BICs) within nanophotonic structures to overcome these limitations. BICs are extraordinary optical resonances characterized by theoretically infinite quality (Q) factors, enabling extreme light localization and immense field enhancement within subwavelength volumes. By integrating nonlinear optical materials into BIC-supporting structures, such as photonic crystal slabs or metasurfaces, the local electric field strength experienced by the nonlinear medium can be dramatically increased, boosting the efficiency of entangled photon generation. Furthermore, the sharp, tailor-able spectral response of BICs offers unprecedented control over the joint spectral amplitude of the photon pairs, promising high degrees of spectral purity and entanglement fidelity. This work outlines the theoretical underpinnings, potential device architectures, and anticipated advantages of BIC-enhanced entangled photon sources, paving the way for compact, high-brightness, and spectrally engineered quantum light sources critical for next-generation quantum technologies.
The interplay between topology and quantum entanglement holds profound implications for fundamental physics and the advancement of quantum technologies. Topological phases of matter are characterized by robust properties impervious to local perturbations, while entanglement serves as a critical resource for quantum information processing. Floquet engineering, the manipulation of quantum systems through periodic driving, offers a powerful non-equilibrium pathway to realize novel topological states that may not exist in static systems. This paper explores the theoretical and experimental avenues for realizing topological quantum entanglement within Floquet-engineered lattices. We review the foundational concepts of Floquet topological phases and various measures of entanglement, such as entanglement entropy and entanglement spectrum. We then delve into the methodologies for designing such systems across diverse platforms, including ultracold atoms in optical lattices, photonic waveguide arrays, and superconducting circuits. The discussion highlights how Floquet driving can induce robust entanglement in topological edge and bulk states, paving the way for fault-tolerant quantum information storage and processing. We propose specific protocols for generating and detecting topologically-protected entangled states, considering the challenges associated with heating and decoherence in periodically driven systems. Ultimately, this work emphasizes the potential of Floquet engineering as a versatile tool for synthesizing exotic entangled topological states, fostering new frontiers in quantum science and engineering.