Critical quantum metrology robust against dissipation and non-adiabaticity
arxiv(2024)
摘要
Critical systems near quantum phase transitions were predicted to be useful
for improvement of metrological precision, thanks to their ultra-sensitive
response to a tiny variation of the control Hamiltonian. Despite the promising
perspective, realization of criticality-enhanced quantum metrology is an
experimentally challenging task, mainly owing to the extremely long time needed
to encode the signal to some physical quantity of a critical system. We here
circumvent this problem by making use of the critical behaviors in the
Jaynes-Cummings model, comprising a single qubit and a photonic resonator, to
which the signal field is coupled. The information about the field amplitude is
encoded in the qubit's excitation number in the dark state, which displays a
divergent changing rate at the critical point. The most remarkable feature of
this critical sensor is that the performance is insensitive to the leakage to
bright eigenstates, caused by decoherence and non-adiabatic effects. We
demonstrate such a metrological protocol in a superconducting circuit, where an
Xmon qubit, interacting with a resonator, is used as a probe for estimating the
amplitude of a microwave field coupled to the resonator. The measured quantum
Fisher information exhibits a critical quantum enhancement, confirming the
potential of this system for quantum metrology.
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