Quantum Critical Environment Assisted Quantum Magnetometer

TL;DR

This paper explores how a qubit coupled to a critical Ising ring can serve as a highly sensitive quantum magnetometer, leveraging criticality to enhance measurement precision, especially near the phase transition.

Contribution

It demonstrates that a central qubit interacting with an Ising ring near criticality can significantly improve magnetic field estimation precision, showing Heisenberg-like scaling at zero temperature.

Findings

Heisenberg-like scaling achieved near critical point at zero temperature.

Finite temperature limits the scaling to smaller system sizes.

Non-unitary evolution enhances measurement accuracy.

Abstract

A central qubit coupled to an Ising ring of $N$ qubits, operating close to a critical point is investigated as a potential precision quantum magnetometer for estimating an applied transverse magnetic field. We compute the Quantum Fisher information for the central, probe qubit with the Ising chain initialized in its ground state or in a thermal state. The non-unitary evolution of the central qubit due to its interaction with the surrounding Ising ring enhances the accuracy of the magnetic field measurement. Near the critical point of the ring, Heisenberg-like scaling of the precision in estimating the magnetic field is obtained when the ring is initialized in its ground state. However, for finite temperatures, the Heisenberg scaling is limited to lower ranges of $N$ values.