Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session C25: Superconducting Qubits: 3D Architecture |
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Sponsoring Units: GQI Chair: David Schuster, University of Chicago Room: 327 |
Monday, March 18, 2013 2:30PM - 2:42PM |
C25.00001: Approaching 10 Milliseconds for Aluminum Cavities in the Quantum Regime Matthew Reagor, Hanhee Paik, Gianluigi Catelani, Luyan Sun, Christopher Axeline, Teresa Brecht, Jacob Blumoff, Luigi Frunzio, Leonid Glazman, Robert Schoelkopf One of the most promising solid state quantum computing architectures couples superconducting qubits to microwave resonators (circuit QED), a system in which three-dimensional microwave cavities have become a valuable resource. Participation-ratio calculations predict at least four orders of magnitude longer lifetimes in 3D cavities than their planar resonator counterparts with equal material losses. Motivated by this principle, we report multiple superconducting aluminum cavities with lifetimes on the order of 10ms at single photon power and millikelvin temperatures. We also present details on extracting the materials properties and the noise performance of a long lived superconducting cavity resonator, including bounds on the intrinsic dephasing time (T$_{\phi}$) of such a resource. [Preview Abstract] |
Monday, March 18, 2013 2:42PM - 2:54PM |
C25.00002: Materials Effects in 3D-Cavity Transmon Qubits Daniela F. Bogorin, Matthew Ware, Stephen Sorokanich, B.L.T. Plourde Recent experiments have demonstrated significant increases in the coherence of superconducting transmon qubits coupled to three-dimensional microwave cavities. We are investigating the effects of different materials for forming such cavities, as well as various surface treatments of the cavity walls, including electropolishing and electroplating. In addition, we are exploring the influence of the superconducting material that forms the qubit capacitor along with the material that forms the substrate on which the qubit is fabricated. [Preview Abstract] |
Monday, March 18, 2013 2:54PM - 3:06PM |
C25.00003: Coherence of Superconducting Whispering Gallery Resonators Zlatko Minev, Ioan Pop, Dominic Kwok, Michel Devoret Quantum signal processing applications rely on the design of microwave resonators with quality factors at the single photon level exceeding a million. We present a novel on-chip whispering gallery mode resonator formed by two superconducting rings on separate wafers facing each other. The mode energy is principally housed in the lossless vacuum between the rings. We measure internal quality factors of a few million at the single photon level. The superconducting whispering gallery resonator is easily integrable with superconducting qubits. It also constitutes a new tool to characterize thin film material properties. [Preview Abstract] |
Monday, March 18, 2013 3:06PM - 3:18PM |
C25.00004: Deterministic creation of Schrodinger cat states in a superconducting waveguide cavity Brian Vlastakis, Gerhard Kirchmair, Zaki Leghtas, Simon Nigg, Luigi Frunzio, Steven Girvin, Mazyar Mirrahimi, Robert Schoelkopf Off-resonant coupling of a superconducting transmon qubit to a three-dimensional waveguide cavity provides a dispersive qubit/cavity interaction much stronger than any decay rates in the system. Using a two-cavity/single-qubit architecture, we utilize this interaction to deterministically map a qubit state to a superposition of coherent states in a cavity (up to a 40 photon separation). By measuring photon-number parity, we perform Wigner tomography that shows the characteristic interference inherent in quantum superpositions, thus confirming the non-classical properties of the cavity state. Furthermore, we extend this method[1] to create multi-component Schrodinger cat states including the four-component compass state. [1] Z. Leghtas et al. Deterministic protocol for mapping a qubit to coherent state superpositions in a cavity. arXiv.org quant-ph 1208.1603 (2012). [Preview Abstract] |
Monday, March 18, 2013 3:18PM - 3:30PM |
C25.00005: Tunable 3D cQED: Implementation and Characterization Kevin Chou, Matthew Reed, Nissim Ofek, Jacob Blumoff, Brian Vlastakis, Gerhard Kirchmair, Simon Nigg, Luigi Frunzio, Steven Girvin, Robert Schoelkopf Significant progress has recently been made in improving the coherence of superconducting qubits by using the 3D cQED architecture. This current design is static, not allowing for the modulation of couplings and nonlinearities in situ. This limitation may prove to be an obstacle toward scaling this implementation into more complex systems. We present a new architecture which integrates high Q-factor 3D resonators with flux-tunable superconducting transmon qubits. In this talk, we will demonstrate full control over qubit frequency with minimal degradation to qubit and cavity lifetime. This capability allows the rapid and precise control over the system Hamiltonian to choose optimal couplings and nonlinearities as dictated by the experiment. [Preview Abstract] |
Monday, March 18, 2013 3:30PM - 3:42PM |
C25.00006: Tunable 3D cQED: Applications to Quantum Optics and Quantum Information Matthew Reed, Kevin Chou, Nissim Ofek, Jacob Blumoff, Brian Vlastakis, Gerhard Kirchmair, Zaki Leghtas, Simon Nigg, Luigi Frunzio, Steven Girvin, Mazyar Mirrahimi, Robert Schoelkopf The ability to control the frequency of a superconducting qubit on nanosecond timescales has been used, among other things, to generate multi-qubit entanglement. The recently developed 3D cQED architecture has yielded dramatic coherence improvements and novel methods of entangling fixed-tuned qubits, but has until now has lacked the ability to control qubit frequencies in situ. Adding this would grant several abilities. First, the coupling of a qubit to the cavity bus could be modulated to control both the inherited nonlinearity and the dispersive shift of the oscillator. Second, controlling the interactions between individual qubits, particularly those coupled to more than one cavity, could be used to shuttle quantum information between subsystems. Third, a small change to the physical implementation could yield efficient individual qubit QND readout or reset. These abilities are readily applicable to demonstrations of hardware-efficient quantum error correction, entanglement distillation between distant pairs of qubits, and teleportation of quantum information. In this talk, we will discuss our recent results toward achieving these capabilities using the tunable 3D cQED architecture introduced previously. [Preview Abstract] |
Monday, March 18, 2013 3:42PM - 3:54PM |
C25.00007: Extended coherence times of superconducting transmon qubits Erik Lucero, Matthias Steffen, Jay Gambetta, David Abraham, Antonio Corcoles As part of the IBM quantum computing effort, we are building on the pioneering work [1] and recent advances [2] on transmon qubits enclosed in three-dimensional cavities (``3D qubits''). To continue the advance of superconducting qubit architectures for surface code implementations it is clear that we must understand what is limiting coherence times and work to mitigate its effects. By leveraging the reduced fabrication requirements (compared to two-dimensional qubits) and full-device electromagnetic simulation, 3D qubits provide an insightful experimental test-bed to help determine the participation of decoherence mechanisms (e.g. materials, surfaces, radiation) in superconducting qubits. We report on coherence times that go beyond those reported recently [2], making 3D qubits a viable architecture for a prototype quantum processor. [1] Paik, et al., Phys Rev. Lett. 107 240501 [2] Rigetti et al., Phys. Rev. B~86, 100506 [Preview Abstract] |
Monday, March 18, 2013 3:54PM - 4:06PM |
C25.00008: Fluxonium Qubit in a 3D Cavity: Design and Implementation I.M. Pop, K. Geerlings, N. Masluk, A. Kamal, G. Catelani, L. Glazman, M.H. Devoret We describe the implementation of a fluxonium artificial atom [1] with improved coherence times. Our qubit is inductively coupled to a Josephson junction resonator on a sapphire substrate, placed inside a 3D copper cavity. The keystone of the fluxonium qubit is its superinductance, which consists of an array of 90 Josephson junctions. We describe superinductance design improvements [2] which effectively eliminate spurious phase-slips and raise the self-resonant modes of the superinductance well above the frequency of the qubit. Networks of Josephson junctions will be useful for designing custom symmetries in cQED Hamiltonians.\\[4pt] [1] Manucharyan et al., Science, 326 (2009)\\[0pt] [2] Masluk et al., Phys. Rev. Lett. 109 (2012) [Preview Abstract] |
Monday, March 18, 2013 4:06PM - 4:18PM |
C25.00009: Fluxonium Qubit in a 3D Cavity: Measurement and Analysis K. Geerlings, I.M. Pop, N. Masluk, A. Kamal, G. Catelani, L. Glazman, M.H. Devoret We present measurements of a fluxonium qubit [1] in a 3D copper cavity. The fluxonium qubit is composed of a Josephson junction shunted by an array of 90 larger Josephson junctions approximating a linear inductor. In a manner similar to transmon qubits, the coherence times of fluxonium in a 3D cavity have increased when compared to on-chip resonator implementations. Additionally, the fluxonium Hamiltonian can be, by design, less sensitive to decoherence than the transmon. We present measurements of relaxation times for the entire range of flux variation and discuss energy relaxation in light of dielectric, inductive, and quasiparticle losses. \\[4pt] [1] Manucharyan et al., Science, 326 (2009) [Preview Abstract] |
Monday, March 18, 2013 4:18PM - 4:30PM |
C25.00010: A Study of the Multi-Mode Purcell Effect for a Transmon in 3D Circuit QED Andrei Petrenko, Luyan Sun, Jacob Blumoff, Simon Nigg, Steve Girvin, Robert Schoelkopf Although superconducting 3D transmon qubits offer a promising path toward realizing an architecture for quantum computation, they are still limited by decoherence processes that are not yet fully understood. Qubit $T_1$ relaxation due to the Purcell Effect presents one such limitation on coherence times, but thus far a complete model of Purcell processes for transmons in 3D cavities, beyond the approximation of a single cavity mode and lumped element qubit, has been absent. Employing a simple scheme to vary the decay rate $\kappa$ (or quality factor $Q$) of our cavities in-situ we explore in detail how multiple cavity modes contribute to qubit $T_1$ decay in the Purcell regime. In addition, we show the continued dependence of qubit $T_1$ on cavity $\kappa$ as we systematically decouple from our cavity and are no longer Purcell-limited and how this dependence is related to a steady rise in qubit excited state population. Our findings are consistent with theory we have developed based on an effective circuit model for the cavity-qubit system, and set the stage for continuing the study of the multi-mode Purcell Effect by means of in-situ tuning of not just the cavity coupling, but the qubit frequency itself. [Preview Abstract] |
Monday, March 18, 2013 4:30PM - 4:42PM |
C25.00011: Entanglement of two superconducting qubits in a three-dimensional architecture via monochromatic two-photon excitation Stefano Poletto, Jay M. Gambetta, Seth T. Merkel, John A. Smolin, Jerry M. Chow, A.D. Corcoles, D.W. Abraham, Chad Rigetti, Matthias Steffen The superconducting qubit approach for the realization of a quantum processor is a promising candidate because of its compatibility with silicon microfabrication techniques. The coherence times of superconducting devices have continuously improved in the previous decade, with the most noticeably enhancement recently obtained by placing the qubit inside a three-dimensional waveguide cavity. I will present a novel implementation of a two-qubit three dimensional architecture using superconducting qubits, and I will describe a new gate for the direct generation of maximally entangled Bell states. The gate employs the forbidden two-photon 00 - 11 transition, made bright by the interaction between non computational energy levels. A microwave drive tuned to this transition induces Rabi-like oscillations between the ground and doubly excited state via the Bell basis, allowing the generation of entangled states. [Preview Abstract] |
Monday, March 18, 2013 4:42PM - 4:54PM |
C25.00012: Measurement of a three-dimensional circuit QED system with a down-converting parametric amplifier Chad Rigetti, Doug McClure, Lafe Spietz, Jay Gambetta, Stefano Poletto, Erik Lucero, Antonio Corcoles, Jerry Chow, Jim Rozen, Matthias Steffen, Mark Ketchen, Katrina Sliwa, Flavius Shackert, Michael Hatridge, Baleegh Abdo, Michel Devoret We describe measurements of a superconducting transmon qubit in a waveguide cavity with a Josephson Parametric Converter (JPC) operated as a down-converter with gain. The JPC signal mode is matched to the waveguide cavity at approximately 11.2GHz while the amplified signal, taken from the idler port, is roughly an octave lower at 5.5GHz. Operating the system in this down-conversion-with-gain mode makes use of the JPC's capability to act as both a parametric amplifier and a noiseless frequency converter. Further, it decouples the qubit measurement frequency from the functional frequencies of all components following the JPC in the measurement chain. This work thus provides a framework for a turnkey near-quantum-limited measurement chain which can be standardized and optimized over a narrow band without placing constraints on the qubit/cavity system. [Preview Abstract] |
Monday, March 18, 2013 4:54PM - 5:06PM |
C25.00013: Ultra-broadband microwave travelling-wave parametric amplifier for qubit readout Chris Macklin, D.H. Slichter, O. Yaakobi, L. Friedland, V. Bolkhovsky, D.A. Braje, G. Fitch, W.D. Oliver, I. Sidiqi Superconducting parametric amplifiers (paramps) have been used to demonstrate qubit readout approaching the quantum limit in the gigahertz regime. A common limitation of these amplifiers has been relatively small bandwidth due to the use of a resonant nonlinearity. We present measurements of a novel type of paramp based on a superconducting non-linear transmission line. Due to the absence of a resonant structure, these devices achieve useful gain with instantaneous bandwidth approaching 4 GHz. We present detailed measurements of amplifier performance metrics and scattering parameters. Additionally, we have coupled this amplifier to a 3D transmon qubit both directly and via an isolator for comparison. We discuss qubit coherence times and readout performance. This type of amplifier is a strong candidate for an ultra-low-noise following amplifier in frequency-multiplexed qubit readout schemes. [Preview Abstract] |
Monday, March 18, 2013 5:06PM - 5:18PM |
C25.00014: High fidelity all-microwave controlled-phase gate for superconducting qubits by cavity vacuum displacement Hanhee Paik, D. Zhou, M.D. Reed, G. Kirchmair, L. Frunzio, S.M. Girvin, R.J. Schoelkopf We demonstrate a new all-microwave controlled phase entangling gate for the superconducting qubits in the three-dimensional circuit QED (3D cQED) architecture. The gate exploits the strong coupling between qubits and a cavity, wherein the cavity frequency dispersively shifts depending on the qubit register state. We off-resonantly displace the cavity vacuum state; each computational state evolves a different phase due to the dispersive coupling, yielding a conditional phase. While designed to exploit the advantages of the 3D cQED architecture, the gate requires only dispersive coupling, making the gate applicable to a wide variety of superconducting qubit architectures. We demonstrate 98\% gate fidelity evaluated by quantum process tomography, and will discuss how appropriate choices of system parameters could increase this number and how we could minimize the gate infidelity due to measurement induced dephasing and non-adiabatic gate procedure. [Preview Abstract] |
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