Quadrature squeezing in a nanophotonic microresonator

Nat. Commun. 16, 10791 (2025) · DOI: 10.1038/s41467-025-66703-x

License: CC BY 4.0.

Abstract

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.

Figures

8 panels with data across 2 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

Illustrative figure, no extractable data. Shown in the paper PDF.

Fig. 2

• panel (a): Simulated shot-noise normalized variance (dB) against offset frequency $\Omega$ (units $\kappa/2$) for splittings $\beta=0$ (red), $\beta=5$ (yellow) and $\beta=15$ (dark blue): squeezing as solid lines, antisqueezing as dashed lines. The black dashed line at $-10$ dB is the deterministic bound for $\eta = 0.9$; the solid black line marks 0 dB. data.csv
• panel (b): Transmission, power (a.u.), against wavelength (nm) during a laser scan across several resonances of the photonic crystal ring resonator. The printed labels of the dips ($X_{-2}$, $P_{-1}$, $S$, $P_1$, $X_2$) are not shown. data.csv
• panel (c-1): Zoom on mode $X_{-2}$: power (a.u.) against frequency detuning (GHz) from the centre of the split resonance, showing the two dips of the split mode. data.csv
• panel (c-2): Zoom on mode $X_2$: power (a.u.) against frequency detuning (GHz) from the centre of the split resonance, showing the two dips of the split mode. data.csv
• panel (d): Measured mode splitting $2\gamma$ (GHz) against designed corrugation amplitude (nm) for modes $X_{-2}$ (yellow), $X_2$ (red) and $S$ (dark blue), as points. data.csv

Fig. 3

• panel (b): Measured shot-noise normalized quadrature variance (dB) of the single-mode squeezed vacuum against time (s) as the local-oscillator phase is swept, at 27 mW total pump power and 20 MHz sideband frequency. data.csv
• panel (c): Measured squeezing (dark blue) and antisqueezing (red) variance (dB) at 20 MHz sideband frequency against total on-chip pump power (mW), with the fit curves. Error bars are 1$\sigma$ confidence intervals. data.csv
• panel (d): Measured squeezing spectrum (dark blue), variance (dB) against offset frequency $\Omega$ (MHz) at 33 mW total pump power, corrected for the detector efficiency and dark noise clearance, with the simulated squeezing (yellow) and antisqueezing (red) spectra. data.csv

Cite

Alexander E. Ulanov, Bastian Ruhnke, Thibault Wildi, Tobias Herr. Quadrature squeezing in a nanophotonic microresonator. Nat. Commun. 16, 10791 (2025). https://doi.org/10.1038/s41467-025-66703-x

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