Researchers from the Institute for Molecular Engineering (IME) have demonstrated that macroscopic entanglement can be generated at room temperature and in a small magnetic field. The research has been published in Science Advances.
Entanglement is a key resource for quantum computers, quantum-communication networks, and high-precision sensors. Macroscopic spin ensembles have been historically important in the development of quantum algorithms for these prospective technologies and remain strong candidates for implementing them today. This strength derives from their long-lived quantum coherence, strong signal, and ability to couple collectively to external degrees of freedom. Nonetheless, preparing ensembles of genuinely entangled spin states has required high magnetic fields and cryogenic temperatures or photochemical reactions.
We demonstrate that entanglement can be realized in solid-state spin ensembles at ambient conditions. We use hybrid registers comprising of electron-nuclear spin pairs that are localized at color-center defects in a commercial SiC wafer. We optically initialize 103 identical registers in a 40-μm3 volume (with fidelity) and deterministically prepare them into the maximally entangled Bell states (with 0.88 ± 0.07 fidelity). To verify entanglement, we develop a register-specific quantum-state tomography protocol. The entanglement of a macroscopic solid-state spin ensemble at ambient conditions represents an important step toward practical quantum technology.
Paul V. Klimov, Abram L. Falk, David J. Christle, Viatcheslav V. Dobrovitski and David D. Awschalom, “Quantum Entanglement at Ambient Conditions in a Macroscopic Solid-state Spin Ensemble,” Science Advances 20 Nov 2015: Vol. 1, no. 10, e1501015, DOI: 10.1126/sciadv.1501015 , Published Online November 20, 2015.