Indirect methods to control population distribution in a large spin system

Abstract

We demonstrate how a large spin system ( = S 7 2) 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 Gd 3+ impurity ion ensemble in a YVO 4 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.

Quantum Control via Landau-Zener-Stückelberg-Majorana Transitions

“…However, sometimes, only the dynamics of two close levels is relevant. We find this in the work of (Zhao et al, 2017) on a large-spin system, S = 7/2. The authors observed the nonadiabatic dynamics around one of the avoided-level crossings controlled with an external magnetic field in a Gd 3+ impurity ion ensemble, which makes a qubit system with "a virtually unlimited relaxation time".…”