Quantum interference of single photons from remote nitrogen-vacancy centers in diamond

TL;DR

This paper demonstrates quantum interference between photons emitted by two separate nitrogen-vacancy centers in diamond, showing potential for quantum networking with solid-state qubits.

Contribution

It reports the first observation of quantum interference between remote NV centers and techniques to tune their emission into resonance.

Findings

Measured a second-order cross-correlation $g^{(2)}(0) = 0.35 \\pm 0.04<0.5

Achieved resonance tuning of NV centers with electric fields

Discussed extension to entangle remote solid-state qubits

Abstract

We demonstrate quantum interference between indistinguishable photons emitted by two nitrogen-vacancy (NV) centers in distinct diamond samples separated by two meters. Macroscopic solid immersion lenses are used to enhance photon collection efficiency. Quantum interference is verified by measuring a value of the second-order cross-correlation function $g^{(2)}(0) = 0.35 \pm 0.04<0.5$. In addition, optical transition frequencies of two separated NV centers are tuned into resonance with each other by applying external electric fields. Extension of the present approach to generate entanglement of remote solid-state qubits is discussed.