Curator's Take
AI Commentary
This article demonstrates the first monolithic SU(1,1) interferometer that measures on‑chip squeezing before it is degraded by fiber coupling loss, achieving a 4.6 dB noise reduction despite more than 5 dB of off‑chip attenuation. By embedding a high‑gain parametric amplifier directly after the silicon‑nitride micro‑ring source, the scheme makes squeezed‑light generation loss‑tolerant and thus far more practical for integrated quantum sensors and continuous‑variable computing architectures. The result bridges a key gap between laboratory‑scale squeezing experiments and scalable photonic chips, paving the way for on‑chip quantum metrology and fault‑tolerant CV operations.
— Mark Eatherly
Summary
Integration of quantum optical technique on-chip is crucial for large scale applications of quantum technology, which were proven in a free space environment to be superior to the corresponding classical technology. Squeezed states of light can be used for enhancing the sensitivity of quantum sensors and for fault-tolerant quantum computing. Although chip-based squeezed light generation has advanced significantly, practical impact remains limited because coupling losses between the chip and off-chip detectors destroy delicate quantum correlations, restricting the amount of observed squeezing. Here, we overcome this limitation by implementing the idea of on-chip quantum measurement with the aid of a parametric amplifier and applying it to the squeezed state generated by a silicon nitride (SiN) microring resonator. In our scheme, two matched SiN micro-rings are sequentially constructed. The first ring generates a squeezed state, whereas the second ring acts as a high-gain parametric amplifier (PA) that measures the squeezed state before the light experiences significant off-chip loss. This architecture is inherently loss-tolerant: the amplifier elevates the quantum noise well above the vacuum level, making the measurement insensitive to downstream losses. We directly observe a quantum noise reduction of 4.6 dB from the first ring, despite a chip-to-fiber coupling loss exceeding 5 dB. This work also demonstrates the first monolithic SU(1,1) interferometer with an estimated 5 dB signal-to-noise enhancement compared to traditional linear interferometers, and thus establishes a practical pathway for chip-based quantum sensors.