• Open Access

Coupling a Surface Acoustic Wave to an Electron Spin in Diamond via a Dark State

D. Andrew Golter, Thein Oo, Mayra Amezcua, Ignas Lekavicius, Kevin A. Stewart, and Hailin Wang
Phys. Rev. X 6, 041060 – Published 20 December 2016

Abstract

The emerging field of quantum acoustics explores interactions between acoustic waves and artificial atoms and their applications in quantum information processing. In this experimental study, we demonstrate the coupling between a surface acoustic wave (SAW) and an electron spin in diamond by taking advantage of the strong strain coupling of the excited states of a nitrogen vacancy center while avoiding the short lifetime of these states. The SAW-spin coupling takes place through a Λ-type three-level system where two ground spin states couple to a common excited state through a phonon-assisted as well as a direct dipole optical transition. Both coherent population trapping and optically driven spin transitions have been realized. The coherent population trapping demonstrates the coupling between a SAW and an electron spin coherence through a dark state. The optically driven spin transitions, which resemble the sideband transitions in a trapped-ion system, can enable the quantum control of both spin and mechanical degrees of freedom and potentially a trapped-ion-like solid-state system for applications in quantum computing. These results establish an experimental platform for spin-based quantum acoustics, bridging the gap between spintronics and quantum acoustics.

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  • Received 2 August 2016

DOI:https://doi.org/10.1103/PhysRevX.6.041060

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied PhysicsQuantum Information, Science & Technology

Authors & Affiliations

D. Andrew Golter1, Thein Oo1, Mayra Amezcua1, Ignas Lekavicius1, Kevin A. Stewart2, and Hailin Wang1

  • 1Department of Physics, University of Oregon, Eugene, Oregon 97403, USA
  • 2School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, Oregon 97331, USA

Popular Summary

Quantum acoustics is an emerging field focusing on interactions between acoustic waves and artificial atoms that can be exploited in quantum science. Among the various artificial atoms or qubits that have been explored, spin qubits (e.g., nitrogen vacancy color centers in diamond) are of particular interest because of their robust spin coherence and the ease with which these qubits can be measured and controlled. Robust spin qubits necessarily require weak coupling between spin and acoustic vibrations to avoid rapid decay of the spin coherence. On the other hand, higher-energy excited states of nitrogen vacancy centers can couple strongly to acoustic waves via mechanical strain induced by the acoustic vibrations. These excited states, however, decay quickly to the lower-energy states and therefore are not suitable for use as qubits. Here, we report experimental advances that overcome this dilemma by coupling a surface acoustic wave to a nitrogen vacancy spin qubit through the excited states, but without populating these states, thereby avoiding the decay of the excited states.

Compared with optical waves, acoustic waves propagate at a speed 5 orders of magnitude slower, and they couple to artificial atoms via mechanical as well as electromagnetic interactions. These unique properties can pave the way for quantum operations and communications on a chip. A key aspect of coupling a surface acoustic wave strongly to a nitrogen vacancy spin qubit involves the optical preparation of the nitrogen vacancy center in a dark state. Using a three-level system and working at cryogenic temperatures, we take advantage of this dark state to trap the electron in ground spin states. We subject the ground spin states, which serve as the spin qubit, to the excited-state strain coupling via optical interactions. We find that ground spin states experience the strong excited-state strain coupling through optical interactions but are nearly immune to the decay of the excited state.

We expect that our findings will motivate future experimental realizations of spin-based quantum acoustics.

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Vol. 6, Iss. 4 — October - December 2016

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