Quantum Coherence between High Spin Superposition States of Single Molecule Magnet Ni$_4$

TL;DR

This paper investigates quantum coherence in a single molecule magnet Ni$_4$, measuring energy splittings, decoherence rates, and relaxation times using microwave spectroscopy, revealing long-lived spin states relevant for quantum information.

Contribution

It provides the first direct measurements of spin coherence and relaxation times in Ni$_4$ SMMs, demonstrating long coherence times and energy-dependent relaxation.

Findings

Energy splittings between superposition states measured

Decoherence rates bounded by absorption linewidths

Spin-lattice relaxation times are on the order of seconds

Abstract

Magnetic quantum tunneling in a single molecule magnet (SMM) has been studied in experiments that combine microwave spectroscopy with high sensitivity magnetic measurements. By monitoring spin-state populations in the presence of microwave magnetic fields, the energy splittings between low lying high spin superposition states of SMM Ni$_4$ ($S$ = 4) have been measured. Absorption linewidths give an upper bound on the rate of decoherence. Pulsed microwave experiments provide a direct measure of the spin-lattice relaxation time, which is found to be remarkably long ($\sim$sec) and to increase with the energy splitting.