Quantum precision sensing

Philippe Bouyer

Yinan Fang, Xing Mao Xiao, Chang-Pu Sun +2 more

Using a single quantum probe to sense other quantum objects offers distinct advantages but suffers from some limitations that may degrade the sensing precision severely, especially when the probe-target coupling is weak. Here we propose a strategy to improve the sensing precision by using the quantum probe to engineer the evolution of the target. We consider an exactly solvable model, in which a qubit is used as the probe to sense the frequency of a harmonic oscillator. We show that by applying adaptive periodic quantum control on the qubit, the sensing precision can be enhanced from 1/T scaling with the total time cost T to 1/T^{2} scaling, thus improving the precision by several orders of magnitudes. Such improvement can be achieved without any direct access to the oscillator and the improvement increases with decreasing probe-target coupling. This provides a useful routine to ultrasensitive quantum sensing of weakly coupled quantum objects.

Yuichiro Matsuzaki

Qigeng Duan, Teng Li, Siqi Chen +2 more

The diamond sensor has emerged as a promising platform for quantum sensing, enabling the estimation of physical quantities -- such as microwave~(MW) field -- with precision unattainable by classical counterpart. However, traditional diamond sensors suffer severe precision degradation when the signal MW is not resonant with the sensor transition frequency. Here, we propose and demonstrate a Floquet diamond sensor~(FDS) for high-precision off-resonant MW amplitude sensing without attenuating the strength of the signal MW. The periodic driven field effectively induces an quasi-energy shift that matches the off-resonant MW frequency. The measurement precision of FDS is characterized by quantum Fisher information, which approaches the ultimate precision -- Heisenberg limit -- within the coherent time. Furthermore, the FDS exhibits robust tolerance to practical control errors and is compatible with dynamical coupling protocol, enabling a robust and high-sensitivity magnetic sensing. Our results confirm the quantum advantage of quantum sensing and provide a practical technology for high-precision off-resonant MW sensing.

Weihong 伟宏 Luo 罗, Chao Wu, Yuxing 昱星 Du 杜 +5 more

Abstract 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.