Measurement based 2-qubit unitary gates for pairs of Nitrogen-Vacancy centers in diamond

TL;DR

This paper proposes a photon-scattering based method to implement high-fidelity two-qubit gates between Nitrogen-Vacancy centers in diamond, utilizing quantum interference and special drive frequencies to optimize gate performance.

Contribution

It introduces a novel photon scattering approach for NV center two-qubit gates, exploiting quantum interference and specific drive frequencies to enhance fidelity.

Findings

Gate fidelity can reach up to 97%.

Two special drive frequencies ('magic' and 'balanced') are identified.

The method enables a universal quantum gate set.

Abstract

The implementation of a high-fidelity two-qubit quantum logic gate remains an outstanding challenge for isolated solid-state qubits such as Nitrogen-Vacancy (NV) centers in diamond. In this work, we show that by driving pairs of NV centers to undergo photon scattering processes that flip their qubit state simultaneously, we can achieve a unitary two-qubit gate conditioned upon a single photon detection event. Further, by exploiting quantum interference between the optical transitions of the NV centers electronic states, we realize the existence of two special drive frequencies: a `magic' point where the spin-preserving elastic scattering rates are suppressed, and a `balanced' point where the state-flipping scattering rates are equal. We analyzed four different gate operation schemes that utilize these two special drive frequencies, and various combinations of polarization in the drive and collection paths. Our theoretical and numerical calculations show that the gate fidelity can be as high as 97%. The proposed unitary gate, combined with available single qubit unitary operations, forms a universal gate set for quantum computing.