Abstract Achieving a high level of pulsed squeezing, in a platform which offers integration and stability, is a key requirement for continuous-variable quantum information processing. Typically highly squeezed states are achieved with narrow band optical cavities and bulk crystals, limiting scalability. Using single-pass parametric down conversion in an integrated optical device, we demonstrate quadrature squeezing of picosecond pulses in a thin-film lithium niobate strip-loaded waveguide. For on-chip peak powers of less than 0.3 W, we measure up to −0.33 ± 0.07 dB of squeezing with an inferred on-chip value of −1.7 ± 0.4 dB. This work highlights the potential of the strip-loaded waveguide platform for broadband squeezing applications and the development of photonic quantum technologies.
Within the last decade, thin-film lithium niobate (TFLN) has emerged as a leading integrated photonics platform with immediate applications in classical communications. Concurrently, TFLN components tailored to the requirements of photonic quantum information processing have also garnered considerable interest. Chief among these is the quasi-phase matched (QPM) nonlinear frequency mixer—implemented via periodic domain inversion in ferroelectric lithium niobate—which can be used to generate photon pairs, squeezed states of light, and to perform single photon frequency conversion. Here, we demonstrate progress towards realizing a spectrally separable photon pair source in lithium niobate via waveguide dispersion engineering—a technique uniquely enabled by sub-wavelength optical mode confinement in the thin-film platform. Subsequently, we design optimize a scalable fabrication process to produce QPM TFLN devices for applications that require strict adherence to a specified operating wavelength, such as quantum frequency conversion in a quantum communications network. Finally, we explore how high-performance electro-optic devices can be combined with these nonlinear optical devices to realize a multi-functional platform in which quantum states of light can be generated and manipulated within a single, compact photonic integrated circuit.
Abstract 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)) nonlinearities, remain limited by pump power and excess loss constraints. Quadratic (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 0.6mm2 X-cut TF-PPLN resonator, enabling efficient squeezing at 1587nm 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 27mW, together with +4.29 dB of anti-squeezing. From these measurements, we infer an on-chip squeezing level of −7.52 dB±0.22 dB (95% confidence interval: [−7.96,−7.10] dB), and an on-chip anti-squeezing level of +9.62 dB±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) cavity platforms and the first quasi-phase matched, fully resonant χ(2) cavity squeezer on chip, establishing a scalable route to fully integrated power-efficient squeezed-light sources for quantum-enhanced sensing and metrology.
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)) nonlinearities, remain limited by pump power and excess loss constraints. Quadratic (
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 mm
2 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
± 0.22 dB (95% confidence interval: [-7.96,-7.10] dB), and an on-chip anti-squeezing level of +9.62 dB
± 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) cavity platforms and the first quasi-phase matched, fully resonant
χ(2) cavity squeezer on chip, establishing a scalable route to fully integrated power-efficient squeezed-light sources for quantum-enhanced sensing and metrology.
Squeezed states are essential for continuous-variable (CV) quantum information processing, with wide-ranging applications in computing, sensing, and communications. Integrated photonic circuits provide a scalable, convenient platform for building large CV circuits. Thin-film lithium niobate (TFLN) is particularly promising due to its low propagation loss, efficient parametric down conversion, and fast electro-optical modulation. In this work, we demonstrate a squeezed light source on an integrated TFLN platform, achieving a measured shot noise reduction of 0.46 dB (1.5 dB on-chip) using modal phase matching and grating couplers with an efficiency of up to −2.2 dB. The achieved squeezing is comparable to what has been observed using more complex circuitry based on periodic poling. The simpler design allows for compact, efficient, and reproducible sources of squeezed light.