Quantum Rabi interferometry of motion and radiation

TL;DR

This paper introduces a hybrid Rabi interferometer for unambiguous phase space displacement estimation in oscillator-qubit systems, demonstrating superior sensitivity and robustness compared to traditional methods, without needing oscillator ground-state cooling.

Contribution

It proposes a novel hybrid Rabi interferometric scheme for displacement estimation in arbitrary phase space directions, surpassing existing single-mode and Jaynes-Cummings based methods.

Findings

Outperforms single-mode estimation schemes and conventional interferometers.

Sensitivity is independent of the oscillator's thermal occupation.

Robust against qubit dephasing and oscillator thermalization.

Abstract

The precise determination of a displacement of a mechanical oscillator or a microwave field in a predetermined direction in phase space can be carried out with trapped ions or superconducting circuits, respectively, by coupling the oscillator with ancilla qubits. Through that coupling, the displacement information is transferred to the qubits which are then subsequently read out. However, unambiguous estimation of displacement in an unknown direction in the phase space has not been attempted in such oscillator-qubit systems. Here, we propose a hybrid oscillator-qubit interferometric setup for the unambiguous estimation of phase space displacements in an arbitrary direction, based on feasible Rabi interactions beyond the rotating-wave approximation. Using such a hybrid Rabi interferometer for quantum sensing, we show that the performance is superior to the ones attained by single-mode estimation schemes and a conventional interferometer based on Jaynes-Cummings interactions. Moreover, we find that the sensitivity of the Rabi interferometer is independent of the thermal occupation of the oscillator mode, and thus cooling it to the ground state before sensing is not required. We also perform a thorough investigation of the effect of qubit dephasing and oscillator thermalization. We find the interferometer to be fairly robust, outperforming different benchmark estimation schemes even for large dephasing and thermalization.