Scientists have demonstrated a significant advance in distributed quantum sensing, an emerging application of quantum networking. Using an integrated photonic circuit, they have achieved enhanced precision in measuring linear functions of four phase shifts. This accomplishment addresses a key limitation of previous experiments, which were hampered by bulky bulk-optic architectures, hindering their scalability.

Key to this advance is the use of squeezed states of light, which are a prime resource for experimental demonstrations of entanglement-enhanced quantum sensing, due to their ability to be deterministically generated and entangled. The experiment generated a four-mode entangled state on-chip, with entanglement verification and phase sensing also performed on-chip using an array of four integrated homodyne detectors.

The results show a remarkable improvement in precision: 0.199(16) dB below the shot noise limit, compared to 0.041(18) dB obtained with separable states. This represents a substantial enhancement in the capability of distributed quantum sensors to measure parameters with greater accuracy. Integrated photonics offers a compact and scalable platform, making it a promising solution for the development of future quantum sensors.