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Discovery of ST1 centers in natural diamond

Priyadharshini Balasubramanian, Mathias H. Metsch, Reddy Prithvi, Lachlan J. Rogers, Neil B. Manson, Marcus W. Doherty, Fedor Jelezko

Published Aug 1, 2019• 25 citations
Publisher

Abstract

The ST1 center is a point defect in diamond with bright fluorescence and a mechanism for optical spin initialization and readout. The center has impressive potential for applications in diamond quantum computing as a quantum bus to a register of nuclear spins. This is because it has an exceptionally high readout contrast, and unlike the well-known nitrogen-vacancy center, it does not have a ground state electronic spin that decoheres the nuclear spins. However, its chemical structure is unknown, and there are large gaps in our understanding of its properties. We present the discovery of ST1 centers in natural diamond. Our experiments identify interesting power dependence of the center’s optical dynamics and reveal new electronic structure. We also present a theory of its electron-phonon interactions, which we combine with previous experiments, to shortlist likely candidates for its chemical structure.

DOI
10.1515/nanoph-2019-0148

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The ST1 center is a point defect in diamond with bright fluorescence and a mechanism for optical spin initialization and readout. The center has impressive potential for applications in diamond quantum computing as a quantum bus to a register of nuclear spins. This is because it has an exceptionally high readout contrast, and unlike the well-known nitrogen-vacancy center, it does not have a ground state electronic spin that decoheres the nuclear spins. However, its chemical structure is unknown, and there are large gaps in our understanding of its properties. We present the discovery of ST1 centers in natural diamond. Our experiments identify interesting power dependence of the center’s optical dynamics and reveal new electronic structure. We also present a theory of its electron-phonon interactions, which we combine with previous experiments, to shortlist likely candidates for its chemical structure.
Abstract The ST1 center is a point defect in diamond with bright fluorescence and a mechanism for optical spin initialization and readout. The center has impressive potential for applications in diamond quantum computing as a quantum bus to a register of nuclear spins. This is because it has an exceptionally high readout contrast, and unlike the well‐known nitrogen‐vacancy center, it does not have a ground state electronic spin that decoheres the nuclear spins. However, its chemical structure is unknown, and there are large gaps in our understanding of its properties. We present the discovery of ST1 centers in natural diamond. Our experiments identify interesting power dependence of the center’s optical dynamics and reveal new electronic structure. We also present a theory of its electron‐phonon interactions, which we combine with previous experiments, to shortlist likely candidates for its chemical structure.
Among hundreds of optically active solid-state defects, very few of them hold the promise of spin qubits coherently operating at room temperature. Besides the prominent nitrogen-vacancy (NV) center in diamond, the more recently discovered ST1 center possesses advantageous electronic and spin properties such as a spin-free ground state and a large spin readout contrast (>50%) at 300 K. However, because of its unknown nature, the ST1 center was never created on demand or computed theoretically. Here, we show that both oxygen and the lattice vacancy are constituents of the ST1 center. The involvement of oxygen is unambiguously proved from two independent experiments conducted on two different samples. The creation efficiency of ST1 at 1200 °C annealing is about 10 –5 for oxygen implantation of energy 6–50 keV. The addition of vacancies followed by a thermal treatment activate further oxygen into ST1 centers, as it does for native nitrogen into NV centers. Possible ST1 configurations are discussed. The ST1 creation competes with the likely more efficient formation of OV and OVH defects. The controlled fabrication of ST1 and NV centers opens up the way to scalable room-temperature hybrid qubit systems and universal nuclear spin gates.
The ST2 center is an optically addressable point defect in diamond that facilitates spin initialization and readout. However, while this study presents the discovery of ST2 centers first observed in a natural diamond and provides a reliable technique for artificially creating them, its chemical structure remains unknown. To assess the potential of ST2, we map out its basic optical characteristics, reveal its electronic level structure, and quantify the intrinsic transition rates. Furthermore, we investigate its response to microwaves, static magnetic fields, and the polarization of excitation laser light, revealing twelve inequivalent orientations of the ST2 center. Simultaneous exposure to microwaves and static magnetic fields also reveals an exceptionally wide acceptance angle for sensing strong magnetic fields, unlike the well-established NV center, which is sensitive only within a narrow cone aligned with its symmetry axis. This finding establishes the ST2 center as a highly promising candidate for nanoscale quantum sensing.
The ST2 center is an optically addressable point defect in diamond that facilitates spin initialization and readout at room temperature. However, while this study presents the discovery of photostable ST2 centers first observed in a natural diamond and provides a reliable technique for artificially creating them, its chemical structure remains unknown. To assess the potential of ST2, we map out its basic optical characteristics, reveal its electronic level structure, and quantify the intrinsic transition rates. Furthermore, we investigate its response to microwaves, static magnetic fields, and the polarization of excitation laser light, revealing twelve inequivalent orientations of the ST2 center. Simultaneous exposure to microwaves and static magnetic fields also reveals an exceptionally wide acceptance angle for sensing strong magnetic fields, unlike the well-established NV center, which is sensitive only within a narrow cone aligned with its symmetry axis. This finding establishes the ST2 center as a highly promising candidate for nanoscale quantum sensing.
Abstract The ST2 center is an optically addressable point defect in diamond that facilitates spin initialization and readout at room temperature. However, while this study presents the discovery of photostable ST2 centers first observed in a natural diamond and provides a reliable technique for artificially creating them, its chemical structure remains unknown. To assess the potential of ST2, we map out its basic optical characteristics, reveal its electronic level structure, and quantify the intrinsic transition rates. Furthermore, we investigate its response to microwaves, static magnetic fields, and the polarization of excitation laser light, revealing twelve inequivalent orientations of the ST2 center. Simultaneous exposure to microwaves and static magnetic fields also reveals an exceptionally wide acceptance angle for sensing strong magnetic fields, unlike the well-established NV center, which is sensitive only within a narrow cone aligned with its symmetry axis. This finding establishes the ST2 center as a highly promising candidate for nanoscale quantum sensing.
Point defects in diamond may act as quantum bits. Recently, oxygen-vacancy related defects have been proposed to the origin of the so-called ST1 color center in diamond that can realize a long-living solid-state quantum memory. Motivated by this proposal we systematically investigate oxygen-vacancy complexes in diamond by means of first principles density functional theory calculations. We find that all the considered oxygen-vacancy defects have a high-spin ground state in their neutral charge state, which disregards them as an origin for the ST1 color center. We identify a high-spin metastable oxygen-vacancy complex and characterize their magneto-optical properties for identification in future experiments.