Enhanced Quantum Metrology with Non-Phase-Covariant Noise

Jia-Xin Peng, Baiqiang Zhu, Weiping Zhang, Keye Zhang

Published 2024-04-12Version 1

The detrimental impact of noise on sensing performance in quantum metrology has been widely recognized by researchers in the field. However, there are no explicit fundamental laws of physics stating that noise invariably weakens quantum metrology. We reveal that phase-covariant (PC) noise either degrades or remains neutral to sensing precision, whereas non-phase-covariant (NPC) noise can potentially enhance parameter estimation, surpassing even the ultimate precision limit achievable in the absence of noise. This implies that a non-Hermitian quantum sensor may outperform its Hermitian counterpart in terms of sensing performance. To illustrate and validate our theory, we present several paradigmatic examples of magnetic field metrology.