Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session R29: Quantum Sensing and Computation with DefectsFocus
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Sponsoring Units: DQI Chair: Audrey Bienfait, University of Chicago Room: BCEC 162A |
Thursday, March 7, 2019 8:00AM - 8:36AM |
R29.00001: Quantum control of spins in silicon carbide with photons and phonons Invited Speaker: David Awschalom There is a growing interest in exploiting the quantum properties of electronic and nuclear spins for the manipulation and storage of quantum information. Here we focus on recent developments in controlling and connecting individual spins in silicon carbide (SiC) using photons and phonons. We find that defect-based electronic states in SiC [1] can be isolated and optically probed at the single spin level with surprisingly long spin coherence times and high-fidelity control within non-isotopically purified, commercial-grade wafers operating at near-telecom wavelengths. Moreover, a detailed study of the defect spin-photon interface yields efficient quantum control in various polytypes along with near-unity electronic and nuclear polarization, highlighting the potential of SiC for photon-mediated entanglement. In addition, we use Gaussian surface acoustic wave resonators to exploit both the piezoelectric and isotropic phonon dispersion properties of SiC to demonstrate Autler-Townes splittings, mechanically driven Rabi oscillations, and explore spin-strain coupling contributions from all mechanical degrees of freedom, including shear [2]. The spatial confinement of phonons is mapped using a synchrotron-based x-ray diffraction real-space microscopy technique with 25 nm spatial resolution [3]. This work expands the versatility of optically and mechanically driven spins in a material with well-developed device and fabrication capabilities and shows promise towards integrating quantum states with hybrid quantum systems for both control and communication. |
Thursday, March 7, 2019 8:36AM - 8:48AM |
R29.00002: Quantum network nodes with silicon-vacancy center and coupled nuclear spins in diamond nanocavities Denis Sukachev, Mihir K Bhaskar, Christian T Nguyen, Ruffin Evans, Bartholomeus Machielse, Hongkun Park, Marko Loncar, Mikhail Lukin We realize quantum-network nodes based on silicon-vacancy color centers in diamond nanocavities coupled to nearby nuclear spins. A high cooperativity SiV-cavity interface and efficient tapered-fiber collection allows for single-shot readout of the SiV electronic spin. With dynamical decoupling sequences, we measure a coherence time of 400μs. We observe coupling to nearby 13C spins and demonstrate coherent control of the SiV-13C register. By using these nuclear spins, we realize a quantum memory exceeding 1ms. Together with our previous work, these results pave the way for quantum computation based on 2D cluster states with more than 10 photons, and quantum communication based on quantum repeaters. |
Thursday, March 7, 2019 8:48AM - 9:00AM |
R29.00003: Resonant optical spin initialization and readout of single silicon vacancies in silicon carbide Oney Soykal, Hunter Banks, Samuel Carter, Thomas Reinecke The silicon mono-vacancy defect in 4H-SiC is a promising candidate for solid-state quantum information processing. Recent high-resolution resonant optical spectroscopy on single defects have shown favorable low temperature optical properties, i.e., two narrow and nearly lifetime-limited optical transitions with no discernable zero-field splitting fluctuations or spectral diffusion. We present a theoretical fine structure model that describes the energy level structure and reveals all intersystem crossing and spin polarization time constants of the V2 defect, shedding light on its optical and spin characteristics. In particular, we show that the silicon mono-vacancy is described well by a four-level optical structure assisted by additional non-radiative transitions leading to rich dynamical spin pumping behavior. Our calculated rates result in an overall fluorescence lifetime of 5.8 ns in good agreement with measurements. Based on this model, we show that initialization fidelities exceeding 99% are theoretically attainable at low resonant laser powers. Further, we describe the differences in optical properties between the cubic and the hexagonal defect sites due to dynamic and pseudo Jahn-Teller effects. |
Thursday, March 7, 2019 9:00AM - 9:12AM |
R29.00004: Fault-Tolerant Quantum Metrology with High-Density Spin Ensembles: Theory Joonhee Choi, Hengyun Zhou, Soonwon Choi, Renate Landig, Helena Knowles, Junichi Isoya, Fedor Jelezko, Shinobu Onoda, Hitoshi Sumiya, Mikhail Lukin One of the most promising routes towards high-sensitivity quantum metrology is to utilize high density spin ensembles. Here, spins are typically periodically manipulated in order to both extend coherence and detect an external signal at a particular frequency. However, spin-spin interactions and on-site disorder may severely limit the coherence time and the achievable sensitivities under such dynamical protocols. In addition, control imperfections pose a significant challenge to the effectiveness of decoupling and sensing sequences. Here, we present a novel formalism for the fault-tolerant design of sensing sequences that simultaneously decouples interactions and suppresses the effects of disorder and imperfect controls, while maximizing sensitivity to an external signal. In addition to the broad applicability to different decoupling and sensing scenarios, this formalism could also serve as a powerful tool for the engineering of Hamiltonians to study many-body physics. |
Thursday, March 7, 2019 9:12AM - 9:24AM |
R29.00005: Fault-Tolerant Quantum Metrology with High-Density Spin Ensembles: Experimental Results Helena Knowles, Hengyun Zhou, Joonhee Choi, Soonwon Choi, Renate Landig, Junichi Isoya, Fedor Jelezko, Shinobu Onoda, Hitoshi Sumiya, Mikhail Lukin High density solid-state spin ensembles have shown great promise as high-sensitivity magnetometers on the nanoscale. However, further increases in sensitivity require techniques to overcome the limits to coherence times imposed by spin-spin interactions. Here, using a dense ensemble of Nitrogen-Vacancy centers in diamond, we experimentally demonstrate fault-tolerant decoupling of spin-spin interactions, achieving a ten-fold enhancement of spin coherence times. This was made possible by introducing novel dynamical decoupling sequences that simultaneously suppress disorder, interactions, and imperfections in controls. We utilize the prolonged coherence time to perform quantum metrology, demonstrating an increase in sensitivity compared to conventional sensing protocols such as the XY-8 sequence. These results thus demonstrate a significant enhancement beyond the interaction limit, crucial for high-sensitivity magnetometers in high-density interacting spin ensembles. |
Thursday, March 7, 2019 9:24AM - 9:36AM |
R29.00006: Multi-qubit registers with solid-state defect centers Eric Bersin, Matthew Trusheim, Kevin Chen, Michael Walsh, Sara Mouradian, Tim Schröder, Dirk R. Englund Medium-scale ensembles of qubits offer a platform for near-term quantum technologies, as well as studies of many-body physics. Atom-like emitters in solids have emerged as promising candidates for this application, with long coherence times, coherent optical transitions, the ability to couple to long-lived nuclear spins for extended storage, and a path towards scalability. A prerequisite for generating such clusters is subdiffraction localization, necessary to achieve strong spin-spin coupling for efficient state transfer and gates operations. |
Thursday, March 7, 2019 9:36AM - 9:48AM |
R29.00007: Toward Single-Spin Imaging with Shallow Diamond Nitrogen-Vacancy Centers Zhiran Zhang, Dolev Bluvstein, Nicolas Ryan Williams, Ania Claire Jayich The negatively charged nitrogen-vacancy (NV−) center in diamond is emerging as a powerful quantum magnetometer. As an atomic size sensor, an NV− center incorporated into a scanning probe microscope has the potential of imaging molecular structure. To achieve the requisite sensitivity and spatial resolution, it is crucial that NV− centers are located within nanometers from the surface; however, the diamond surface is known to reduce the spin coherence and charge stability of NV− centers, compromising the capacity of single-spin sensitivity. Here, we address charge state instability of single shallow NV− centers both under illumination and in the dark [1]. We identify tunneling to a local electron trap as the mechanism for charge ionization in the dark and develop techniques to control and readout the trap charge state. We demonstrate experimental protocols to mitigate the detrimental effects, and we present progress towards imaging single molecules. |
Thursday, March 7, 2019 9:48AM - 10:00AM |
R29.00008: High sensitivity quantum limited electron spin resonance spectroscopy Vishal Ranjan, Sebastian Probst, Bartolo Albanese, Emmanuel Flurin, Jarryd Pla, Denis Vion, Daniel Esteve, Klaus Molmer, John Morton, Patrice Bertet Electron spin resonance (ESR) is a well-established method to analyze paramagnetic species, reaction products and complex molecules in materials science, chemistry and molecular biology. Despite widespread use, the conventional ESR based on the inductive detection method has very limited sensitivity, in part due to the small single spin-photon coupling g. Following recent advances in circuit quantum electrodynamics, we have employed high quality factor superconducting resonators to reduce the mode volume around the spins and operate ESR in so-called Purcell regime [1,2] where a larger g not only leads to a larger signal but also provides a high repetition rate. In particular with a nanometric inductor, we show g/2π of 3 kHz, which together with Josephson parametric amplifier pushes the spin sensitivity to be 10 spins for unit signal to noise ratio per second of averaging. |
Thursday, March 7, 2019 10:00AM - 10:12AM |
R29.00009: Enhanced spin-squeezing using a parametrically-driven cavity Peter Groszkowski, Catherine Leroux, Luke Govia, Aashish Clerk Entangled spin-squeezed states allow the possibility of sensing beyond the standard quantum limit, and have been pursued using a variety of different physical mechanisms. In this talk, we will describe and analyze a new, highly-efficient method for generating spin squeezing that exploits a cavity subject to a two-photon (parametric) drive. Unlike standard methods that use a detuned cavity to induce spin-spin interactions (the “one-axis twist” Hamiltonian), our approach employs a resonant interaction and counterdiabatic driving, leading to a more rapid protocol. Our technique can also achieve true Heisenberg-limited scaling, unlike the standard one-axis twisting approach. We will discuss the main properties of the protocol, and explore its performance in realistic parameter settings. The outlined scheme could be implemented in systems where spin ensembles are coupled to superconducting microwave cavities (e.g. [1]), as well as in systems where spins are strain-coupled to the motion of a nanomechanical resonator (e.g. [2,3]). In both cases, the required resource of a parametric drive is experimentally accessible. |
Thursday, March 7, 2019 10:12AM - 10:24AM |
R29.00010: All-optical cryogenic thermometry based on NV centers in nanodiamonds Masaya Fukami, Christopher G Yale, Paolo Andrich, Xiaoying Liu, Joseph Heremans, Paul F Nealey, David Awschalom Nitrogen vacancy (NV) centers in nanodiamonds (NDs) have been shown to provide an excellent nanometer-scale high-sensitivity thermometry platform. Here we demonstrate a cryogenic-compatible, all-optical thermometry technique based on the emission spectrum of an ensemble of NV centers in NDs that operates from room-temperature to liquid nitrogen temperatures. The sensitivity is found to be slightly improved at cryogenic temperatures, in contrast to the conventional thermometry technique based on the temperature-dependent zero-field splitting of NV centers. We use this all-optical thermometer at T=170 K to measure the surface temperature of a ferromagnetic insulator, yttrium iron garnet (YIG), over tens of microns with the use of an array of NDs on a flexible polydimethylsiloxane (PDMS) sheet, where the YIG is thermally driven by a resistive heater. We directly observe a thermal gradient over micrometers in YIG, indicating that the technique is independent of magnetic noise and microwave resonances. |
Thursday, March 7, 2019 10:24AM - 10:36AM |
R29.00011: Optically coherent NV centers in um-thick etched diamond membranes for quantum applications Maximilian Ruf, Mark IJspeert, Suzanne Van Dam, Matthew Weaver, Nick de Jong, Hans van den Berg, Jasper Flipse, Martin Eschen, Santi Sager La Ganga, Guus Evers, Ronald Hanson Future quantum networks depend on efficient entanglement generation between nodes. Recently, we have generated entanglement between nitrogen-vacancy (NV) center nodes with a success rate of up to 40 Hz. This rate is now limited by the zero-phonon-line emission probability as well as the photon collection efficiency. Embedding a diamond slab containing individually resolvable NV centers between two highly reflective mirrors can address both challenges, benefitting from large Purcell enhancement due to a low optical mode volume. |
Thursday, March 7, 2019 10:36AM - 10:48AM |
R29.00012: CMOS-Integrated Diamond Nitrogen-Vacancy Quantum Sensor Christopher Foy, Mohamed Ibrahim, Donggyu Kim, Matthew Trusheim, Dirk R. Englund, Ruonan Han
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Thursday, March 7, 2019 10:48AM - 11:00AM |
R29.00013: Scanning Nitrogen-Vacancy Center Magnetic Imaging Susanne Baumann, Alec Jenkins, Simon A Meynell, Ania Claire Jayich The NV center is a quantum probe that is sensitive to a variety of fields (magnetic, electric, thermal, strain), can achieve nanoscale spatial resolution, is non-invasive, and can operate over a wide range of temperatures; hence it is an ideal tool for studying novel phases of matter that often emerge only below a critical temperature. Here we use a cryogenic scanning NV magnetometer to probe materials that exhibit nanoscale magnetic phenomena often inaccessible to other experimental tools over a variety of temperatures. |
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