Direct observation of 5 dB quantum noise squeezing from a SiN micro-ring with the aid of an on-chip parametric amplifier

Integration of quantum optical devices on a chip has been a goal to achieve scalable optical quantum computing and portable quantum sensing devices. Most efforts have focused on single/two-photon devices for discrete quantum information processing. Recently, more activities were seen in the on-chip generation of squeezed and EPR-type entangled states with micro-rings chi-3-nonlinear four-wave mixing, and with thin-film waveguides of chi-2-nonlinear frequency down conversion processes. These continuous variable quantum optical devices are suitable for quantum sensing purposes. However, the currently reported quantum noise reduction effects were limited to around 2 dB because of large coupling losses off the chip. On the other hand, it was recently shown [1,2,3,4] that a parametric amplifier can act as a measurement device to measure squeezing, which has the advantage of resilience to external losses and is particularly desirable in tackling the coupling loss issue for integrated optics application. In this work, we incorporate two independently controlled but directly coupled micro-rings on a SiN chip, with one serving as a squeezer for squeezed state generation and the other as a high-gain parametric amplifier for measurement. We achieved an observed quantum noise reduction of 5 dB. Such an on-chip device with two micro-rings can also serve as an SU(1,1) nonlinear interferometer which should find applications in quantum sensing.

[1] Y. Shaked et al., “Lifting the bandwidth limit of optical homodyne measurement with broadband parametric amplification,” Nat. Commun. 9, 609 (2018).

[2] Jiamin Li et al., “Pulsed entanglement measured by parametric amplifier assisted homodyne detection”, Optics Express 27, 030552 (2019).

[3] J. Li et al., “Measuring continuous-variable quantum entanglement with parametric amplifier assisted homodyne detection”, Phys. Rev. A 101, 053801 (2020).

[4] R. Nehra, R. Sekine, L. Ledezma, et al. “Few-cycle vacuum squeezing in nanophotonics,” Science 377, 1333 (2022).