Ramsey interferometry with a spin embedded in a Coulomb chain

TL;DR

This paper demonstrates how to use Ramsey interferometry on a single ion's spin to probe the statistical and correlation properties of a Coulomb crystal, especially near phase transitions.

Contribution

It introduces a method to measure Coulomb crystal properties via spin-based interferometry, linking quantum measurements to many-body physics.

Findings

Interferometric contrast loss reveals crystal autocorrelation functions.

Method detects critical behavior near phase transition.

Provides a new quantum sensing technique for Coulomb crystals.

Abstract

We show that the statistical properties of a Coulomb crystal can be measured by means of a standard interferometric procedure performed on the spin of one ion in the chain. The ion spin, constituted by two internal levels of the ion, couples to the crystal modes via spatial displacement induced by photon absorption. The loss of contrast in the interferometric signal allows one to measure the autocorrelation function of the crystal observables. Close to the critical point, where the chain undergoes a second-order phase transition to a zigzag structure, the signal gives the behaviour of the correlation function at the critical point.