Experimental protection of the coherence of a molecular qubit exceeding a millisecond

TL;DR

This paper demonstrates that using dynamical decoupling, the coherence time of a molecular qubit can be extended beyond one millisecond, significantly improving its potential for quantum computing applications.

Contribution

The study introduces a physical dynamical decoupling method to extend molecular qubit coherence times beyond chemical limitations, achieving a record $T_2$ of 1.4 ms.

Findings

Coherence time $T_2$ exceeded 1.4 ms using dynamical decoupling.

Single qubit figure of merit $Q_M$ reached $1.4 imes 10^5$, 40 times higher than previous.

Molecular qubits with millisecond coherence times are promising for quantum information processing.

Abstract

There are several important solid-state systems, such as defects in solids, superconducting circuits and molecular qubits, for attractive candidates of quantum computations. Molecular qubits, which benefit from the power of chemistry for the tailored and inexpensive synthesis of new systems, face the challenge from decoherence effect. The decoherence effect is due to the molecular qubits' inevitable interactions to their environment. Strategies to overcome decoherence effect have been developed, such as designing a nuclear spin free environment and working at atomic clock transitions. These chemical approaches, however, have some fundamental limitations. For example, chemical approach restricts the ligand selection and design to ligands with zero nuclear magnetic dipole moment, such as carbon, oxygen, and sulfur. Herein, a physical approach, named Dynamical decoupling (DD), is utilized to combat decoherence, while the limitations of the chemical approaches can be avoided. The phase memory time $T_2$ for a transition metal complex has been prolonged to exceed one millisecond ($1.4~$ms) by employing DD. The single qubit figure of merit $Q_M $ reaches $ 1.4\times 10^5$, which is $40$ times better than that previously reported value for such system. Our results show that molecular qubits, with milliseconds $T_2$, are promising candidates for quantum information processing.