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Advanced Photonics Nexus

Squeezed-light generation in thin-film silicon nitride photonic integrated chips

Shuai Liu, Abdulkarim Hariri, Kailu Zhou, Yuheng Zhang, DeYuan Hu, Nicholas Reynolds, Zheshen Zhang

Published Mar 14, 2026• 0 citations
Publisher

Abstract

Squeezed light is a fundamental resource for a broad spectrum of quantum technologies, including precision metrology, secure communication, and quantum simulation and computing. The integration of squeezed-light sources with photonic circuits presents a transformative approach—not only offering compactness, stability, and scalability, but also enabling seamless high-fidelity on-chip generation, manipulation, and processing of quantum states without being hampered by inter-component quantum decoherence arising from loss and noise. In this work, we report the experimental generation of a two-mode squeezed vacuum state on a thin-film silicon-nitride photonic integrated circuit with normal group velocity dispersion of 6.3×105 fs2/m. Quadrature squeezing of −2.1 dB±0.09 dB and anti-squeezing of 7.1 dB±0.04 dB are directly measured. To fully understand the dynamics of the quantum process, a comprehensive theoretical model is developed to capture the squeezing performance, showing excellent agreement with experimental results. Our findings highlight the potential of the thin-film silicon nitride platform that capitalizes on fully foundry-compatible fabrication technologies to advance robust, large-scale, and manufacturing-ready quantum information processing systems.

DOI
10.1117/1.apn.5.2.026019

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Squeezed light are optical beams with variance below the Shot Noise Level. They are a key resource for quantum technologies based on photons, they can be used to achieve better precision measurements, improve security in quantum key distribution channels and as a fundamental resource for quantum computation. To date, the majority of experiments based on squeezed light have been based on non-linear crystals and discrete optical components, as the integration of quadrature squeezed states of light in a nanofabrication-friendly material is a challenging technological task. Here we measure 0.45 dB of GHz-broad quadrature squeezing produced by a ring resonator integrated on a Silicon Nitride photonic chip that we fabricated with CMOS compatible steps. The result corrected for the off-chip losses is estimated to be 1 dB below the Shot Noise Level. We identify and verify that the current results are limited by excess noise produced in the chip, and propose ways to reduce it. Calculations suggest that an improvement in the optical properties of the chip achievable with existing technology can develop scalable quantum technologies based on light.
Squeezed light is a key quantum resource that enables quantum advantages for sensing, networking, and computing applications. The scalable generation and manipulation of squeezed light with integrated platforms are highly desired for the development of quantum technology with continuous variables. In this Letter, we demonstrate squeezed light generation with thin-film lithium niobate integrated photonics. Parametric down-conversion is realized with quasi-phase matching using ferroelectric domain engineering. With sub-wavelength mode confinement, efficient nonlinear processes can be observed with single-pass configuration. We measure 0.56 ± 0.09 dB quadrature squeezing (∼2.6 dB inferred on-chip). The single-pass configuration further enables the generation of squeezed light with large spectral bandwidth up to 7 THz. This work represents a significant step towards the on-chip implementation of continuous-variable quantum information processing.
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Quantum resources such as squeezed and entangled states of light provide a pathway to surpass classical sensitivity limits in measurement and information processing. This thesis presents the development and application of engineered squeezed light sources across both bulk and integrated photonic platforms, demonstrating their utility in advancing quantum-enhanced metrology for spectroscopy and inertial sensing. In the first experimental platform, I introduce entangled dual-comb spectroscopy (EDCS), which integrates squeezed light with dual-comb architectures. By exploiting entanglement across comb lines, EDCS circumvents the shot-noise limitations of classical dual-comb spectroscopy. My experiment demonstrate a 2.6 dB improvement in signal-to-noise ratio and a 1.7-fold reduction in integration time, establishing EDCS as a powerful tool for rapid and precise chemical and biological sensing. The second platform applies squeezed light to resonant fiber optic gyroscopes (RFOGs), where quantum fluctuations typically impose a fundamental noise floor. By injecting bright amplitude-squeezed light into the resonator, I achieve a 2 dB reduction in detector noise, verified via Allan deviation analysis. This quantum-enhanced RFOG architecture shows that squeezed light can improve sensitivity under practical operational conditions, paving the way for next-generation inertial navigation systems. Finally, I demonstrate the on-chip generation of squeezed light using silicon nitride photonic circuits. Thin-film devices achieve more than 2 dB of quadrature squeezing with excellent agreement between experiment and theory, while wafer-scale thick-film devices yield reproducible 3 dB squeezing across multiple dies with sub-0.2 dB variation. These results establish silicon nitride as a CMOS-compatible platform for scalable and manufacturable quantum light sources, offering a route toward robust, large-scale quantum photonic technologies. Together, these results bridge the gap between laboratory demonstrations and deployable quantum-enhanced measurement systems. By advancing both free-space and integrated implementations of squeezed light, this work provides foundational steps toward practical quantum technologies for precision navigation, spectroscopy, and information processing.