Indirect methods to control population distribution in a large spin system

Lingfei Zhao,Maxim Goryachev,Jeremy Bourhill,Michael E Tobar

doi:10.1088/1367-2630/aa5fdd

Abstract

We demonstrate how a large spin system () with the ground and first excited state separated by a seven-photon transition exhibits nonequilibrium thermodynamic properties and how the population distribution may be manipulated using coupling between energy levels. The first method involves non-adiabatic passage through an avoided level crossing controlled with an external DC magnetic field and the resulting Landau–Zener transition. The second method is based on external cavity pumping to a higher energy state hybridised with another state that is two single-photon transitions away from the ground state. The results are confirmed experimentally with a Gd3+ impurity ion ensemble in a YVO4 crystal cooled to 20 mK, which also acts as a microwave photonic whispering gallery mode resonator. Extremely long lifetimes are observed due to the large number of photons required for the transition between the ground and first excited states.

Highlights

Physical systems based on the light–matter interaction in general and quantum electrodynamics (QED) with ‘spins-in-solid’ in particular have found a very broad range of applications
The unconventional level structure of Gd3+ ions in YVO4 crystal, with the two lowest energy levels split by a seven-photon transition, provides a qubit system with virtually unlimited relaxation time
At readily accessible temperature of around 20 mK and some external magnetic field, the energy splittings are such that only the ground state is populated at thermal equilibrium

Summary

10 March 2017

The first method the work, journal citation and DOI. Involves non-adiabatic passage through an avoided level crossing controlled with an external DC magnetic field and the resulting Landau–Zener transition. The second method is based on external cavity pumping to a higher energy state hybridised with another state that is two single-photon transitions away from the ground state. Impurity ion ensemble in a YVO4 crystal cooled to 20 mK, which acts as a microwave photonic whispering gallery mode resonator. Long lifetimes are observed due to the large number of photons required for the transition between the ground and first excited states

Introduction

Experimental realisation

Findings

Discussion