Enhancing Spin Coherence in Optically Addressable Molecular Qubits through Host-Matrix Control

TL;DR

This paper demonstrates how host-matrix engineering can significantly enhance spin coherence times in optically addressable molecular qubits, enabling their use in quantum sensing applications.

Contribution

It introduces a method to control spin coherence via host environment modification, generating noise-insensitive clock transitions in molecular qubits.

Findings

Spin coherence times exceed 10 microseconds in engineered host matrices.

Host-matrix engineering creates noise-insensitive clock transitions not present in isostructural hosts.

Theoretical models accurately predict the dependence of coherence on zero-field splitting.

Abstract

Optically addressable spins are a promising platform for quantum information science due to their combination of a long-lived qubit with a spin-optical interface for external qubit control and read out. The ability to chemically synthesize such systems - to generate optically addressable molecular spins - offers a modular qubit architecture which can be transported across different environments, and atomistically tailored for targeted applications through bottom-up design and synthesis. Here we demonstrate how the spin coherence in such optically addressable molecular qubits can be controlled through engineering their host environment. By inserting chromium (IV)-based molecular qubits into a non-isostructural host matrix, we generate noise-insensitive clock transitions, through a transverse zero-field splitting, that are not present when using an isostructural host. This host-matrix engineering leads to spin-coherence times of more than 10 microseconds for optically addressable molecular spin qubits in a nuclear and electron-spin rich environment. We model the dependence of spin coherence on transverse zero-field splitting from first principles and experimentally verify the theoretical predictions with four distinct molecular systems. Finally, we explore how to further enhance optical-spin interfaces in molecular qubits by investigating the key parameters of optical linewidth and spin-lattice relaxation time. Our results demonstrate the ability to test qubit structure-function relationships through a tunable molecular platform and highlight opportunities for using molecular qubits for nanoscale quantum sensing in noisy environments.