Strong tunable spin-spin interaction in a weakly coupled nitrogen vacancy spin-cavity electromechanical system

TL;DR

This paper proposes a method to significantly enhance the interaction between two weakly coupled NV center spins in diamond using an electromechanical cavity, enabling strong, tunable spin-spin coupling for quantum information processing.

Contribution

It introduces a novel approach leveraging a critical point in the electromechanical subsystem to achieve strong, tunable coupling between NV spins in a weakly coupled system.

Findings

Enhanced spin-spin interaction via low-frequency polariton

Decoupling of high-frequency polariton from NV spin

Potential for coherent quantum information exchange

Abstract

The long coherence time of a single nitrogen vacancy (NV) center spin in diamond is a crucial advantage for implementing quantum information processing. However, the realization of strong coupling between single NV spins is challenging. Here we propose a method to greatly enchance the interaction between two single NV spins in diamond which are only weakly coupled to an electromechanical cavity. Owing to the presence of a critical point for the linearized electromechanical subsystem, the coupling between a single NV spin and the high-frequency polariton (formed by the mechanical and cavity modes) can be fully decoupled, but the coupling between the single NV spin and the low-frequency polariton is however greatly enhanced. Thus, AC Stark shift of the single NV spin can be measured. With the low-frequency polariton as a quantum bus, a strong coupling between two single NV centers is achievable. This effective strong coupling can ensure coherent quantum-information exchange between two spin qubits in the weakly coupled spin-cavity elecromechanical system.