Spin quantum number as quantum resource for quantum sensing

Abstract

Identifying quantum resources for quantum sensing is of paramount importance. Up to date, two quantum resources has been widely recognized: the number $N$ of entangled quantum probes and the coherent evolution time $T$. Here we identify the spin quantum number $S$ of high-spin systems as another quantum resource, which can improve the sensing precision of magnetic field according to the Heisenberg scaling in the absence of noises. Similar to the case of $N$ and $T$, the utility of $S$ may be degraded by environmental noises. We analyze this point sysmatically under the Ornstein-Uhlenbeck noise (a prevalent noise in realistic physical systems). We find that the utility of $S$ vanishes in Markovian noises, but survives in non-Markovian noises, where it improves the sensing precision according to the classical scaling $1/\sqrt{S}$. Super-classical scaling can be achieved by suitable control of the high-spin system.