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Reconfigurable Photonic Computing and Heterogeneous Architectures for AI and RF Defense Systems

A theoretical model of low power microring for dual-pump squeezing-enabled photonics

Tongyao Wu, Qian Cai, Benjamin Hayden, Elham Heidari

Published Jun 9, 2026• 0 citations
Publisher

Abstract

Squeezed light is an essential nonclassical resource for quantum sensing, continuous-variable quantum information processing, low-noise optical communication, and new photonic computing systems. However, to make practical use of it, we need compact, low-power squeezed-light sources that can fit on a chip. In this work, we introduce a theoretical model of a dual-pump microring optical parametric amplifier for squeezed-light integrated photonics. The model outlines cavity-enhanced Kerr four-wave mixing among two pump fields, a signal mode, and the conjugate idler sideband. We use a linearized quantum Langevin approach under the undepleted-pump assumption. We derive the frequency-domain inputoutput relation and assess the output quadrature noise based on several factors: external coupling rate, intrinsic loss, pump power, signal detuning, nonlinear coefficient, and dispersion. First, we analyze a dispersion-engineered silicon nitride microring that operates in the telecom band. It shows that moderate external coupling offers the best trade-off between intracavity field enhancement and squeezed-field extraction. With the right pump detuning, the simulated silicon nitride resonator achieves over 10 dB of quadrature noise reduction at milliwatt-level input pump powers. We also compare AlGaAs and InP microring platforms, demonstrating that the squeezing performance is influenced not only by the nonlinear coefficient but also by the combined effects of material nonlinearity, cavity quality factor, loss, coupling, dispersion, and detuning. This framework gives design guidelines for low-power, chip-scale squeezed-light sources aimed at future quantum and AI-oriented photonic integrated circuits.

DOI
10.1117/12.3101335

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Squeezed light is an essential nonclassical resource for quantum sensing, continuous-variable quantum information processing, low-noise optical communication, and new photonic computing systems. However, to make practical use of it, we need compact, low-power squeezed-light sources that can fit on a chip. In this work, we introduce a theoretical model of a dual-pump microring optical parametric amplifier for squeezed-light integrated photonics. The model outlines cavity-enhanced Kerr four-wave mixing among two pump fields, a signal mode, and the conjugate idler sideband. We use a linearized quantum Langevin approach under the undepleted-pump assumption. We derive the frequency-domain inputoutput relation and assess the output quadrature noise based on several factors: external coupling rate, intrinsic loss, pump power, signal detuning, nonlinear coefficient, and dispersion. First, we analyze a dispersion-engineered silicon nitride microring that operates in the telecom band. It shows that moderate external coupling offers the best trade-off between intracavity field enhancement and squeezed-field extraction. With the right pump detuning, the simulated silicon nitride resonator achieves over 10 dB of quadrature noise reduction at milliwatt-level input pump powers. We also compare AlGaAs and InP microring platforms, demonstrating that the squeezing performance is influenced not only by the nonlinear coefficient but also by the combined effects of material nonlinearity, cavity quality factor, loss, coupling, dispersion, and detuning. This framework gives design guidelines for low-power, chip-scale squeezed-light sources aimed at future quantum and AI-oriented photonic integrated circuits.
Squeezed light constitutes a key resource for quantum optical technologies including quantum sensing, computing, communication and metrology. For many applications the generation of squeezed light typically requires at least two nonlinear optical stages involving careful phase and frequency matching to achieve the required mixing of squeezed and coherent light. In our work, we introduce an on-chip system that simplifies the generation of coherent-squeezed light, utilizing only a single squeezing stage. We achieve this by pumping a silicon nitride (Si3N4\mathrm{Si_3N_4}Si3​N4​) microring resonator to produce single-mode squeezed light through four-wave mixing at the same frequency as the pump mode, leveraging the inherent χ(3)χ^{(3)}χ(3)-nonlinearity of the Si3N4\mathrm{Si_3N_4}Si3​N4​ resonator. Our on-chip system demonstrates a squeezing of -4.7 dB with a clear perspective towards -10 dB squeezing. We also provide a theoretical model that describes the straightforward yet robust generation of single-mode squeezing at the injection locking point of the ring resonator. In fact, we show that a design with a normal dispersion can be used for robust generation of bright squeezed light without the need for careful suppression of unwanted nonlinear processes. Overall, our findings highlight an approach which drastically simplifies the generation of coherent-squeezed light in photonic integrated circuits.
Using a general Hamiltonian treatment, we theoretically study the generation of degenerate quadrature squeezing in a dual-pumped integrated microring resonator coupled to a waveguide. Considering a dual-pump four-wave mixing configuration in an integrated Si3N4{\text{Si}}_{3}{\text{N}}_{4}Si3​N4​ platform, and following the coupled-mode theory approach, we investigate the effects of parasitic quantum nonlinear optical processes on the generation of squeezed light. Considering five resonance modes in this approach allows us to include the most important four-wave mixing processes involved in such a configuration. We theoretically explore the effects of the pump detunings on different nonlinear processes and show that the effects of some of the parasitic processes are effectively neutralized by symmetrically detuning the two pumps. This yields a significant enhancement in the output squeezing quality without physically changing the structure, but suffers from the trade-off of requiring substantially higher pump power for a fixed target level of squeezing.
Squeezed states, with their noise reduction below the standard quantum limit, are promising quantum states of light exploited for enhancing sensitivity in quantum sensing or as carriers of information in continuous variable quantum computing and communication. To make use of their quantum advantage, the main common challenge in generating these states is achieving high levels of squeezing in low loss setups.Over the years, several bulk optical nonlinear crystals and cavities have been employed for the generation of different types of high-quality squeezed states. However, recent progress in fabricating ultra-low loss integrated waveguides has shifted the interest of the community towards the integration of squeezing sources to gain advantages in terms of compactness, scalability, and reproducibility.The aim of this thesis is to investigate the main characteristics, limits, and requirements for the generation of vacuum and bright squeezed states by second- and third-order nonlinear devices, with more emphasis on integrated cavities. In particular, we demonstrate high on-chip intensity difference squeezing between bright mode pairs created in an engineered SiN microring resonator. In addition, we propose the use of the Ikeda map, a semi-classical simulation tool, for the investigation of two-mode quadrature squeezing generation in microresonators, discussing its competitiveness against standard quantum models. These results contribute to the optimization of engineered integrated devices with the aim of attaining high levels of squeezing sufficient to bring real advantages in classical and quantum applications.
Macroscopic bright squeezed light is a crucial continuous-variable quantum resource. However, generating it in integrated Kerr microresonators typically requires strong external overcoupling, which inevitably increases the parametric oscillation threshold and forces a reliance on noisy pump amplifiers. Here, we demonstrate a foundry-compatible silicon nitride ( Si 3 N 4 ) optical parametric oscillator (OPO) that successfully breaks this fundamental trade-off. By leveraging ultralow intrinsic loss alongside a large-free-spectral-range microresonator and a broadband pulley coupler, we achieve a milliwatt-level oscillation threshold with high escape efficiencies across dual telecom bands (C and L). This architecture enables the robust, pump-amplifier-free generation of twin-beam intensity-difference squeezing. We directly observe optical squeezing approaching 3 dB in both bands, with quantum noise reduction extending to analysis frequencies of nearly 100 MHz. Furthermore, our phenomenological model of the power-dependent squeezing dynamics captures the competition among fundamental quantum correlations, detuning-locking jitter, and classical excess noise. Armed with these physical insights and our optimized low-threshold architecture, we successfully bridge the gap between macroscopic quantum squeezing and stringent on-chip power budgets, providing a practical, scalable pathway toward fully monolithic, directly diode-pumped continuous-variable quantum light sources.
Squeezed states of light are essential for emerging quantum technology in metrology and information processing. Chip-integrated photonics offers a route to scalable and efficient squeezed light generation, however, parasitic nonlinear processes and optical losses remain significant challenges. Here, we demonstrate single-mode quadrature squeezing in a photonic crystal microresonator via degenerate dual-pump spontaneous four-wave mixing. Implemented in a scalable, low-loss silicon-nitride photonic-chip platform, the microresonator features a tailored nano-corrugation that modifies its resonances to suppress parasitic nonlinear processes. In this way, we achieve an estimated 7.8 dB of on-chip squeezing in the bus waveguide, with potential for further improvement. These results open a promising pathway toward integrated squeezed light sources for quantum-enhanced interferometry, Gaussian boson sampling, coherent Ising machines, and universal quantum computing.
Quantum noise limits the sensitivity of optical measurements, but squeezed states of light enable quantum-enhanced metrology, sensing, and information processing. Most on-chip squeezed-light sources rely on Kerr (χ(3)χ^{(3)}χ(3)) nonlinearities, remain limited by pump power and excess loss constraints. Quadratic (χ(2)χ^{(2)}χ(2)) platforms instead provide stronger parametric interactions, lower pump power requirements, and greater spectral engineering flexibility. Here, we demonstrate strong, broadband squeezed-light generation on a thin-film lithium niobate (TFLN) photonic chip using a dual-resonant optical parametric amplifier implemented in a single periodically poled LN (PPLN) microresonator. Near-full-depth domain inversion is achieved simultaneously with highly over-coupled resonances, exhibiting escape efficiencies exceeding 90% and intrinsic quality factors above 2.5 million in a 0.6 mm2^22 X-cut TF-PPLN resonator, enabling efficient squeezing at 1587 nm when pumped at 793.5 nm. Operating in the continuous-wave regime, we directly measure -0.81 dB of squeezing below the shot-noise limit with a pump power of 27 mW, together with +4.29 dB of anti-squeezing. From these measurements, we infer an on-chip squeezing level of -7.52 dB ±\pm± 0.22 dB (95% confidence interval: [-7.96,-7.10] dB), and an on-chip anti-squeezing level of +9.62 dB ±\pm± 0.25 dB. We demonstrate single-mode squeezing at degeneracy with a squeezed-light spectrum exceeding 10.3 THz. This work reports the highest squeezing ratio among integrated χ(2)χ^{(2)}χ(2) cavity platforms and the first quasi-phase matched, fully resonant χ(2)χ^{(2)}χ(2) cavity squeezer on chip, establishing a scalable route to fully integrated power-efficient squeezed-light sources for quantum-enhanced sensing and metrology.