Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session L35: Semiconducting Qubits: Quantum Computing with Defects |
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Sponsoring Units: DQI Chair: Ed Chen, HRL Laboratories Room: BCEC 205B |
Wednesday, March 6, 2019 11:15AM - 11:27AM |
L35.00001: Quantum control and entanglement of 6+ spin qubits in diamond Conor Bradley, Joe Randall, Remon Berrevoets, Mohamed Abobeih, Maarten Degen, Viatcheslav Dobrovitski, Tim Hugo Taminiau The nitrogen vacancy (NV) centre in diamond is a promising candidate for quantum networks. NVs can be entangled remotely [1], and coupling to 13C nuclear spins in the environment provides qubits for the storage and processing of quantum information [2]. In recent years, basic building blocks for a quantum network have been demonstrated, including quantum error correction [2] and entanglement distillation [3]. A key challenge is to realise high-quality control over multiple 13C spin qubits. |
Wednesday, March 6, 2019 11:27AM - 11:39AM |
L35.00002: High-fidelity control of a multi-qubit network node in diamond Joe Randall, Conor Bradley, Remon Berrevoets, Maarten Degen, Mohamed Abobeih, Viatcheslav Dobrovitski, Tim Hugo Taminiau A powerful approach to realise large-scale quantum computations and simulations is to use quantum networks, which are comprised of a number of multi-qubit nodes connected together by photonic links [1]. The nitrogen vacancy (NV) centre in diamond is a promising platform for building such networks, as it combines optical entanglement links through its electron spin [2,3] with long-lived nuclear spin qubits that can store and process quantum information [4,5]. A key requirement is to realise high-fidelity control over multi-qubit nuclear spin registers within each node. |
Wednesday, March 6, 2019 11:39AM - 11:51AM |
L35.00003: Room-Temperature Quantum Error Correction with Nitrogen-Vacancy Centers Mo Chen, David Layden, Paola Cappellaro In pursuit of near-term quantum devices that either demonstrate a `quantum supremacy’ or perform a meaningful algorithm, quantum error correction (QEC) is required. Arguably, fault-tolerance (FT) is not mandatory at this stage. Therefore, instead of traditional FT QEC, we focus on hardware-efficient QEC that demands less redundancy and imposes less overhead penalty. The system of interest is a room-temperature solid-state quantum register consisting of qubits and one ancilla, respectively given by the nuclear spins and the electronic spin associated with the NV center in diamond. |
Wednesday, March 6, 2019 11:51AM - 12:03PM |
L35.00004: Laser Written Diamond Optoelectronic Devices for use in Quantum Computing Yashna Lekhai, Colin Stephen, Yu-Chen Chen, Laiyi Weng, Paul Hill, Sam Johnson, Angelo Frangeskou, Phil Diggle, Michael Strain, Erdan Gu, Ben Green, Mark Newton, Jason M Smith, Patrick Salter, Gavin Morley The nitrogen-vacancy (NV) defect within a diamond lattice has been shown as a viable candidate for a quantum register. Using laser writing, these defect centres can be placed with high precision at any depth through a sample, without inducing significant damage to the surrounding lattice [1-3], to create deep solid state qubit arrays. These sites have shown coherence times of 700 µs, as long as the longest achieved for room-temperature spin-echo coherence measurements in non-12C enriched diamond [1]. Additionally, the technique can be used to create conductive graphitic tracks, which are the subject of current investigation for their potential to act as DC circuitry within the diamond. Configuring the wires such that NVs lie between ends of two wires may allow charge state transfer, bringing greater control of defects, and enable sites to be tuned precisely. It is hoped that, combining these aspects, a single diamond could hold many individually addressable qubits leading to a compact quantum processor. |
Wednesday, March 6, 2019 12:03PM - 12:15PM |
L35.00005: Nitrogen vacancy (NV) centres in diamond for fun and profit Colin Stephen, Sougato Bose, Angelo Frangeskou, ATM Anishur Rahman, Peter F Barker, Laia Gines, Soumen Mandal, Matthew W Dale, Yashna Lekhai, Laiyi Weng, Paul Hill, Sam Johnson, Phil Diggle, Michael Strain, Erdan Gu, Mark Newton, Ben Green, Oliver A Williams, Jason M Smith, Patrick Salter, Gavin Morley We have proposed [1] and begun developing [2-4] an experiment in which a 1 μm diamond containing an NV centre would be put into a superposition of being in two places at once with a superposition distance of 1 μm. This builds on our previous proposals [5-7] and others [8]. |
Wednesday, March 6, 2019 12:15PM - 12:27PM |
L35.00006: Near-term protocols for deterministic photonic graph state generation Antonio Russo, Edwin Barnes, Sophia Economou Highly entangled "graph" states of photons have applications in universal quantum computing and in quantum communications. Here we present near-term experimentally realizable protocols for the deterministic production of graph states, with explicit recipes for nitrogen-vacancy centers in diamond and self-assembled quantum dots. We address the scalability of the approach, focusing on arbitrary size "cluster" states, which can support universal quantum computation. |
Wednesday, March 6, 2019 12:27PM - 12:39PM |
L35.00007: Mechanical driving of nitrogen-vacancy centers in diamond Dominika Lyzwa, Paola Cappellaro
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Wednesday, March 6, 2019 12:39PM - 12:51PM |
L35.00008: Engineering nitrogen-vacancy center electron-phonon coupling with a semi-confocal diamond acoustic resonator Huiyao Chen, Alex Jiang, Noah F Opondo, Sunil Bhave, Gregory Fuchs Diamond-based microelectromechanical systems (MEMS) provide direct coupling between quantum states of nitrogen-vacancy (NV) center and the phonon modes inside the resonator. As a prime example, diamond thin film bulk acoustic resonators (BARs) feature integrated piezoelectric transducer and high-quality factor resonance modes up to the GHz frequency range. The bulk acoustic modes allow mechanical manipulation of deeply imbedded NV centers with long spin/orbital coherence, as recently demonstrated in experiments. Limited by the resonator size, ~100 um, coherent NV electron-phonon interaction is still scarce in current diamond BAR devices. In this talk, we present the design and fabrication of a semi-confocal diamond BAR device with f*Q product >10^{13}. The semi-confocal geometry confines the phonon mode laterally below 10 um. This drastic modal size reduction offers a boost in the NV center electron-phonon coupling with potential applications in spin-mediated resonator cooling and quantum resonator state control. |
Wednesday, March 6, 2019 12:51PM - 1:03PM |
L35.00009: Fabrication of High Quality Quantum Emitters in Diamond Nanostructures Michael Walsh, Eric Bersin, Sara Mouradian, Noel Wan, Dirk R. Englund As the field of solid-state quantum engineering matures, it is increasingly necessary to produce quantum emitters with narrow optical transitions and long spin coherence times aligned to nanophotonic structures. We demonstrate an emitter-device alignment technique enabling fabrication of photonic devices registered to nitrogen-vacancy centers (NVs). The alignment method relies on autonomously imaging emitters and registering them relative to an on-chip coordinate system. This technique can be performed on a large variety of emitters. The repeatability of this method suggests an accuracy down to 50 nm. |
Wednesday, March 6, 2019 1:03PM - 1:15PM |
L35.00010: Spectral stabilization and indistinguishible photon generation by electromechanical tuning of diamond color centers in nanophotonic devices Bartholomeus Machielse, Stefan Bogdanovic, Srujan Meesala, Michael J Burek, Cleaven Chia, Graham Joe, Scarlett Gauthier, Michelle V Chalupnik, Jeffrey Holzgrafe, Linbo Shao, Haig Atikian, Mikhail Lukin, Marko Loncar Silicon-vacancy (SiV) color centers in diamond have excellent optical properties and spin coherence properties, making them ideal candidates for integration into quantum networks. However, their applications are limited by their spectral inhomogeneity and diffusion when implanted within nanophotonic devices. We present a platform for nano-electromechanically stabilizing and tuning the SiV spectral lines inside waveguides and cavities with emitter tuning range 3 times larger than the SiV inhomogeneous distribution. As demonstration of this platform's capabilities, we tune two, waveguide coupled SiV color centers into resonance using strain and generate an entangled superradiant state between them. We demonstrate that this technique can be used for broad bandwidth suppresion of spectral diffusion and to drive spectral lines with 10s of MHz bandwidth. Our platform for cavity coupled, individually tunable solid state quantum emitters with long coherence times should allow for controllable interactions between emitters and is a step towards the creation of a quantum repeater network. |
Wednesday, March 6, 2019 1:15PM - 1:27PM |
L35.00011: Optical Characterization of Single Tin-Vacancy Centers in Diamond Alison Rugar, Shuo Sun, Constantin Dory, Jelena Vuckovic Atom-like defects in diamond have emerged in recent years as candidates for solid-state, optically active qubits. Inversion-symmetric color centers based on group-IV impurities in diamond are of particular interest because of their strong optical properties and relatively good immunity to electric field noise. Phonon-induced transitions resonant with the ground-state (GS) splitting are a major cause of spin decoherence for these color centers but can be mitigated with an increased GS splitting. With a relatively large GS splitting of 850 GHz, the tin-vacancy (SnV) center in diamond holds potential for longer spin coherence times while also possessing good optical properties. In this talk, we will present our recent experimental characterization of the optical and spin properties of single SnV color centers in diamond nanopillars. We measure linewidths <30 GHz, observe a clear polarization dependence of the emission, and experimentally investigate the Zeeman splitting of the SnV. Our results match well the predictions of previous theoretical work. |
Wednesday, March 6, 2019 1:27PM - 1:39PM |
L35.00012: All-electron calculation of spin-spin interactions Krishnendu Ghosh, He Ma, Vikram Gavini, Giulia Galli The decoherence time of defect-spin qubits is controlled by the interaction of nuclear and electronic spins and by that between electronic spins. A key quantity determining these interactions is the value of the electronic spin density at the nucleus, which in turn is a crucial ingredient to evaluate the hyperfine interaction (HF) and zero-field splitting (ZFS) tensors of a defect-spin qubit. Here we report all-electron calculations of the HF and ZFS tensors using real space density functional theory (DFT) calculations based on finite elements. While all-electron DFT calculations using localized basis sets (e.g. Gaussians) can be conveniently performed to determine HF and ZFS tensors of molecules and clusters, they become much more demanding for periodic solids, and plane-wave based calculations are prohibitively difficult to converge. We show that real-space, finite element DFT calculations provide robust estimates of ZFS and HF for both molecules and solids and we present results for molecules and the nitrogen-vacancy center in diamond. We also show that coarse-graining capabilities of the real space mesh included in our formulation enable efficient computations, by avoiding redundant mesh refinements far from the nuclei. |
Wednesday, March 6, 2019 1:39PM - 1:51PM |
L35.00013: Deep-center defects in semiconductors Mariya Romanova, Jelena Sjakste, Nathalie Vast A renewed interest has been recently devoted to the study of deep-center defects in materials for applications in emergent quantum technologies such as quantum sensing. The typical example of a deep-center defect is the nitrogen-vacancy (NV) center in diamond. The spin states of this defect can be optically manipulated at room temperature, which makes it attractive for magnetic sensing [1]. |
Wednesday, March 6, 2019 1:51PM - 2:03PM |
L35.00014: Manipulation of electronic defects in hexagonal boron nitride Elana Urbach, Tamara Sumarac, Helena Knowles, Javier D Sanchez-Yamagishi, Soonwon Choi, Bo Dwyer, Trond I Andersen, Mikhail Lukin Hexagonal boron nitride (hBN) provides a regular nuclear spin lattice, which makes it a promising platform for studying models of spin dynamics. This material also hosts numerous electronic defects that have been well-characterized in bulk electron paramagnetic resonance (EPR) spectroscopy. Nitrogen vacancy (NV) centers in diamond are very sensitive local magnetic field probes that can polarize and control single electronic spins and nanoscale volumes of nuclear spins. In this experiment we use an NV center to manipulate electronic defects in and near hBN, and we are working towards utilizing these defects for better initialization and control of local nuclear spins. |
Wednesday, March 6, 2019 2:03PM - 2:15PM |
L35.00015: Auto-Locking Overhauser Field to the Sweet Point for an Electron Spin by Quantum Weak Measurement of Nuclear Spins Gengli Zhang, Vincent Jacques, Patrice Bertet, Renbao Liu The sweet points such as the clock transitions (CTs) are important for quantum information processing (QIP) and quantum sensing technologies. Being inherently robust to the fluctuations of the environment, they provide almost the best options to counteract the decoherence of the electron spin. The random fields from the environment (Overhauser fields) that lead to the decoherence of the electron spin, however, can also destroy the sweet points, which sets up a big obstacle to the applications. Here we propose a new dynamical nuclear polarization (DNP) scheme that can auto-lock the Overhauser field to the sweet point of the nitrogen vacancy (NV) center. The DNP channel is established by combining the bath state dependent microwave (MW) control, the conditional flipping of the nuclear spins and the optical pumping of the NV center electronic spin. The mechanism can also be understood as sequential weak measurements of the nuclear spins followed by entropy dumping through initialization of the electron spin. |
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