Room temperature entanglement between distant single spins in diamond

TL;DR

This paper demonstrates room temperature entanglement between distant single spins in diamond, extending entanglement lifetime via nuclear spins, and showcases progress towards scalable quantum devices at ambient conditions.

Contribution

It reports the first experimental demonstration of entanglement between engineered single solid state spins in diamond at room temperature, with extended lifetime through nuclear spin entanglement.

Findings

Entanglement fidelity of 0.67 ± 0.04 achieved.

Electron spin entanglement lifetime extended to milliseconds.

Nuclear spin entanglement demonstrated over 25 nm distance.

Abstract

Entanglement is the central yet fleeting phenomena of quantum physics. Once being considered a peculiar counter-intuitive property of quantum theory it has developed into the most central element of quantum technology providing speed up to quantum computers, a path towards long distance quantum cryptography and increased sensitivity in quantum metrology. Consequently, there have been a number of experimental demonstration of entanglement between photons, atoms, ions as well as solid state systems like spins or quantum dots, superconducting circuits and macroscopic diamond. Here we experimentally demonstrate entanglement between two engineered single solid state spin quantum bits (qubits) at ambient conditions. Photon emission of defect pairs reveals ground state spin correlation. Entanglement (fidelity = 0.67 \pm 0.04) is proven by quantum state tomography. Moreover, the lifetime of electron spin entanglement is extended to ms by entanglement swapping to nuclear spins, demonstrating nuclear spin entanglement over a length scale of 25 nm. The experiments mark an important step towards a scalable room temperature quantum device being of potential use in quantum information processing as well as metrology.