Improving the lifetime of the NV center ensemble coupled with a superconducting flux qubit by applying magnetic fields

TL;DR

This paper demonstrates that applying magnetic fields to NV center ensembles coupled with superconducting flux qubits enhances coherence times by reducing inhomogeneous broadening, supported by both theoretical modeling and experimental validation.

Contribution

It provides a theoretical model explaining how magnetic fields improve NV center coherence and experimentally confirms the enhancement of vacuum Rabi oscillation lifetime.

Findings

Magnetic fields suppress inhomogeneous broadening in NV centers.

Application of magnetic fields extends the lifetime of vacuum Rabi oscillations.

Theoretical model accurately reproduces experimental results.

Abstract

One of the promising systems to realize quantum computation is a hybrid system where a superconducting flux qubit plays a role of a quantum processor and the NV center ensemble is used as a quantum memory. We have theoretically and experimentally studied the effect of magnetic fields on this hybrid system, and found that the lifetime of the vacuum Rabi oscillation is improved by applying a few mT magnetic field to the NV center ensemble. Here, we construct a theoretical model to reproduce the vacuum Rabi oscillations with/without magnetic fields applied to the NV centers, and we determine the reason why magnetic fields can affect the coherent properties of the NV center ensemble. From our theoretical analysis, we quantitatively show that the magnetic fields actually suppress the inhomogeneous broadening from the strain in the NV centers.