Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session M39: Focus Session: Superconducting Qubits: Hybrid Systems 
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Sponsoring Units: GQI Room: 213AB 
Wednesday, March 4, 2015 11:15AM  11:51AM 
M39.00001: Towards hybrid quantum devices combining superconducting qubits to a spinensemble multiqubit register Invited Speaker: Cecile Grezes Processing quantum information requires quantummechanical systems with long coherence times and that can be easily coupled together to perform logic operations. We report progress on hybrid quantum devices, in which an ensemble of spins provides a longlived multiqubit register for superconducting qubits. We design a memory protocol able to store and retrieve on demand the state of a large number of qubits in the spin ensemble [1]. Qubit states are written by resonant absorption of a microwave photon in the spin ensemble and read out of the memory by applying Hahn echo refocusing techniques to the spins. In a first experiment, we demonstrate the write step of the protocol by integrating on the same chip a superconducting qubit, a resonator with tunable frequency, and an ensemble of NV center spins in diamond [2]. In a second experiment, we demonstrate an important building block of the read step, which consists in retrieving multiple classical microwave pulses at the few photon level using Hahn echo refocusing techniques [3]. First experimental results will be presented in the direction of combining these two building blocks for retrieving a field in the quantum regime. \\[4pt] [1] B. Julsgaard et al., PRL 110, 250503 (2013).\\[0pt] [2] Y. Kubo et al., PRL 107, 220501 (2011).\\[0pt] [3] C. Grezes et al., PRX 4, 021049 (2014). [Preview Abstract] 
Wednesday, March 4, 2015 11:51AM  12:03PM 
M39.00002: Exploring the Physics of Semiconductor Quantum Dots using Circuit Quantum Electrodynamics Anna Stockklauser, Ville Maisi, Thomas Ihn, Klaus Ensslin, Andreas Wallraff Semiconductor quantum dots and superconducting qubits both possess excitations in the microwave domain for which a wide range of novel approaches to create, store, manipulate and detect individual photons have been developed. A key ingredient are coplanar waveguide resonators in which the field energy of an excitation is distributed over a small mode volume. This feature creates sizable electromagnetic fields at the level of individual microwave photons mediating strong electromagnetic interactions with a variety of quantum systems. In an approach known as circuit quantum electrodynamics (QED) we both probe fundamental quantum optical effects and demonstrate basic features of quantum information processing. In this presentation, I will discuss experiments exploring the physics of semiconductor quantum dots in the context of circuit QED. We investigate the coherent dipole coupling of double dots to microwave photons [1,2] and detect radiation emitted from the dots in inelastic electron tunneling processes. This approach may allow us to explore quantum coherent interfaces between semiconducting and superconducting qubits.\newline [1] T. Frey et al., Phys. Rev. Lett. 108, 046807 (2012)\newline [2] A. Wallraff et al., Phys. Rev. Lett. 111, 249701 (2013)\newline [Preview Abstract] 
Wednesday, March 4, 2015 12:03PM  12:15PM 
M39.00003: Improving the coherence time of a quantum system via a coupling with an unstable system Yuichiro Matsuzaki, Xiaobo Zhu, Kosuke Kakuyanagi, Hiraku Toida, Takaaki ShimoOka, Norikazu Mizuochi, Kae Nemoto, Kouichi Semba, William Munro, Hiroshi Yamaguchi, Shiro Saito One of the promising candidates for the realization of quantum information processing is nitrogenvacancy (NV) center. High controllability of NV centers has been achieved with the current technology, including reliable single qubit operations and quantum nondemolition measurements. However, NV center is affected by dephasing due to magneticfield environmental noise, which limits the coherence time of the quantum states. In this talk, we propose a counterintuitive way to improve the coherence time of an NV center where we use a coupling with an unstable system. If we couple a twolevel system such as a superconducting qubit with a single NV center, then a dark state of the NV center naturally forms after the hybridization. We show that this dark state becomes robust against environmental fluctuations due to the coupling even when the coherence time of the twolevel system is much shorter than that of the NV center. [Preview Abstract] 
Wednesday, March 4, 2015 12:15PM  12:27PM 
M39.00004: Spinqubit inspired architectures for superconducting quantum computing YunPil Shim, Charles Tahan In recent years, the superconducting qubit community has achieved single and twoqubit benchmarked gate fidelities approaching 99.9\%, fast readout with novel superconducting amplifiers, distributed entanglement, and other milestones on the road to faulttolerant quantum information processing. Obviously, this is a field that could use some help from the semiconductor qubit community! Here we present theoretical work on superconducting qubit systems inspired by our experience with semiconductor qubits. We discuss initialization, single and twoqubit gate operations, and measurement schemes for an encoded qubit in a twodimensional architecture. Our results motivate new ways of designing or operating superconducting quantum information processors. [Preview Abstract] 
Wednesday, March 4, 2015 12:27PM  12:39PM 
M39.00005: Superconducting qubits with semiconductor nanowire Josephson junctions K.D. Petersson, T.W. Larsen, F. Kuemmeth, T.S. Jespersen, P. Krogstrup, J. Nyg\aa rd, C.M. Marcus Superconducting transmon qubits are a promising basis for a scalable quantum information processor.\footnote{R. Barends \textit{et al.}, Nature \textbf{508}, 500503 (2014).} The recent development of semiconducting InAs nanowires with \textit{in situ} molecular beam epitaxygrown Al contacts presents new possibilities for building hybrid superconductor/semiconductor devices using precise bottom up fabrication techniques.\footnote{P. Krogstrup \textit{et al.}, Nature Materials, \textit{in press}.} Here, we take advantage of these high quality materials to develop superconducting qubits with superconductornormalsuperconductor Josephson junctions (JJs) where the normal element is an InAs semiconductor nanowire. We have fabricated transmon qubits in which the conventional AlAl$_2$O$_3$Al JJs are replaced by a single gatetunable nanowire JJ. Using spectroscopy to probe the qubit we observe fluctuations in its level splitting with gate voltage that are consistent with universal conductance fluctuations in the nanowire's normal state conductance.\footnote{Y.J. Doh \textit{et al.}, Science \textbf{309}, 272275 (2005).} Our gatetunable nanowire transmons may enable new means of control for large scale qubit architectures and hybrid topological quantum computing schemes. [Preview Abstract] 
Wednesday, March 4, 2015 12:39PM  12:51PM 
M39.00006: Coherent control of a transmon qubit with a nanowirebased Josephson junction T.W. Larsen, K.D. Petersson, F. Kuemmeth, T.S. Jespersen, P. Krogstrup, J. Nyg\aa rd, C.M. Marcus Transmon qubits\footnote{Koch, J. et al. \textit{Phys. Rev. A} \textbf{76}, 042319 (2007)} have taken great leaps towards realizing a quantum processor\footnote{Barends, R. et al. \textit{Nature} \textbf{508}, 500 (2014)}. Here we present measurements on a novel, gateable transmon. By tuning the electron density in a semiconducting nanowire\footnote{Krogstrup, P. et al. \textit{Nature Materials}, In press} Josephson junction\footnote{Doh, Y. J. et al. \textit{Science} \textbf{309}, 272 (2005)} we can control the qubit frequency from $\sim$3~GHz to $\sim$8~GHz. The transmon was embedded into an aluminum coplanar waveguide cavity for readout and qubit control. In the resonant regime we observe strong cavityqubit coupling. In the dispersive regime we demonstrate coherent control on the Bloch sphere. The life and coherence times were measured to $T_2^{*}\! \sim \!2T_1 \!\sim \!1~\mu$s. The coherence time was measured to almost 1$\mu$s. Fast gate operations facilitate zrotations as well as promising fast twoqubit operations in future multiplequbit devices. These measurements open new possibilities for gateable superconducting qubits and promise a plausible system for Majorana hybrid devices. [Preview Abstract] 
Wednesday, March 4, 2015 12:51PM  1:03PM 
M39.00007: Fermion parity measurement and control in Majorana circuit quantum electrodynamics Eran Ginossar, Konstantin Yavilberg, Eytan Grosfeld Combining superconducting qubits with mesoscopic devices that carry topological states of matter may lead to compact and improved qubit devices with properties useful for faulttolerant quantum computation. Recently, a charge qubit device based on a topological superconductor circuit has been introduced where signatures of Majorana fermions could be detected. This device stores quantum information in coherent superpositions of fermion parity states originating from the Majorana fermions, generating a highly isolated qubit whose coherence time could be greatly enhanced. We extended the conventional semiclassical method and obtain analytical derivations in the strong coupling regime of the device to cavity photons. We study the effect of the Majorana fermions on the quantum electrodynamics of the device embedded within an optical cavity and develop protocols to initialise, control and measure the parity states. We show that, remarkably, the parity eigenvalue is revealed via dispersive shifts of the optical cavity in the strong coupling regime and its state can be coherently manipulated via a second order sideband transition. [Preview Abstract] 

M39.00008: ABSTRACT WITHDRAWN 
Wednesday, March 4, 2015 1:15PM  1:27PM 
M39.00009: Photonassisted tunnelling with nonclassical microwaves in hybrid circuit QED systems JeanRen\'e Souquet, Matthew Woolley, Julien Gabelli, Pascal Simon, Aashish Clerk Motivated by recent experiments where superconducting microwave circuits have been coupled to electrons in semiconductor nanostructures [13], we study theoretically the interplay of nonclassical light produced in a cavity with electron transport through a tunnel junction [4]. We demonstrate that this basic lightmatter interaction is naturally characterized by nonpositive definite quasiprobability distributions which are intimately connected to the GlauberSudarshan Pfunction. We further demonstrate that this negative quasiprobability has unequivocal signatures on the differential conductance that should be easily detectable in state of art experiments. This thus turns the tunnel junction into a nontrivial probe of the microwave state. We also discuss the nontrivial backaction of the junction current on the cavity.\\[4pt] [1] T. Frey, P. Leek, M. Beck, A. Blais, T. Ihn, K. Ensslin, and A. Wallraff, Phys Rev Lett 108 046807(2012)\\[0pt] [2] M. Delbecq, V. Schmitt, F. Parmentier, N. Roch, J. Viennot, G. Feve, B. Huard, C. Mora, A. Cottet, and T. Kontos, Phys. Rev. Lett. 107, 256804 (2011)\\[0pt] [3] O. Parlavecchio, C. Altimiras, J.R. Souquet, P. Simon, I. Safi, P. Joyez, D. Vion, P. Roche, D. Est\`eve, F. Portier arXiv:1409.6696\\[0pt] [4] Nature Communications 5, 5562 (2014) [Preview Abstract] 
Wednesday, March 4, 2015 1:27PM  1:39PM 
M39.00010: Novel quantum electrooptic transducer for quantum information processing using superconducting 3D qubits H. Paik, L. S. Bishop, D. T. McClure, S. Filipp, J. M. Gambetta, C. B. Lirakis, C. A. Ryan, J. Schlafer, M. P. da Silva, M. Soltani, M. Patel, Z. Dutton We propose a novel electrooptic system, SQOT (Superconducting Qubit Optical Transducer) [1] which can directly exchange quantum information between optical photons at telecom frequencies and superconducting qubits. Our scheme is to fabricate 3D qubits directly on top of a ultrahigh Q whispering gallery mode optical cavity. The optical cavity is itself made from an electrooptic material such that we obtain a direct microwaveoptical interaction between the qubit and optical mode. In this talk, we present recent progress toward designing and building the SQOT device and address challenges such as fabricating Josephson junctions on the electrooptic material and cryogenic microwave losses and possible solutions. [1] H. Paik, U.S. Patent Submitted (2013) [Preview Abstract] 
Wednesday, March 4, 2015 1:39PM  1:51PM 
M39.00011: Manipulation of nonclassical microwave states using parametric interactions Manuel CastellanosBeltran, Michael DeFeo, Adam Sirois, Leonardo Ranzani, Raymond Simmonds, John Teufel, Jose Aumentado A primary goal for researchers in \textit{quantum optics} has been the generation of exotic quantum states  such as Fock states or superpositions of two coherent states. These states have served well in many basic tests of the foundations of quantum theory and the latter may eventually prove useful for quantum computing, communication, and metrology. One important requirement for the generation and use of these states is their precise control and manipulation. In this respect, cQED is a very versatile tool. In the past decade there have been extensive improvements in the storage and retrieval of quantum states of light in this experimental platform and more recently in the manipulation of those states using parametric interactions. In this talk, I will discuss our progress toward the goal of efficiently generating a superposition of smallamplitude coherent states, as well as their detection. This follows from our attempt/goal to implement an ``onchip'' optical table which utilizes parametric interactions for state preparation and measurement. I will also discuss how we use homodyne tomography to fully characterize the states prepared in our setup. [Preview Abstract] 
Wednesday, March 4, 2015 1:51PM  2:03PM 
M39.00012: Fast control and Floquet state dynamics of a strongly driven superconducting qubit Chunqing Deng, Feiruo Shen, JeanLuc Orgiazzi, Sahel Ashhab, Adrian lupascu Floquet states are quasistationary solutions of the Schrodinger equation with a timeperiodic Hamiltonian. They are the appropriate states for describing the dynamics of a qubit in the strong driving regime, where the rotating wave approximation is no longer valid. We performed experiments on strong driving of a superconducting flux qubit using pulses with subnanosecond duration. We explore driving strength up to 5.0 GHz, largely exceeding the qubit Larmor frequency of 2.2 GHz. Floquet state dynamics is visible in the appearance of fast oscillating components in the qubit evolution in the rotating frame. Using pulse shaping, we also demonstrate the control of adiabatic/nonadiabatic transitions between the Floquet states. The control of the Floquet states is relevant for highfidelity singlequbit operations in the strong driving regime. [Preview Abstract] 
Wednesday, March 4, 2015 2:03PM  2:15PM 
M39.00013: Probing an ensemble of superconducting devices Adam Sears, David Hover, Theodore Gudmundsen, Jonilyn L. Yoder, Archana Kamal, Fei Yan, Simon Gustavsson, Andrew Kerman, William Oliver We present experimental results on a system in which we use a flux qubit to probe an ensemble of weakly coupled superconducting devices. We employ standard qubit metrology techniques to reveal global device properties. In addition, we discuss the connection with engineered environmental decoherence. This work is sponsored by the Assistant Secretary of Defense for Research {\&} Engineering under Air Force Contract FA8721050002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Government. [Preview Abstract] 
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