# Quantum memory and non-demolition measurement of single phonon state with nitrogen-vacancy centers ensemble

## TL;DR

This paper proposes a method for quantum non-demolition measurement and memory of single phonons in diamond using NV centers, achieving high fidelity and overlap in phonon state transfer.

## Contribution

It introduces a novel scheme utilizing strain-induced coupling in diamond NV centers for efficient phonon quantum memory and QND measurement.

## Key findings

- High fidelity (up to 98.57%) in phonon state transfer.
- Effective phonon absorption and emission by NV centers ensemble.
- Numerical simulations confirm scheme feasibility under realistic conditions.

## Abstract

In diamond, the mechanical vibration induced strain can lead to interaction between the mechanical mode and the nitrogen-vecancy (NV) centers. In this work, we propose to utilize the strain induced coupling for the quantum non-demolition (QND) single phonon measurement and memory in diamond. The single phonon in a diamond mechanical resonator can be perfectly absorbed and emitted by the NV centers ensemble (NVE) with adiabatically tuning the microwave driving. An optical laser drives the NVE to the excited states, which have much larger coupling strength to the mechanical mode. By adiabatically eliminating the excited states under large detuning limit, the effective coupling between the mechanical mode and the NVE can be used for QND measurement of the single phonon state. Under realistic experimental conditions, we numerically simulate the scheme. It is found that the fidelity of the absorbing and emitting process can reach a much high value. The overlap between the input and the output phonon shapes can reach $98.57\%$.