Electron Spin Relaxations in Biological [2Fe-2S] Cluster System

TL;DR

This study measures electron spin coherence times in biological [2Fe-2S] clusters, revealing long-lasting coherence affected by nuclear hyperfine interactions and demonstrating potential for quantum information applications.

Contribution

The paper provides the first detailed measurement of phase coherence relaxation times in biological [2Fe-2S] clusters, highlighting the impact of isotope labeling on extending coherence times.

Findings

T2 relaxation times reach up to 1.4 microseconds with isotope labeling.

Nuclear hyperfine interactions significantly influence spin coherence.

Coherent electron spin manipulation demonstrated through transient nutation experiments.

Abstract

The phase coherence relaxation times as long as $T_2\sim830-1030\pm20$ ns were measured for the [2Fe-2S] cluster in the intrinsic protein environment. This relaxation corresponds to a relatively long lasting coherence of the low-spin $S=1/2$ state. For this biological cluster, the phase coherence relaxation time was significantly affected by the nuclear hyperfine interactions of $^{14}$N with $I=1$. After labeling the cluster environments uniformly with the $^{15}$N isotope, $T_2$ exceeds $\sim1.1-1.4\pm0.1~\mu$s at the canonical orientations. This is already an order of magnitude longer than the duration of a single-spin qubit manipulation $\sim10-100$ ns. The transient nutation experiment corresponds to the coherent manipulation of the electron spin.