Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session R11: Dopants and Defects in Semiconductors - Quantum InformationFocus
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Sponsoring Units: DMP DQI DCOMP FIAP Chair: Gregory Fuchs, Cornell Univ Room: LACC 303A |
Thursday, March 8, 2018 8:00AM - 8:36AM |
R11.00001: New color centers in diamond for long distance quantum networks Invited Speaker: Nathalie De Leon Color centers in diamond are promising candidates for quantum networks, as they can serve as solid state quantum memories with efficient optical transitions. Prior work has focused on the NV- center in diamond, which exhibits long spin coherence times and has narrow, spin-conserving optical transitions. However, the NV- center is prone to spectral diffusion, and over 97% of emission is in an incoherent phonon side band, severely limiting scalability. Alternatively, SiV- exhibits excellent optical properties, with 70% of its emission in the zero phonon line and a narrow inhomogeneous linewidth. However, SiV- suffers from short spin coherence times, limited by an orbital relaxation rate (T1) of around 40 ns at 5 K. |
Thursday, March 8, 2018 8:36AM - 8:48AM |
R11.00002: Theoretical Studies on the Stability and Positioning of Germanium-Vacancy (GeV) Color Centers in Diamond Rodrick Kuate Defo, Efthimios Kaxiras, Steven Richardson The germanium-vacancy (GeV) in diamond is structurally similar to the silicon-vacancy (SiV) in diamond and it is an optically active color center which has been investigated for applications in quantum information processing and quantum networks.1,2 Recent work shows that when GeV- centers are integrated into nanoscale diamond waveguides, the optical properties far surpass those seen using NV and SiV centers.3 |
Thursday, March 8, 2018 8:48AM - 9:00AM |
R11.00003: Ab initio theory of intersystem crossings in diamond nitrogen-vacancy qubit Adam Gali, Gergo Thiering Dopants in solids are promising candidates for implementations of quantum bits for quantum computing. In particular, the high-spin negatively charged nitrogen-vacancy defect (NV) in diamond has become a leading contender in solid-state quantum information processing. The initialization and readout of the spin is based on the spin-selective decay of the photo-excited electron to the ground state which is mediated by spin-orbit coupling between excited states states and phonons, i.e. intersystem crossing (ISC). |
Thursday, March 8, 2018 9:00AM - 9:12AM |
R11.00004: Yield Improvement of SiV- Color Centers in Diamond via Silicon/Carbon Sequential Implantation Will Hardy, Duncan Lee, Edward Bielejec Color centers in diamond are promising candidate sources of single photons for future optical and electro-optical quantum platforms, as well as sensitive probes of local magnetic field. The silicon-vacancy center defect (SiV-) is of particular interest due to its relative insensitivity to environmental perturbations. Conventional fabrication methods are non-deterministic in location and have low yield. Here, we describe a technique in which silicon and carbon ions are implanted sequentially to increase the number of available vacancies. Preliminary photoluminescence results indicate an enhancement of the SiV- yield of ~ 25 - 140%. Future work to improve the spatial positioning of these defects to tens of nanometers via focused ion beam implantation will be discussed. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. |
Thursday, March 8, 2018 9:12AM - 9:24AM |
R11.00005: Study of surface impurities on nanodiamonds by ELDOR-detected NMR Zaili Peng, Chathuranga Abeywardana, Susumu Takahashi Diamond is a fascinating material, hosting nitrogen-vacancy (NV) defect centers with unique spin and optical properties. Spin coherence and optical stability of NV centers highly depends on paramagnetic impurity contents near the NV centers. Previous studies suggest the existence of several different types of paramagnetic impurities near the surface of diamond. For example, electron paramagnetic resonance (EPR) investigation of mechanically crushed nanodiamonds (NDs) as well as detonation NDs revealed g~2 like signals that are attributed to structural defects and dangling bonds near the diamond surface. In this presentation, we investigate the physical structures of the surface paramagnetic impurities of NDs by resolving the hyperfine coupling of the surface impurities. We employ high-frequency (HF) EPR and HF electron-electron double resonance (ELDOR)-detected NMR spectroscopy for the study. HF ELDOR-detected NMR method is a powerful method to detect the hyperfine coupling with high sensitivity and fine spectral resolution. |
Thursday, March 8, 2018 9:24AM - 9:36AM |
R11.00006: Resonant excitation of a single dichroic vacancy spin in silicon carbide Roland Nagy, Matthias Niethammer, Florian Kaiser, Oney Soykal, Durga Dasari, Nguyen Son, Cristian Bonato, Sang-Yun Lee, J. Wrachtrup, Matthias Widmann Color centers in solid-state hosts are very attractive systems for scalable and integrated nano photonics and quantum information architectures. The ideal system should meet three key features: first, an electron spin coherence time on the order of milliseconds to permit quantum state manipulation and coupling to surrounding nuclear spins; second, a large fraction of photons must be emitted in the zero phonon line to couple different centers to each other via spin-photon entanglement; third, excellent spectral stability. Here, we demonstrate that all three criteria are met by the dichroic vacancy defect center (V1) in 4H-SiC [1]. The V1 center is a S=3/2 spin system with well-separated optical transitions at around 860 nm [2]. We perform resonant optical excitation studies on single V1 centers to explore the ground and excited state level structures. We will also present studies on the spin dynamics under resonant excitation. We note further that no spectral diffusion has been observed. Therefore, our results pave the way for a robust and scalable quantum information platform based on color centers in silicon carbide [3]. [1] R. Nagy et al., arxiv:1707.02715 [2] M. Widmann et al., Nat. Mater. 14, 164 [3] O. O. Soykal et al., Phys. Rev. B 93, 081207(R) (2016) |
Thursday, March 8, 2018 9:36AM - 9:48AM |
R11.00007: Theory of spin polarization of the silicon vacancy center in hexagonal SiC Wenzheng Dong, Sophia Economou Silicon carbide-based defects are promising for quantum communications and for the next generation of quantum sensors, as they feature long coherence times, frequencies at the telecom, and optical and microwave transitions. We analyze the symmetry-adapted many-body wave functions of the V_{Si} in hexagonal SiC and calculate the inter system crossing (ISC) mechanism, enabled by spin-orbital coupling and phonon assisted relaxation. Our results provide a fundamental explanation of the initialization and readout of the silicon vacancy, key processes for quantum sensing and quantum information processing based on this system. |
Thursday, March 8, 2018 9:48AM - 10:00AM |
R11.00008: Optical Absorption and Emission Mechanisms of Single Defects in Hexagonal Boron Nitride Nicholas Jungwirth, Gregory Fuchs Isolated point defects in wide bandgap semiconductors are single photon sources with applications in quantum optics, precision sensing, and quantum information processing technologies. Here we investigate the polarization selection rules of zero-phonon lines (ZPLs) from isolated defects in h-BN and compare our findings with the predictions of a two-level Huang-Rhys model. Our survey, which spans the spectral range ~550-740 nm, reveals that, in disagreement with the two-level model, the absorption and emission dipoles are often misaligned. We relate the dipole misalignment angle (△θ) of a ZPL to its energy shift from the excitation energy (△E) and find that △θ ≈ 0° when △E corresponds to an allowed h-BN phonon frequency and that 0° ≤ △θ ≤ 90° when △E exceeds the maximum allowed h-BN phonon frequency. Consequently, a two-level Huang-Rhys model succeeds at describing one-phonon processes but fails at describing excitations requiring multiple phonons. We propose that direct excitations requiring multiple phonons are inefficient in h-BN and that these ZPLs are excited indirectly via an intermediate electronic state. This hypothesis is corroborated by polarization that indicate a single ZPL may be excited via multiple mechanisms. |
Thursday, March 8, 2018 10:00AM - 10:12AM |
R11.00009: Ge-Vn complexes in silicon: a viable route toward room temperature single atom devices Simona Achilli, Enrico Prati, Takashi Tanii, Nicola Manini, Giovanni Onida Single-atom transistors are the ultimate scaling solution for applications in quantum information. Devices based on conventional dopant atoms (As, P) in silicon can operate only at cryogenic temperature due to shallow |
Thursday, March 8, 2018 10:12AM - 10:24AM |
R11.00010: Towards coupling Bismuth Dopant Spins in Silicon to Superconducting Resonators at 'Clock Transitions’ James O'Sullivan, Christoph Zollitsch, Leonid Abdurakhimov, Gavin Dold, Oscar Kennedy, Eva Dupont-Ferrier, Jarryd Pla, Patrice Bertet, John Morton Spins in nuclear-spin-free solid state systems such as purified 28Si have seen extensive research as candidates for quantum information storage and processing, thanks to their long spin coherence lifetimes [1]. Strongly coupling such spins to a high Q superconducting resonator provides a route to develop microwave quantum memories. Bismuth donor spins can be tuned to so-called ‘clock transitions’, which, due to their insensitivity to magnetic field noise, can have electron spin coherence times as long as 3 seconds [2]. Achieving coupling to such transitions requires resonators which are both magnetic-field resilient, and frequency tuneable. |
Thursday, March 8, 2018 10:24AM - 10:36AM |
R11.00011: Identification and all-optical dynamic nuclear polarization of Si-vacancy related room temperature qubits in SiC Viktor Ivady, Joel Davidsson, Nguyen Son, Takeshi Ohshima, Igor Abrikosov, Adam Gali Point defect quantum bits (qubits) are very promising platform for quantum information processing (QIP) and nanoscale sensor applications. Among the numerous qubit candidates, silicon-vacancy related defects in silicon carbide (SiC) already shown favorable spin properties, demonstrated even at single defect level at room temperature. Furthermore, due to the small zero-field-splitting, O(10 MHz), of the spin-3/2 sublevels of these centers, they are potentially interesting centers for magnetic field angle independent all-optical dynamic nuclear polarization (ODNP) applications. |
Thursday, March 8, 2018 10:36AM - 10:48AM |
R11.00012: Directed Positioning of Subsurface Single-Atom Dopants in Silicon for Quantum Computing Bethany Hudak, Jiaming Song, Hunter Sims, Sokrates Pantelides, Paul Snijders, Andrew Lupini The ability to controllably position single atoms inside a material is a prerequisite for the creation of next generation atomic-scale devices. Advances in aberration correction allow for precise control over the size and position of the electron probe in a scanning transmission electron microscope (STEM). Here we demonstrate for the first time the ability to controllably move and place subsurface bismuth dopants in a silicon crystal at room temperature using STEM. The controllable positioning of Bi dopants is indicated by two findings from our density functional theory calculations: (1) the strain induced by a substitutional Bi dopant allows for Si vacancies to be preferentially created adjacent to the Bi atoms, and (2) there is no significant energy barrier for the Bi atom to hop into these vacancies once they have formed. Using the electron beam, we exploit this vacancy-mediated motion to direct and place Bi dopants below the surface in specific columns within an oriented Si crystal, an important step towards creating a functional quantum device. |
Thursday, March 8, 2018 10:48AM - 11:00AM |
R11.00013: Defects in silicon – old story or new horizons ? Petio Natzkin, Stefan Weichselbaumer, Martin Brandt, Rudolf Gross, Hans Huebl Coherence and relaxation times of defects in silicon have been studied for more than six decades and contributed to the breaktrough of the semiconductors including the the advent of quantum information processing (QIP). |
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