On-chip quantum NOON state sensing for temperature and humidity

A maximal photon number entangled state, namely NOON state, can be adopted for sensing with a quantum enhanced precision. In this work, we designed silicon quantum photonic chips containing two types of Mach–Zehnder interferometers wherein the two-photon NOON state, sensing element for temperature or humidity, is generated. Compared with classical light or single photon case, two-photon NOON state sensing shows a solid enhancement in the sensing resolution and precision. As the first demonstration of on-chip quantum photonic sensing, it reveals the advantages of photonic chips for high integration density, small-size, stability for multiple-parameter sensing serviceability. A higher sensing precision is expected to beat the standard quantum limit with a higher photon number NOON state.