Abstract The lithium niobate on insulator (LNOI) platform has revolutionized lithium niobate materials, and a series of quantum photonic chips have exhibited unprecedented performances. Quantum frequency conversion (QFC) that enables quantum state preservation during frequency conversion is crucial in quantum technology. This work demonstrates a low-noise QFC process on the LNOI nanophotonic platform, connecting telecom and near-visible bands. An internal conversion efficiency of 73% and an on-chip noise count of 900 counts per second (cps) are achieved. Furthermore, the preservation of quantum statistical properties is verified, indicating the QFC chip’s promise for extensive applications of LNOI integrated circuits in quantum information. Based on this chip, we constructed an upconversion single-photon detector with a detection efficiency of 8.7% and a noise of 300 cps, paving the way to integrated on-chip single-photon detection. The realization of a low-noise QFC device also provide a pathway for practical chip-scale QFC-based quantum systems in heterogeneous configurations.
Abstract The lithium niobate on insulator (LNOI) platform has revolutionized lithium niobate materials, and a series of quantum photonic chips have exhibited unprecedented performances. Quantum frequency conversion (QFC) that enables quantum state preservation during frequency conversion is crucial in quantum technology. This work demonstrates a low-noise QFC process on the LNOI nanophotonic platform, connecting telecom and near-visible bands. An internal conversion efficiency of 73% and an on-chip noise count of 900 counts per second (cps) are achieved. Furthermore, the preservation of quantum statistical properties is verified, indicating the QFC chip’s promise for extensive applications of LNOI integrated circuits in quantum information. Based on this chip, we constructed an upconversion single-photon detector with a detection efficiency of 8.7% and a noise of 300 cps, paving the way to integrated on-chip single-photon detection. The realization of a low-noise QFC device also provide a pathway for practical chip-scale QFC-based quantum systems in heterogeneous configurations.
Quantum frequency conversion (QFC) plays a critical role in practical quantum information technology as it provides a bridge among different quantum devices, which usually operate at different optimal wavelength. Photons with longer wavelength feature lower propagation loss and lower solar radiation noise in free space, hence hold promise for daylight long distance quantum communication. Besides, wavelength over 2 μ m also overlap with the absorption band of many important molecules, hence is of great importance for gases and molecules detection. Yet development of technology in this region has been hindered primarily by the spectral mismatch with other quantum devices, notably quantum detection and memories, which optimally operate in the visible band. Here, we demonstrate the first QFC of 2 μ m photons to the visible region on domain-engineered thin-film lithium niobate (TFLN) platform. Benefiting from the strong nonlinearity in such integrated platform, the highest internal quantum conversion efficiency of 42% is achieved at an exceptionally low pump saturation power of only 58 mW . This work provides an efficient interconnection between photons operating at the visible and 2 μ m bands in the integrated platform, pushing forward the development of practical quantum chips for application of quantum communication, sensing and metrology in the future. • Strong mode confinement and domain-engineered thin film lithium niobate (TFLN), combined with large χ ( 2 ) , enable efficient on-chip nonlinear conversion. • First demonstration of quantum frequency conversion (QFC) of 2 μ m band photon on thin film lithium niobate.
Quantum frequency conversion (QFC) plays a crucial role in constructing seamless interconnection between quantum systems operating at different wavelengths. To advance future quantum technology, chip-scale integrated QFC components, featuring high efficiency, small footprint, low power consumption, and high scalability, are indispensable. In this work, we demonstrate the first hybrid integrated QFC chip on a thin-film lithium niobate platform that connects the telecom and visible bands. Benefiting from the periodically poled microring resonator with ultra-high normalized conversion efficiency of 386,000%/W, an ultra-low pump power of 360 μW is achieved, which is more than two orders of magnitude lower than the traditional straight waveguide scheme. By injecting current into the chip, an on-chip quantum efficiency of 57% and a noise count of ∼7000 counts per second are achieved. Such an electrically pumped, integrated, and scalable QFC chip would significantly advance the integration of quantum networks and the development of chip-scale quantum optical systems.
Lithium-Niobate-On-Insulator (LNOI) is emerging as a promising platform for integrated quantum photonic technologies because of its high second-order nonlinearity and compact waveguide footprint. Importantly, LNOI allows for creating electro-optically reconfigurable circuits, which can be efficiently operated at cryogenic temperature. Their integration with superconducting nanowire single-photon detectors (SNSPDs) paves the way for realizing scalable photonic devices for active manipulation and detection of quantum states of light. Here we demonstrate integration of these two key components in a low loss (0.2 dB/cm) LNOI waveguide network. As an experimental showcase of our technology, we demonstrate the combined operation of an electrically tunable Mach-Zehnder interferometer and two waveguide-integrated SNSPDs at its outputs. We show static reconfigurability of our system with a bias-drift-free operation over a time of 12 hours, as well as high-speed modulation at a frequency up to 1 GHz. Our results provide blueprints for implementing complex quantum photonic devices on the LNOI platform.
Wavelength transduction of single-photon signals is indispensable to networked quantum applications, particularly those incorporating quantum memories. Lithium niobate nanophotonic devices have demonstrated favorable linear, nonlinear, and electro-optical properties to deliver this crucial function while offering superior efficiency, integrability, and scalability. Yet, their quantum noise level—a crucial metric for any single-photon-based application—has yet to be investigated. In this work, we report the first, to the best of our knowledge, study with the focus on telecom to near-visible conversion driven by a small detuned telecom pump for practical considerations in distributed quantum processing over fiber networks. Our results find the noise level to be on the order of 10 − 4 photons per time-frequency mode for high conversion, allowing faithful pulsed operations. Through carefully analyzing the origins of such noise and each’s dependence on the pump power and wavelength detuning, we have also identified a formula for noise suppression to 10 − 5 photons per mode. Our results assert a viable, low-cost, and modular approach to networked quantum processing and beyond using lithium niobate nanophotonics.
In this paper, we demonstrate integrated photonic chips for multichannel quantum frequency conversion (QFC) based on reverse-proton-exchange periodically poled lithium niobate waveguides. The integrated chip is fiber coupled with two 34-channel fiber arrays, showing an average fiber-to-fiber sum-frequency generation (SFG) conversion efficiency of about 60% for multichannels. Then the same integrated chip is used to perform multichannel differential-frequency generation (DFG), showing the potential application in long-distance multimode quantum memory. Moreover, the integrated chip is utilized to construct a multichannel up-conversion detector, which has extensive applications including deep-space laser communication, high-rate quantum-key distribution, and single-photon imaging.
Quantum photonics has advanced rapidly and become a leading approach for developing a broad range of quantum technologies, including quantum communications, quantum information processing, quantum computing, and quantum sensing. Besides, the emerging photonic integrated circuits (PIC) technology has been widely used to implement versatile optical elements advantageous for different quantum applications. For example, PIC-based devices have functioned as building blocks, such as photonic qubit sources, linear optical circuits, modulators, and even single-photon detectors, for realizing highly integrated, large-scale quantum computing schemes. In such a powerful quantum photonic integrated circuits (QPIC) scheme, the creation, manipulation, and testing of quantum entanglement states from the generated qubits via a reconfigurable photonic circuitry are essential. Though the state-of-the-art PIC technology is established based on Si photonics due to its widely mature nanophotonic circuit (waveguide) fabrication technology supported by the existing immense semiconductor industry, Si-based PIC has limitations in implementing efficient and fast active elements that usually demand a quadratic nonlinearity. Lithium niobate (LN), renowned as “the silicon of photonics”, has long been a popular material widely used in integrated-optical and nonlinear-optical applications. A great variety of passive and active photonic elements have been realized in the LN platform. Recently, a novel material based on high-quality single-crystalline films of LN, known as thin-film LN on insulator (LNOI), has been developed and has soon drawn enormous attention for its greatly promising ability to realize nanoscale PIC/QPIC in this iconic optical material platform. In this presentation, we report our recent studies on several key LN PIC building blocks for developing novel quantum photonic sources and circuits, including highly integrated photonic-circuit periodically poled lithium niobate (PPLN) chips for photon-pair generation and manipulation, for high-dimensional frequency-entangled qudit production, for time-frequency grid-state generation, for continuous-variable squeezed vacuum state generation, and their potential applications to quantum computing/communication/sensing technology. Besides, a PP-LNOI electro-optic (EO) polarization mode converter (PMC) useful for demonstrating fast control of quantum polarization states and other LNOI circuit elements as QPIC building blocks will also be presented.