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arXiv:1612.02947 · Physical review. B./Physical review. B

Optical and microwave control of germanium-vacancy center spins in diamond

Petr Siyushev, Mathias H. Metsch, Aroosa Ijaz, Jan Binder, Mihir K. Bhaskar, Денис Дмитриевич Сукачев, Alp Sipahigil, Ruffin E. Evans, C. T. Nguyen, Mikhail D. Lukin, Philip Hemmer, Yuri N. Palyanov, Igor N. Kupriyanov, Yuri M. Borzdov, Lachlan J. Rogers, Fedor Jelezko

Published Aug 18, 2017• 171 citations
arXivHTMLPDF

Abstract

Novel solid-state qubits have a lot to offer for quantum information processing because of the potential simplicity of engineering quantum computational hardware similar to modern silicon-based electronics. This work presents optical and electron-spin properties of a novel germanium-vacancy defect in diamond. The defect center combines high brightness and exceptional spectral stability with microwave and optical access to electron spin. The combination of a spin-\textonehalf{} qubit and an optical interface makes possible of the germanium-vacancy defect in scalable quantum networks.

DOI
10.1103/physrevb.96.081201

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Novel solid-state qubits have a lot to offer for quantum information processing because of the potential simplicity of engineering quantum computational hardware similar to modern silicon-based electronics. This work presents optical and electron-spin properties of a novel germanium-vacancy defect in diamond. The defect center combines high brightness and exceptional spectral stability with microwave and optical access to electron spin. The combination of a spin-\textonehalf{} qubit and an optical interface makes possible of the germanium-vacancy defect in scalable quantum networks.
Abstract Solid-state spin defects, such as color centers in diamond, are among the most promising candidates for scalable and integrated quantum technologies. In particular, the good optical properties of silicon-vacancy centers in diamond, combined with naturally occurring and exceptionally coherent nuclear spins, serve as a building block for quantum networking applications. Here, we show that leveraging an ultra-high-strained silicon-vacancy center inside a nanodiamond allows us to coherently and efficiently control its electron spin, while mitigating phonon-induced dephasing at liquid helium temperature. Moreover, we indirectly control and characterize a 13C nuclear spin and establish a quantum register. We overcome limited nuclear spin initialization by implementing single-shot nuclear spin readout. Lastly, we demonstrate coherent optical control with GHz rates, thus opening a potential connection of the register to the optical domain. Our work paves the way for future integration of quantum network registers into conventional, well-established photonics and hybrid quantum communication systems.
Electron spin echoes were performed on nitrogen-vacancy $(\mathrm{N}\ensuremath{-}V)$ centers in diamond using optical polarization and detection and 35 GHz microwave control. The experiments demonstrate an approach to quantum information in the solid state. A phase memory time of $3.6 \ensuremath{\mu}\mathrm{s}$ was measured, and coupling of the electronic spin to the 14N{}^{14}\mathrm{N}14N nuclear spin was observed. Because of the favorable properties of the $\mathrm{N}\ensuremath{-}V$ center, interesting extensions of these single-qubit operations can be proposed.
Solid-state spin defects, such as color centers in diamond, are among the most promising candidates for scalable and integrated quantum technologies. In particular, the good optical properties of silicon-vacancy centers in diamond combined with naturally occurring and exceptionally coherent nuclear spins serve as a building block for quantum networking applications. Here, we show that leveraging an ultra-high strained silicon-vacancy center inside a nanodiamond allows us to coherently and efficiently control its electron spin, while mitigating phonon-induced dephasing at liquid helium temperature. Moreover, we indirectly control and characterize a 13C nuclear spin and establish a quantum register. We overcome limited nuclear spin initialization by implementing single-shot nuclear spin readout. Lastly, we demonstrate coherent optical control with GHz rates, thus connecting the register to the optical domain. Our work paves the way for future integration of quantum network registers into conventional, well-established photonics and hybrid quantum communication systems.
In the last decade atom-sized point defects in diamond, so called colour centres, have proven to be suitable systems for quantum information processing as well as quantum communication and sensing applications. Besides the wellknown nitrogen vacancy centre, the negatively charged silicon vacancy centre has recently proven to be a promising candidate due to its superior spectral properties such as narrow zero-phonon line widths and small phonon sidebands. In this feature article (article No.201700586) the authors summarize the center's electronic and optical properties as well as recent advances in controlling its quantum state using microwave as well as ultrafast all-optical control techniques which make it accessible for future quantum information processing applications. Moreover, the authors outline potential future experimental directions to improve the center's coherence time scale which so far is limited by phonon-induced decoherence. The cover picture shows an artistic representation of the silicon vacancy centre with its inversion-symmetric structure in a diamond crystal being addressed by an ultrashort laser pulse.
Point defects in semiconductors are becoming central to quantum technologies. They can be used as spin qubits interfacing with photons, which are fundamental for building quantum networks. Currently, the most prominent quantum defect in diamond is the nitrogen-vacancy (NV) center. However, it suffers from spectral diffusion that negatively impacts optical coherence and is due to the coupling of the emission energy with uncontrolled electric fields. The group IV vacancy complexes on the other hand have shown to be significantly more spectrally-stable as they are centrosymmetric and thus immune to the linear Stark shift. They however suffer from several issues ranging from low operation temperature to low optical efficiency due to dark states and difficulty in stabilizing the right defect charge state. Here we search for alternative to the group IV vacancy complex in diamond by systematically evaluating all possible vacancy complex using high-throughput first-principles computational screening. We identify the defects that combine centrosymmetry, emission in the visible range, as well as favorable and achievable electronic structure promoting higher operation temperature and defect levels well within the band gap. We find ZnV−2V^{-2}V−2 to be especially appealing.
The germanium vacancy in diamond (GeV) is a promising candidate for color center based quantum networking. Yet, like for other group-IV vacancy defects in diamond, achieving fast, high-fidelity qubit operations using traditional magnetic resonance techniques is experimentally challenging due to a weak magnetic dipole and susceptibility to thermally induced decoherence. Here, we perform all-optical control of the GeV and realize Rabi frequencies exceeding ∼ 20 MHz. We do so by driving the two Λ -systems of the GeV simultaneously and apply this to probe the spin coherence ( T 2 * = 224 ± 14 ns, T 2 H = 11.9 ± 0.3 µ s ). Our control scheme is applicable to other color centers and particularly, other group-IV defects for which the scheme may be optimized to improve all-optical control in these systems.