Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session J34: Focus Session: Hybrid Quantum Devices |
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Sponsoring Units: DAMOP Chair: Mohammad Hafezi, University of Maryland, College Park Room: 704 |
Tuesday, March 4, 2014 2:30PM - 3:06PM |
J34.00001: Quantum Hybrid Systems: New Interface between Quantum Optics and Nanoscience Invited Speaker: Mikhail Lukin We will discuss recent developments involving the use of quantum optical techniques in a combination with nanoscale localization of light and atoms inside or near solid-state systems. Specially, realization of quantum optical phase switch operating at a single photon level will be presented. In addition, new applications involving nanoscale magnetic and temperature sensing in living cells will be discussed. [Preview Abstract] |
Tuesday, March 4, 2014 3:06PM - 3:18PM |
J34.00002: Characterization of Spin-Lattice Relaxation Times of Impurity Centers in Diamond with Superconducting Circuits N. Antler, S. Hacohen-Gourgy, D. Toyli, E. Levenson-Falk, A. Jarmola, P. Kehayias, D. Budker, I. Siddiqi We present measurements of the T$_1$ relaxation times of impurity centers in diamond below 4 K obtained with both a nanobridge SQUID magnetometer and a superconducting resonator with an independent broadband excitation line. We show temperature, field and power dependence of the P1 center relaxation times, and discuss how these dependences fit within current models of spin-lattice relaxation and spin diffusion. These measurements are a step toward identifying the dominant spin-lattice relaxation processes in diamond at cryogenic temperatures, and optimizing such solid-state devices for quantum information processing. [Preview Abstract] |
Tuesday, March 4, 2014 3:18PM - 3:30PM |
J34.00003: Fourier space encoding techniques applied to magnetic resonance imaging using NV centers in diamond Yuliya Dovzhenko, Michael S. Grinolds, Marc Warner, Kristiaan De Greve, Lucas Thiel, Ronald L. Walsworth, Amir Yacoby Nitrogen-vacancy (NV) centers in diamond have demonstrated a number of properties that make them viable candidates for detecting nearby external spins with sub-nanometer resolution at ambient conditions. So far, they have been used to image dark electron spins on the diamond surface and resolve few spins[1], as well as detect ensembles of nuclear spins external to the diamond[2, 3]. A promising direction for improving spatial resolution, signal-to-noise ratio, as well as stability of the detector over time is to integrate variable pulsed DC and RF magnetic field gradients on-chip. Spatial information about the target spins can then be obtained by using Fourier imaging techniques[4]. We present preliminary results in depositing silver wires on the diamond surface above the NV center. We flow time-dependent currents through the wires to produce controllable magnitudes of magnetic fields at the NV, which can be used to both address the NV and provide field gradients for imaging techniques. Our approach has the potential to enable highly-resolved nuclear spin imaging. \\[4pt] [1] Grinolds \textit{et al.}, submitted (2013)\\[0pt] [2] Staudacher \textit{et al.}, Science \textbf{339}, 561 (2013)\\[0pt] [3] Mamin \textit{et al.}, Science \textbf{339}, 557 (2013)\\[0pt] [4] Nichol \textit{et al.}, Phys. Rev. X \textbf{3}, 031016 (2013) [Preview Abstract] |
Tuesday, March 4, 2014 3:30PM - 3:42PM |
J34.00004: Coherent Coupling of a Nitrogen Vacancy Center in Diamond to Lattice Strain Kenneth Lee, Preeti Ovartchaiyapong, Bryan Myers, Laetitia Pascal, Gino Graziano, Ania Bleszynski Jayich Nitrogen-vacancy (NV) centers in diamond are a versatile resource in the development of hybrid quantum systems due to their excellent quantum properties and their ability to strongly couple to several external degrees of freedom. Recent theoretical studies indicate that a system composed of single-crystal diamond (SCD) mechanical resonators may be used to form a hybrid quantum network in which an embedded NV spin forms a quantum memory, and the strain-coupled extended phonon modes of the resonator serve as a quantum data bus. However, experimental investigations of the strain interaction with NV centers are prominently lacking. Here, we use high quality SCD cantilevers to quantitatively measure the NV ground state strain sensitivity in directions both parallel and perpendicular to the NV symmetry axis. Furthermore, we demonstrate strain-mediated coherent coupling of the NV spin evolution to the mechanical motion of the resonator. [Preview Abstract] |
Tuesday, March 4, 2014 3:42PM - 3:54PM |
J34.00005: Atomic clock transitions in NV centers in diamond Cecile Grezes, Yuimaru Kubo, Michael Stern, Ignacio Alvizu, Brian Julsgaard, Takashi Umeda, Junichi Isoya, Jeronimo Maze, Vincent Jacques, Klaus Moelmer, Denis Vion, Daniel Esteve, Patrice Bertet Progress towards a spin-ensemble based quantum memory for superconducting qubits has been made over the past few years, involving reversible coherent storage and retrieval of a single microwave photon from a qubit into the spin ensemble [1]. In this experiment, the storage time is however limited to few 100ns by inhomogeneous broadening of the ensemble, and refocusing techniques like Hahn echo have to be applied to benefit from their long coherence times [2]. First experimental results with refocusing will be presented demonstrating the storage and retrieval of a few-photon field into an ensemble of electronic spins (NV centers in diamond) with storage time up to 40$\mu$s. Of particular importance in this adaptation of Hahn echo techniques for quantum memory are so-called `clock transitions' where the spin frequency is insensitive to first order magnetic field fluctuations, leading to longer coherence times [3]. We study the spectrum and coherence time of an ensemble of $^{14}$NV centers, and reveal the existence of three such clock transitions. \\[4pt] [1] Y. Kubo, PRL 107, 220501 (2011).\\[0pt] [2] B. Julsgaard, PRL 110, 250503 (2013).\\[0pt] [3] G. Wolfowicz, Nature Nano 8, 561-564 (2013). [Preview Abstract] |
Tuesday, March 4, 2014 3:54PM - 4:06PM |
J34.00006: Electron Spin Resonance Detected by a Superconducting Qubit Yuimaru Kubo, Igor Diniz, C\'ecile Grezes, Jun-ichi Isoya, Vincent Jacques, Alexia Auffeves, Denis Vion, Daniel Esteve, Patrice Bertet We have realized a highly sensitive electron spin resonance (ESR) spectrometer. We use a superconducting qubit as a single-microwave-photon detector for the microwave signal emitted by the spins. We implement such an ESR spectrometer in a hybrid quantum circuit [1] where an ensemble of electron spins is coherently coupled to a superconducting qubit via a frequency tunable ``quantum bus'' cavity [2,3]. The electron spins are nitrogen-vacancy (NV) centers in a diamond crystal. A very weak excitation microwave pulse is first applied to a spin ensemble, during which the quantum bus cavity is far detuned from the resonance frequency of the spins. Immediately after the excitation pulse, the quantum bus cavity is rapidly tuned at resonance with the spins for a certain time such that the weak excitation is transferred to the cavity. Finally, the excitation in the cavity is swapped to the qubit; then the excited state probability of the qubit is measured. Small values of the magnetization, $\sim$ 15 m$_{\mathrm{B}}$, can be detected out of 10$^{11}$ spins by this spectrometer [4]. [1] Kubo et al., PRL, \textbf{107}, 220501 (2011). [2] Kubo et al., PRA, \textbf{85}, 012333 (2012). [3] Kubo et al., PRL, \textbf{105}, 140502 (2010). [4] Kubo et al., PRB, \textbf{86}, 064514 (2012). [Preview Abstract] |
Tuesday, March 4, 2014 4:06PM - 4:18PM |
J34.00007: CPHASE gate for two distant NV center spins using optical cavity QED Guido Burkard, David D. Awschalom We propose and analyze a controlled-phase (CPHASE) gate for the spins of two nitrogen-vacancy (NV) centers in diamond embedded in a common optical cavity and driven by two off-resonant lasers. In combination with previously shown single-qubit gates, CPHASE allows for arbitrary quantum computations with the NV $|m_s=0\rangle$ and $|m_s=-1\rangle$ ground states. The coupling of the NV center spin to the cavity mode is based upon Raman transitions via the excited states of the NV center and can be controlled with the intensity or the relative phase of the lasers. We find a characteristic laser frequency at which a laser photon is only scattered into the cavity mode if the NV center spin is $|m_s=0\rangle$, and not in the case $|m_s=-1\rangle$. The scattered photon can then be reabsorbed by another selectively driven NV center and give rise to the conditional phase shift required for the CPHASE gate. Selectivity of NV centers within a larger array could be achieved using electrical control of the zero-field splittings or strain engineering in the crystal. We estimate a gate time of below 10 ns, several orders of magnitude shorter than typical NV electron spin coherence times. The separation between the two NV centers is only limited by the extension of the cavity. [Preview Abstract] |
Tuesday, March 4, 2014 4:18PM - 4:30PM |
J34.00008: Entanglement transfer from microwaves to diamond NV centers Angela V. Gomez, Ferney J. Rodriguez, Luis Quiroga Strong candidates to create quantum entangled states in solid-state environments are the nitrogen-vacancy (NV) defect centers in diamond. By the combination of radiation from different wavelength (optical, microwave and radio-frequency), several protocols have been proposed to create entangled states of different NVs. Recently, experimental sources of non-classical microwave radiation have been successfully realized. Here, we consider the entanglement transfer from spatially separated two-mode microwave squeezed (entangled) photons to a pair of NV centers by exploiting the fact that the spin triplet ground state of a NV has a natural splitting with a frequency on the order of GHz (microwave range). We first demonstrate that the transfer process in the simplest case of a single pair of spatially separated NVs is feasible. Moreover, we proceed to extend the previous results to more realistic scenarios where $^{13}$C nuclear spin baths surrounding each NV are included, quantifying the degradation of the entanglement transfer by the dephasing/dissipation effects produced by the nuclear baths. Finally, we address the issue of assessing the possibility of entanglement transfer from the squeezed microwave light to two nuclear spins closely linked to different NV center electrons. [Preview Abstract] |
Tuesday, March 4, 2014 4:30PM - 4:42PM |
J34.00009: Strong coupling of ferromagnetic magnons to a microwave resonator Yutaka Tabuchi, Seiichiro Ishino, Toyofumi Ishikawa, Rekishu Yamazaki, Koji Usami, Yasunobu Nakamura Coherent coupling between paramagnetic spin ensembles and superconducting quantum circuits is now widely studied for quantum memories and microwave-to-optical quantum transducers. Since those applications require strong coupling and sufficiently long coherence time simultaneously, collective excitation (magnon) in yttrium iron garnet (YIG), a typical ferromagnetic insulator, is an alternative promising candidate. The material known to have high spin density (2$\times 10^{21} \mathrm{cm}^{-3}$) and narrow ferromagnetic resonance (FMR) linewidth ($\sim$ 45 kHz at 4.2 K). As a first step towards quantum state transfer from superconducting qubits to YIG magnons, we demonstrate strong selective coupling between a 3D microwave resonator and the uniform magnon mode. In the experiment, we used a YIG sphere with a diameter of 0.75 mm, mounted in a copper resonator and cooled down to 10 mK. We clearly observed the normal mode splitting between the magnon mode and the resonator in the transmission spectrum. It survived even at the weakest power level where the average photon number is below one. The coupling strength, cavity and FMR linewidth were 82 MHz, 2.2 MHz, and 11.5 MHz, respectively. A coupling scheme of a superconducting qubit to the YIG magnons is also discussed. [Preview Abstract] |
Tuesday, March 4, 2014 4:42PM - 4:54PM |
J34.00010: Mechanical driving of nitrogen-vacancy center spins in diamond E.R. MacQuarrie, T.A. Gosavi, N.R. Jungwirth, S.A. Bhave, G.D. Fuchs We demonstrate direct coupling between nitrogen-vacancy (NV) center spins and cavity phonons by driving spin transitions with mechanically-generated harmonic strain, without mediation by a magnetic field. Using a bulk-mode acoustic resonator fabricated from single-crystal diamond, we exert $\sim7$~MPa of non-axial ac stress on the NV centers within the substrate. When we tune the $m_{s}=+1\leftrightarrow m_{s}=-1$ spin state splitting into resonance with a $\sim1$~GHz mechanical mode, we observe a $\Delta m_{s}=\pm2$ spin transition, which is forbidden by the magnetic dipole selection rule. Additionally, we find that the amplitude of the spin signal varies with the spatial periodicity of the stress standing wave, verifying that NV center spins are directly driven by mechanical oscillations. These direct spin-phonon interactions provide a new opportunity for quantum control and enable studies of spin-phonon interactions at the nanoscale. [Preview Abstract] |
Tuesday, March 4, 2014 4:54PM - 5:06PM |
J34.00011: Interfacing rare earth spin ensembles with superconducting circuits S. Probst, A. Tkalcec, D. Rieger, H. Rotzinger, P. Jung, S. W\"unsch, M. Siegel, A.V. Ustinov, P. Bushev Interfacing photonic and solid-state qubits within a hybrid quantum architecture offers a promising route towards large scale distributed quantum computing. Ensembles of optically active rare earth spins embedded in a crystalline matrix are promising candidates for realizing such an interface. Among these, Er ions are distinct from other spin ensembles due to their optical transitions inside the telecom C-band at 1.54 $\mu$m [1]. We report on single photon on-chip ESR spectroscopy of Er spin ensembles strongly coupled to superconducting and non superconducting microwave resonators [2]. The maximum coupling strength was measured to be 45 MHz at 200 ppm, and the minimum linewidth was 4 MHz at 50 ppm Er concentration, respectively. The strong anisotropy of Er:YSO prevents us from reaching the strong coupling regime at low field transitions. However, with crystals of higher symmetry such as YAP, strong coupling can be reached at relatively small magnetic fields of 30 mT at 5 GHz. In addition, we measured T$_2$ of the spins at millikelvins of about 40 $\mu$s. The experiments demonstrate the potential of rare earth ion doped crystals for their application in quantum information processing and communication. [1] Phys. Rev. B 84, 06051 (R) (2011) [2] Phys. Rev. Lett. 110, 157001 (2013) [Preview Abstract] |
Tuesday, March 4, 2014 5:06PM - 5:18PM |
J34.00012: Coherent manipulation of Rydberg states above surfaces at cryogenic temperatures T. Thiele, S. Filipp, J.A. Agner, H.-J. Schmutz, M. Stammeier, A. Wallraff, F. Merkt The integration of atom optics on a chip presents new possibilities for manipulation and readout of atomic internal and external degrees of freedom. In particular, strong fields and field gradients achievable with microstructured electrodes facilitate the manipulation of Rydberg atoms because of their large dipole moments. This is expected to allow for a strong coupling to microwave photons contained in superconducting coplanar resonators. However, the large dipole moment also makes Rydberg atoms susceptible to stray electric fields, which broaden and shift the atomic transitions [1]. We have developed methods to reduce stray fields by reducing surface adsorption and compensating residual fields. Using an external microwave source, we have recorded Rydberg-Rydberg transitions of a 0.5~mm sized ensemble at a mean distance of $250~\mu$m above gold and superconducting chip surfaces at 3~K. Finally, we have observed coherent Rabi oscillations and have extracted information on residual dc and ac fields in the vicinity of the surface. These techniques may be used for coherent chip-based interfaces between Rydberg atoms and microwave photons. \\[4pt] [1] S.D. Hogan, J.A. Agner, F. Merkt, T. Thiele, S. Filipp and A. Wallraff, PRL {\bf 108}, 063004 (2012) [Preview Abstract] |
Tuesday, March 4, 2014 5:18PM - 5:30PM |
J34.00013: Engineering of micron-sized electron trap in a superconducting tuning-fork resonator Ge Yang, David Czaplewski, Leo Ocola, David Schuster Electrons on helium is a unique two-dimensional electron gas system formed at the interface of a quantum liquid (superfluid helium) and vacuum. The motional and spin states of single-electron quantum dots defined on such systems have been proposed for hybrid quantum computing [1,2]. Here, we will present experiments in which an ensemble of electrons are trapped above a tuning fork superconducting resonator and describe their coupling with both the differential and common mode. Next, we will discuss the design of superconducting resonators with a micron-sized trapping area and a reduced number of trapped electrons, and the experimental progress towards a single trapped electron regime.\\[4pt] [1] S. Lyon, Phys. Rev. A. 74, 5 (2006)\\[0pt] [2] D.I. Schuster, et al. Phys. Rev. Lett. 105, 040503 (2010) [Preview Abstract] |
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