Dispersive Qubit Readout of Temperature

TL;DR

This paper explores how squeezed light techniques, specifically injected external squeezing and intracavity squeezing, can exponentially enhance the precision of temperature measurement in quantum systems, especially under certain thermal and interaction conditions.

Contribution

It demonstrates that combining IES and ICS can exponentially improve temperature measurement precision, extending quantum readout techniques to thermometry.

Findings

Exponential improvement in temperature measurement precision with squeezed light.

Heisenberg scaling achievable with multiple interacting qubits and specific cavity conditions.

Further enhancement of temperature measurement precision using IES.

Abstract

Squeezed light can exponentially increase the signal-to-noise ratio (SNR) of dispersive qubit readout, especially using a combination of injected external squeezing (IES) and intracavity squeezing (ICS). We further investigate whether IES and ICS can also exponentially improve the measurement precision of temperature. In the case of fully thermalized qubits isolated from thermal bath, the measurement precision of temperature can be improved exponentially when the temperature or measurement time or the input photon number approaches 0. In general, thermal fluctuations prevent the action of squeezed light. When multiple qubits maintain interacting with the thermal bath, the Heisenberg scaling can be achieved if the loss rate of the cavity is large and the coupling between the qubit and the optical cavity is weak enough. In the meantime, IES can also further promote the improvement of the measurement precision of the temperature exponentially.