Deterministic Bell state measurement with a single quantum memory

TL;DR

This paper demonstrates a deterministic and complete Bell state measurement using a nitrogen-vacancy center in diamond as a quantum memory, eliminating the need for extra qubits or isotopic purification, and enabling advancements in quantum networks.

Contribution

It introduces a novel method for deterministic Bell state measurement using only a single NV center without isotope dependence, leveraging electron-nitrogen qutrits at zero magnetic field.

Findings

Achieved deterministic Bell state measurement with a single NV center.

Operated in an isotope-free, field-free environment.

Paved the way for high-fidelity quantum repeaters and large-scale quantum networks.

Abstract

Any quantum information system operates with entanglement as a resource, which should be deterministically generated by a joint measurement known as complete Bell state measurement (BSM). The determinism arises from a quantum nondemolition measurement of two coupled qubits with the help of readout ancilla, which inevitably requires extra physical qubits. We here demonstrate a deterministic and complete BSM with only a nitrogen atom in a nitrogen-vacancy (NV) center in diamond as a quantum memory without reliance on any carbon isotopes by exploiting electron nitrogen (14N) double qutrits at a zero magnetic field. The degenerate logical qubits within the subspace of qutrits on the electron and nitrogen spins are holonomically controlled by arbitrarily polarized microwave and radiofrequency pulses via zero field split states as the ancilla, enabling the complete BSM deterministically. Since the system works under an isotope free and field free environment, the demonstration paves the way for realizing high yield, high fidelity, and high speed quantum repeaters for long haul quantum networks and quantum interfaces for large scale distributed quantum computers.