Coherent manipulation of dipolar coupled spins in an anisotropic environment

TL;DR

This paper investigates the coherent control of dipolar coupled spin qubits in anisotropic environments, developing a microscopic theory of spin relaxation, and demonstrating experimental validation with rare earth ions in crystals.

Contribution

It introduces a microscopic model for spin relaxation in anisotropic environments and links the magnetic field direction to coherence performance, supported by experimental data.

Findings

Decoherence rate is nonlinear in Rabi frequency.

Optimal magnetic field direction enhances qubit coherence.

Experimental Rabi oscillations match theoretical predictions.

Abstract

We study coherent dynamics in a system of dipolar coupled spin qubits diluted in solid and subjected to a driving microwave field. In the case of rare earth ions, anisotropic crystal background results in anisotropic g tensor and thus modifies the dipolar coupling. We develop a microscopic theory of spin relaxation in transient regime for the frequently encountered case of axially symmetric crystal field. The calculated decoherence rate is nonlinear in Rabi frequency. We show that the direction of static magnetic field that corresponds to the highest spin g-factor is preferable in order to obtain higher number of coherent qubit operations. The results of calculations are in excellent agreement with our experimental data on Rabi oscillations recorded for a series of CaWO4 crystals with different concentrations of Nd3+ ions.