Quantum key distribution requires photon-pair sources with high spectral correlation. Meanwhile, by applying wavelength-division multiplexing, quantum information capacity can be increased massively. This work experimentally achieves an efficient, high-quality multichannel photon-pair source that matches the standard International Telecommunication Union frequency grid. Strong, uniform spectral correlation over multiple channels is demonstrated by reconstructing the joint spectral intensity with high-resolution, probe-swept stimulated four-wave mixing.
Quantum key distribution requires photon-pair sources with high spectral correlation. Meanwhile, by applying wavelength-division multiplexing, quantum information capacity can be increased massively. This work experimentally achieves an efficient, high-quality multichannel photon-pair source that matches the standard International Telecommunication Union frequency grid. Strong, uniform spectral correlation over multiple channels is demonstrated by reconstructing the joint spectral intensity with high-resolution, probe-swept stimulated four-wave mixing.
With the rapid development of quantum information technology, fully connected multi-user quantum entanglement distribution networks have received increasing attention. Among these, multi-wavelength quantum light sources are key devices for establishing connections between multiple users. Despite recent impressive advances, there are still challenges in increasing the wavelength number of photon pairs due to limitations in the design and fabrication of nonlinear optical devices. The potentials of silicon nitride (Si3N4) microring resonators (MRRs), as scalable platforms for multi-wavelength quantum light sources, are explored in this work. The key design parameters of the Si3N4 MRRs, including waveguide dimension, resonator dispersion, and coupling condition, are comprehensively analyzed to optimize photon-pair generation. Based on these parameters, a Si3N4 MRR with a free spectral range of 20 GHz and an average quality factor of 1.6 million is designed and fabricated. This small free spectral range can generate more channels of correlated photon pairs by using the same wavelength resources. The high-quality resonator contributes to the enhancement of the rate of generating high photon pairs , which are critical for quantum entanglement distribution. With a continuous-wave pump laser, correlated photon pairs across a wide spectral range are generated through the spontaneous four-wave mixing (SFWM). The coincidence-to-accidental ratio (CAR) measurements verify the strong quantum correlation between photon pairs, highlighting the reliability of the system for entanglement distribution. Furthermore, the generation and output characteristics of quantum-correlated photon pairs are experimentally investigated with a tunable bandpass filter. The results demonstrate that 71 wavelength-correlated photon pairs within a 25.6 nm spectral range are successively generated as shown in the Fig. A. Our results pave the way for developing the multi-wavelength quantum light sources with Si3N4 platform, thereby advancing the multi-user quantum networks.
We report an efficient energy-time entangled photon-pair source based on four-wave mixing in a CMOS-compatible silicon photonics ring resonator. Thanks to suitable optimization, the source shows a large spectral brightness of 400\,pairs of entangled photons /s/MHz for 500μW pump power. Additionally, the resonator has been engineered so as to generate a frequency comb structure compatible with standard telecom dense wavelength division multiplexers. We demonstrate high-purity energy-time entanglement, i.e., free of photonic noise, with near perfect raw visibilities (>~98\%) between various channel pairs in the telecom C-band. Such a compact source stands as a path towards more complex quantum photonic circuits dedicated to quantum communication systems.
Abstract Scalable quantum networks require high-quality multi-wavelength light sources to enable simultaneous quantum communication among multiple users 1 . However, realizing such sources with high brightness, low noise, and chip-scale integration remains challenging. We demonstrate a high-quality and multi-wavelength quantum light source based on a periodically poled thin-film lithium niobate (TFLN) microring resonator employing spontaneous parametric down-conversion (SPDC) with a 100-GHz free spectral range (FSR), compatible with International Telecommunication Union (ITU) Channel Grid. In our experiment, twelve pairs of non-degenerate photon pairs are generated, exhibiting a photon-pair generation rate (PGR) of 817 MHz/mW, brightness of 1.86 × 10 9 Hz/mW 2 /GHz, and a coincidence-to-accidental ratio (CAR) of 51,829 ± 2204. The source enables predictable single photons with g (2) (0) = 0.015 ± 0.006 and energy-time entanglement with 99.5% raw visibility. Operating at room temperature, telecom wavelengths, and compatible with network channels, this work represents a crucial step toward realistic scalable, integrated quantum photonic networks in the future.
Frequency entangled photon sources are in high demand in a variety of optical quantum technologies, including quantum key distribution, cluster state quantum computation and quantum metrology. In the recent decade, chip-scale entangled photon sources have been developed using silicon platforms, offering robustness, large scalability and CMOS technology compatibility. Here, we report the generation of frequency correlated photon pairs using a 150-GHz silicon nitride ring cavity. First, the device is characterized for studying the phase matching condition during spontaneous four-wave mixing. Next, we evaluate the joint spectrum intensity of the generated photons and confirm the photon pair generation in a total of 42 correlated frequency mode pairs, corresponding to a bandwidth of 51.25 nm. Finally, the experimental results are analyzed and the joint spectral intensity is quantified in terms of the phase matching condition.
Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs.
Photon pair sources with the capability to tune the wavelength and correlation properties of the generated photons can be useful for quantum applications such as communication, sensing, and computing. Silicon devices based on the SOI (silicon-on-insulator) platform benefits from both tight modal confinement, due to high index contrast between core and cladding, and CMOS compatible manufacturing process, making it a suitable platform for such sources. In the present work, we discuss the possibility of using planar resonant silicon devices with bend radii of a few tens of microns as photon pair sources. We discuss that a silicon nanophotonic chip consisting of either a single microring or coupled microrings can be used to generate photon pairs around 1.55 um. We discuss that the photons are generated in multiple pairs of wavelengths and can be tuned over several nanometers, demonstrating the capability to generate wavelength division multiplexed photon pairs at freely chosen telecommunication-band wavelengths. Further on, we discuss the ease of control over the bi-photon spectrum of the generated photon pairs and its implication in controlling their correlation properties. Uncorrelated photon pairs can be used to herald a single photon, and correlated photon pairs can be used in various quantum applications such as communication and sensing. In the end, we discuss the design parameters of a single microring resonator based sources.