Adiabatic refocusing of nuclear spins in Tm3+:YAG

TL;DR

This paper demonstrates a method to measure nuclear spin concentration in Tm3+:YAG using optical absorbance detection of spin echoes, employing adiabatic pulses to efficiently rephase spins at low power.

Contribution

It introduces an optical absorbance-based technique for directly measuring spin concentration and employs adiabatic pulses to rephase spins in a broad inhomogeneous line, reducing power requirements.

Findings

Successful measurement of spin concentration via optical absorbance.

Effective rephasing of spins with low-power adiabatic pulses.

Potential for improved quantum memory protocols.

Abstract

We show that the optical absorbance detection of nuclear spin echo gives direct access to the spin concentration, unlike most coherent signal detection techniques where the signal intensity/amplitude is difficult to connect experimentally with the spin concentration. This way we measure the spin refocusing efficiency in a crystal of Tm$^{3+}$:YAG. Given the large inhomogeneous broadening of the spin transition in this material, rephasing the spins with the usual hard pulse procedure would require excessively high radiofrequency power. Instead we resort to an adiabatic pulse sequence that perfectly returns the spins to their initial common orientation, at low power cost.