# A Clock Transition in the Cr$_7$Mn Molecular Nanomagnet

## TL;DR

This paper reports the discovery of a clock transition in the Cr$_7$Mn molecular nanomagnet, which can significantly enhance qubit coherence times by reducing environmental decoherence effects.

## Contribution

The study identifies and characterizes a zero-field clock transition in Cr$_7$Mn, demonstrating its potential to improve quantum coherence in molecular nanomagnet qubits.

## Key findings

- Maximum $T_2$ of ~350 ns at 1.8 K observed
- Evidence of clock transition effects from ESR experiments
- Potential for further $T_2$ improvements discussed

## Abstract

A viable qubit must have a long coherence time $T_2$. In molecular nanomagnets $T_2$ is often limited at low temperatures by the presence of dipole and hyperfine interactions, which are often mitigated through sample dilution, chemical engineering and isotope substitution in synthesis. Atomic-clock transitions offer another route to reducing decoherence from environmental fields by reducing the effective susceptibility of the working transition to field fluctuations. The Cr$_7$Mn molecular nanomagnet, a heterometallic ring, features a clock transition at zero field. Both continuous-wave and spin-echo electron-spin resonance experiments on Cr$_7$Mn samples diluted via co-crystallization, show evidence of the effects of the clock transition with a maximum $T_2\sim350$ ns at 1.8 K. We discuss improvements to the experiment that may increase $T_2$ further.