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Programmable lithium niobate photonic chip for near-ideal path entanglement and frequency entanglement

Ping Xu, Jia-Chen Duan, Yu Sun, Changwei Sun, Yan-Xiao Gong, Shining N. Zhu

Published Mar 18, 2025• 0 citations
Publisher

Abstract

Abstract Quantum photonic chip is a powerful platform to prepare multi-functional quantum light sources and actualize complex quantum information processing for its advantages of integration, stability, mass production, and reconfigurability. In this work, we design and fabricate a lithium niobate quantum photonic chip, consisting of tandem multi-poling structures, Mach-Zehnder interferometers, and electro-optic modulation, to produce multiple near-ideal quantum light sources including anti-bunching, path and frequency entangled photon pairs. The anti-bunching photon pairs exhibit off-chip Hong-Ou-Mandel interference visibilities above 99%. The fidelities of both frequency and path entanglement exceed 0.99. Meanwhile, all the quantum states hold a wide wavelength tuning range and high coupling efficiency from the chip. Our work paves the way for the development of programmable multi-functional quantum light sources and further promoting various quantum information tasks and enriching the architectures of on-chip quantum information processing.

DOI
10.21203/rs.3.rs-6019580/v1

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Abstract Quantum photonic chip is a powerful platform to prepare multi-functional quantum light sources and actualize complex quantum information processing for its advantages of integration, stability, mass production, and reconfigurability. In this work, we design and fabricate a lithium niobate quantum photonic chip, consisting of tandem multi-poling structures, Mach-Zehnder interferometers, and electro-optic modulation, to produce multiple near-ideal quantum light sources including anti-bunching, path and frequency entangled photon pairs. The anti-bunching photon pairs exhibit off-chip Hong-Ou-Mandel interference visibilities above 99%. The fidelities of both frequency and path entanglement exceed 0.99. Meanwhile, all the quantum states hold a wide wavelength tuning range and high coupling efficiency from the chip. Our work paves the way for the development of programmable multi-functional quantum light sources and further promoting various quantum information tasks and enriching the architectures of on-chip quantum information processing.
ABSTRACT The quantum photonic chip is a powerful platform to prepare multi‐functional quantum light sources and actualize complex quantum information processing for its advantages of integration, stability, mass production, and reconfigurability. In this work, we design and fabricate a lithium niobate quantum photonic chip, consisting of tandem multi‐poling structures, Mach–Zehnder interferometers, and electro–optic modulators. By programming these components, we produce multiple wavelength–tunable high‐fidelity quantum light sources, including anti‐bunching, path, and frequency entangled photon pairs. The anti‐bunching photon pairs exhibit off‐chip Hong–Ou–Mandel interference visibilities above 99%. The fidelities of both frequency and path entanglement exceed 0.99. Meanwhile, all the quantum states maintain high coupling efficiency from the chip. Our work paves the way for the development of programmable multi‐functional quantum light sources and fiber‐based quantum sensing and quantum communication networks that are sensitive to the useful brightness and quality of quantum light sources.
Integrated quantum optics becomes a consequent tendency towards practical quantum information processing. Here, we report the on-chip generation and manipulation of photonic entanglement based on reconfigurable lithium niobate waveguide circuits. By introducing periodically poled structure into the waveguide interferometer, two individual photon-pair sources with controllable phase-shift are produced and cascaded by a quantum interference, resulting in a deterministically separated identical photon pair. The state is characterized by 92.9% visibility Hong-Ou-Mandel interference. Continuous morphing from two-photon separated state to bunched state is further demonstrated by on-chip control of electro-optic phase-shift. The photon flux reaches ~1.4*10^7 pairs nm-1 mW-1. Our work presents a scenario for on-chip engineering of different photon sources and paves a way to the fully integrated quantum technologies.
A consequent tendency toward high-performance quantum information processing is to develop the fully integrated photonic chip. Here, we report the on-chip generation and manipulation of entangled photons based on reconfigurable lithium-niobate waveguide circuits. By introducing a periodically poled structure into the waveguide circuits, two individual photon-pair sources with a controllable electro-optic phase shift are produced within a Hong-Ou-Mandel interferometer, resulting in a deterministically separated identical photon pair. The state is characterized by 92.9±0.9% visibility Hong-Ou-Mandel interference. The photon flux reaches ∼1.4×10(7) pairs nm-1 mW-1. The whole chip is designed to contain nine similar units to produce identical photon pairs spanning the telecom C and L band by the flexible engineering of nonlinearity. Our work presents a scenario for on-chip engineering of different photon sources and paves the way to fully integrated quantum technologies.
Generating and interfering nonclassical states of light is fundamental to optical quantum information science and technology. Quantum photonic integrated circuits provide one pathway towards scalability by combining nonlinear sources of nonclassical light and programmable circuits in centimeter-scale devices. The key requirements for quantum applications include efficient generation of indistinguishable photon-pairs and high-visibility programmable quantum interference. Here, we demonstrate a lithium niobate-on-insulator (LNOI) integrated photonic circuit that generates a two-photon path-entangled state, and a programmable interferometer for quantum interference. We generate entangled photons with ∼2.3×10^{8} pairs/s/mW brightness and perform quantum interference experiments on the chip with 96.8±3.6% visibility. LNOI is an emerging photonics technology that has revolutionized high-speed modulators and efficient frequency conversion. Our results provide a path towards large-scale integrated quantum photonics including efficient photon-pair generation and programmable circuits for applications such as boson sampling and quantum communications.
Integrated quantum photonic technologies require scalable devices with high-visibility quantum interference. Recent studies have demonstrated that lithium niobate on insulator enables efficient nonlinear interactions, via quasi-phase matching in periodically poled lithium niobate (PPLN) waveguides. However, the on-chip control of two-photon interference utilizing path entanglement remains limited. In this study, we demonstrate on-chip generation of single-photon sources via quantum interference using path-entangled N00N states in two ways. Using the basic structure of a reverse Hong–Ou–Mandel (RHOM) configuration, we directly observe high on-chip visibility of quantum interference. We achieve a visibility of 97.7% ± 1.1% using a dual-PPLN waveguide as the basic RHOM configuration. To improve the compactness, efficiency, and stability of on-chip operation, we further incorporate a PPLN ring resonator with a Sagnac loop. This allows counter-propagating paths to share a single periodically poled waveguide, achieving a visibility of 84.4% ± 1.6%. These results demonstrate that lithium niobate on insulator (LNOI)-based quantum photonic systems provide a robust foundation for the development of future integrated quantum technologies.
Quantum technologies have surpassed classical systems by leveraging the unique properties of superposition and entanglement in photons and matter. Recent advancements in integrated quantum photonics, especially in silicon-based and lithium niobate platforms, are pushing the technology toward greater scalability and functionality. Silicon circuits have progressed from centimeter-scale, dual-photon systems to millimeter-scale, high-density devices that integrate thousands of components, enabling sophisticated programmable manipulation of multi-photon states. Meanwhile, lithium niobate, thanks to its wide optical transmission window, outstanding nonlinear and electro-optic coefficients, and chemical stability, has emerged as an optimal substrate for fully integrated photonic quantum chips. Devices made from this material exhibit high efficiency in in generating, manipulating, converting, storing, and detecting photon states, thereby establishing a basis for deterministic multi-photon generation and single-photon quantum interactions, as well as comprehensive frequency-state control. This review explores the development of integrated photonic quantum technologies based on both silicon and lithium niobate, highlighting invaluable insights gained from silicon-based systems that can assist the scaling of lithium niobate technologies. It examines the functional integration mechanisms of lithium niobate in electro-optic tuning and nonlinear energy conversion, showcasing its transformative impact throughout the photonic quantum computing process. Looking ahead, we speculate on the developmental pathways for lithium niobate platforms and their potential to revolutionize areas such as quantum communication, complex system simulation, quantum sampling, and optical quantum computing paradigms.