Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session T34: Focus Session: Superconducting Qubits: 3D & Resonators |
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Sponsoring Units: GQI Chair: Michael Vissers, National Institute of Standards and Technology Room: 704 |
Thursday, March 6, 2014 11:15AM - 11:51AM |
T34.00001: Single photon Kerr effect in circuit QED Invited Speaker: G. Kirchmair The recent development of a 3D architecture for superconducting circuits has dramatically increased the coherence time of qubits and cavities. This allows us to reach the single-photon Kerr regime in circuit QED, where the interaction strength between individual photons in a waveguide cavity exceeds the loss rate. Here, using a two-cavity/single-qubit system, we engineer an artificial Kerr medium that enters this regime and allows the observation of new quantum effects. We realize a Gedankenexperiment [1] proposed by Yurke and Stoler, in which the collapse and revival of a coherent state can be observed. During this evolution non-classical superpositions of coherent states, i.e. multi-component Schr\"odinger cat states, are formed. We visualize this evolution by measuring the Husimi Q-function and confirm the non-classical properties of these transient states by Wigner tomography.\\[4pt] In collaboration with B. Vlastakis, Departments of Physics and Applied Physics, Yale University; Z. Leghtas, Departments of Physics and Applied Physics, Yale University and INRIA Paris-Rocquencourt, Domaine de Voluceau; S. E. Nigg and H. Paik, Departments of Physics and Applied Physics, Yale University; E. Ginossar, Department of Physics and Advanced Technology Institute, University of Surrey; M. Mirrahimi, INRIA Paris-Rocquencourt, Domaine de Voluceau; L. Frunzio, S. M. Girvin, and R. J. Schoelkopf, Departments of Physics and Applied Physics, Yale University. \\[4pt] [1] ``Observation of quantum state collapse and revival due to the single-photon Kerr effect,'' G. Kirchmair, B. Vlastakis), Z. Leghtas, S. E. Nigg, H. Paik, E. Ginossar, M. Mirrahimi, L.Frunzio, S. M. Girvin \& R. J. Schoelkopf, Nature, 495, 205 (2013) [Preview Abstract] |
Thursday, March 6, 2014 11:51AM - 12:03PM |
T34.00002: Flux qubits in 3D cavities Michael Stern, Yuimaru Kubo, Cecile Grezes, Denis Vion, Daniel Esteve, Patrice Bertet The flux qubitis often considered as a major design for the future of quantum integrated circuits and its properties have triggered intense interest in the last decade. This superconducting circuit behaves as a two-level system, each level being characterized bythe direction of a macroscopic permanent current flowing in the loop of the qubit. The permanent current, typically of the order of several hundreds of nAs, generates a large magnetic dipole, which offers interesting prospects for hybrid quantum circuits. However, the flux qubit suffers from limited and irreproducible lifetimes which partially prevent these potential applications. Recently, a novel architecture where qubits are placed in a three dimensional cavity was introduced for transmon qubit. It was shown that coherence properties can be greatly improved. In this work, we present the first measurements of flux qubits in a three dimensional cavity and show that they can reach long and apparently more reproducible T1. The qubits were formed on a sapphire substrate and were measured by coupling them inductively to an on-chip superconducting resonator embedded in a three dimensional copper cavity. We show that all the measured flux qubits exhibit an intrinsic T1 comprised between 5 and 13 us. [Preview Abstract] |
Thursday, March 6, 2014 12:03PM - 12:15PM |
T34.00003: Thin-film Lumped-Element LC Resonator Coupled to 3D Microwave Cavity C.J. Ballard, R.P. Budoyo, J.B. Hertzberg, K.D. Voigt, J.R. Anderson, C.J. Lobb, F.C. Wellstood Dramatic improvements have recently been obtained in the coherence times of superconducting transmon qubits by placing the devices into a 3D cavity and probing them via the cavity mode [1]. To better characterize the causes of these improvements, we have replaced the transmon in the 3D cavity with isolated lumped-element LC resonators made from thin-film aluminum on silicon or sapphire substrates. We have tested several resonator designs with a range of coupling strengths and detunings from the 6.1 GHz TE101 cavity mode. We can determine the resonator's internal and external quality factors, shifts in both the cavity and the resonator frequencies, the coupling strengths between the resonator and the cavity, and the power dependence of internal loss in the resonator. We compare these data to a circuit model of an LC resonator capacitively coupled to a cavity resonance. \\[4pt] [1] H. Paik et al., PRL 107, 240501 (2011) [Preview Abstract] |
Thursday, March 6, 2014 12:15PM - 12:27PM |
T34.00004: Thermalization of transmon qubits in 3D multi-cavity structures Daniela F. Bogorin, Doug McClure, Matthew Ware, Stephen Sorokanich, B.L.T. Plourde One avenue for dramatically improving coherence times of superconducting transmon qubits involves coupling the qubits to 3D cavities, with current state-of-the-art coherence times in excess of 0.1ms. For larger and more complex 3D structures with architectures containing multiple qubits and cavities, thermalization of the cavity walls and qubit chips becomes increasingly challenging. We are developing copper multi-cavity structures to ensure a good thermal pathway and various approaches for mounting the qubit chips inside for reproducible coherence data. At the same time, for improving the quality factors of the copper cavities by reducing the cavity surface loss, we are pursuing several techniques for polishing the copper surfaces and applying superconducting coatings. [Preview Abstract] |
Thursday, March 6, 2014 12:27PM - 12:39PM |
T34.00005: Excited state population of a 3D transmon in thermal equilibrium X.Y. Jin, S. Gustavsson, A. Kamal, A.P. Sears, T. Gudmundsen, D. Hover, A.J. Kerman, F. Yan, J. Yoder, T.P. Orlando, W.D. Oliver We present a systematic study of the excited state population of a 3D transmon qubit at various temperatures. We experimentally demonstrate that the population of the first excited state follows the Maxwell-Boltzmann distribution in the temperature range of 35-150 mK. For bath temperatures below 35 mK, the excited-state population saturates, with an upper-bound estimate of 0.1\%. The saturation suggests a qubit effective temperature of approximately 35 mK. The Lincoln Laboratory portion of this work was sponsored by the Assistant Secretary of Defense for Research \& Engineering under Air Force Contract number FA8721-05-C-0002. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the United States Government. [Preview Abstract] |
Thursday, March 6, 2014 12:39PM - 12:51PM |
T34.00006: Effect of geometry and magnetic field on the coherence time of 3D transmons Chen Wang, Y. Gao, C. Axline, T. Brecht, L. Frunzio, R.J. Schoelkopf The three-dimensional circuit QED architecture has enabled nearly two orders of magnitude of improvement in the coherence time of transmon qubits over the last couple of years[1]. Continued improvement moving forward relies on a better understanding of the factors limiting coherence of the current generation of transmons. Here we present a systematic study of the energy relaxation time (T$_{\mathrm{1}})$ of transmon qubits coupled to 3D waveguide cavities with various designs of capacitor geometries and its dependence on temperature and external magnetic field. Our measurement and analysis indicate both surface dielectric loss and quasiparticle loss play important roles in limiting T$_{\mathrm{1}}$ of 3D transmons. More interestingly, with certain geometric design we found qubit T$_{\mathrm{1}}$ can be improved by cooling in a small magnetic field. These results suggest more complex interplays of loss mechanisms than was previously appreciated and may have important implications for future design of transmons. [1] H. Paik, et al., Phys. Rev. Lett. 107, 240501 (2011). [Preview Abstract] |
Thursday, March 6, 2014 12:51PM - 1:03PM |
T34.00007: Single-qubit gates in frequency-crowded transmon systems Frank Wilhelm, Daniel J. Egger, Ron Schutjens, Fadi Abu Dagga Superconducting transmon qubits in three-dimensional cavities show coherence longer by an order of magnitude compared to their two-dimensional counterparts. To take advantage of these coherence times while scaling up the number of qubits it is advantageous to address individual qubits which are all coupled to the same 3D cavity fields. The challenge in controlling this system comes from spectral crowding, where the leakage transition of qubits ais close to computational transitions in other qubits . Here, it is shown that fast pulses are possible which address single qubits using two -quadrature control of the pulse envelope, while the derivative removal by adiabatic gate method of Refs. [1] alone only gives marginal improvements over the conventional Gaussian pulse shape. On the other hand, a first -order result using the Magnus expansion gives a fast analytical pulse shape which gives a high -fidelity gate, up to a phase factor on the second qubit. Further numerical analysis corroborates these results and yields to even faster gates, showing that leakage -state anharmonicity is not a fundamental quantum speed limit [2]. We will discuss the prospects of experimental implementation. F. Motzoi et al., Phys. Rev. Lett. 103, 110501 (2009). R. Schutjens et al., arXiv:1306.2279 [Preview Abstract] |
Thursday, March 6, 2014 1:03PM - 1:15PM |
T34.00008: Design and Fabrication of Novel Resonators for Scalable 3D cQED T. Brecht, C. Wang, C. Axline, M. Reagor, M. Hatridge, P. Reinhold, L. Frunzio, R.J. Schoelkopf Experiments in three-dimensional circuit quantum electrodynamics (3D cQED) champion the use of superconducting microwave cavities as a quantum resource. The transmon qubit coupled to a 3D superconducting waveguide cavity [1] has yielded enormous gains in coherence times. Cavity coherence times are now approaching 10 milliseconds at single photon power [2]. By virtue of their low surface-to-volume ratio and concomitant low surface dielectric participation, microwave cavities machined out of bulk pieces of superconducting metal are longer lived than planar resonator geometries in the presence of surface losses. However, issues of reproducibility, assembly, and integration become more challenging as we design systems containing many resonators and many qubits. We present a novel architecture for superconducting resonators that retains the superb coherence of 3D structures while achieving superior scalability and compatibility with planar circuitry and integrated readout electronics.\\[4pt] [1] Paik, et al., Phys Rev Lett 107 240501 (2011)\\[0pt] [2] Reagor, et al., Appl Phys Lett 102 192604 (2013) [Preview Abstract] |
Thursday, March 6, 2014 1:15PM - 1:27PM |
T34.00009: Decoherence and Coupling in 3D Transmons Oliver Dial, Douglas McClure, Stefano Poletto, Jay Gambetta, Hanhee Paik, Matthias Steffen, Chris Lirakis Transmons based on 3D architectures can attain coherence times currently unreachable in 2D systems and can be post-selected based on factors such as coherence times and frequency to construct complex quantum systems. Furthermore, because they are measured in simple, well isolated cavity resonators, they provide an ideal testbed for studying decoherence mechanisms. By developing fast design techniques for creating qubits with targeted cavity couplings and anharmonicities, we design, build, and measure a variety of devices tuned to have different participation ratios for different interfaces within the system. Using these devices we explore the different decoherence mechanisms that dominate single cavity qubits and ``bridge'' qubits that cross between two cavity resonators. We acknowledge support from IARPA under contract W911NF-10-1-0324. [Preview Abstract] |
Thursday, March 6, 2014 1:27PM - 1:39PM |
T34.00010: Generation of entanglement between three superconducting qubits distributed among four waveguide cavity resonators Stefano Poletto, Jay M. Gambetta, Andrew W. Cross, Douglas T. McClure, Oliver Dial, Jerry M. Chow, Chris B. Lirakis, Matthias Steffen The 3D architecture for superconducting qubits enabled long coherence times qubits and the ability to hand-select both qubits and cavities alike for optimal parameter selection. A crucial next step towards larger systems consists of spreading entanglement between qubits sharing different cavities. In this talk we present the experimental generation of entanglement on a 3-qubit/4-cavity three-dimensional superconducting architecture obtained by the implementation of the Resonator Induced Phase (RIP) gate. [Preview Abstract] |
Thursday, March 6, 2014 1:39PM - 1:51PM |
T34.00011: Josephson-junction based circuits for coupling 3D cavity modes Adam Sirois, Manuel Castellanos-Beltran, Michael DeFeo, Leonardo Ranzani, Raymond Simmonds, John Teufel, Jose Aumentado Superconducting three-dimensional cavities provide an electromagnetically isolated (high-Q) platform for superconducting quantum information research. Yet, future quantum technologies will require quantum states to be shared or swapped between nearby cavities -- for example between storage and measurement modes. We discuss strategies for coherently swapping states between cavities using Josephson-junction based coupling elements. [Preview Abstract] |
Thursday, March 6, 2014 1:51PM - 2:03PM |
T34.00012: Non-Markovian Qubit Dynamics in Multimode Superconducting circuit cavities Moein Malekakhlagh, Hakan Tureci, Dmitry Krimer, Matthias Liertzer, Stefan Rotter Circuit QED provides a unique platform to investigate the quantum dynamics of an emitter while it is coupled to a large number of modes of an open multimode superconducting microwave resonator . In this talk, we will use a recently developed Green's function method for open photonic systems [1] to study the dynamics of a superconducting transmon qubit coupled to a long superconducting microwave resonator. Then, we find the crossover between three distinct regimes as the qubit-resonator coupling strength is gradually increased: 1. Overdamped decay with a timescale associated with Purcell modified decay rate 2. Underdamped oscillations with a timescale given by the effective vacuum Rabi frequency 3. Pulsed revivals with a timescale given by the resonator round-trip time [1] arXiv:1306.4787 [quant-ph] [Preview Abstract] |
Thursday, March 6, 2014 2:03PM - 2:15PM |
T34.00013: Circuit quantum electrodynamics with a multi-mode cavity Neereja Sundaresan, Devin Underwood, William Shanks, Hakan Tureci, Andrew Houck In most single-cavity experiments studied using circuit quantum electrodynamics, the quantum dynamics consist of superconducting qubit(s) interacting with the fundamental electromagnetic mode of the cavity. For these cavities, the modes are very widely separated and thus higher modes fall outside the microwave regime, inaccessible using standard experimental setup. In a multi-mode cavity, mode spacing is significantly smaller. Specifically, the multi-mode cavity allows us to access a new type of ultra-strong coupling in which the qubit-cavity coupling can be large compared with the mode spacing. In this regime, pulsed revivals on the timescale of half the cavity round-trip time have been predicted [1]. Here, we report preliminary transmission measurements of 0.7 meter long multi-mode cavities with fundamental frequencies less than 100 MHz and evenly spaced harmonics out to 10 GHz. [1] D. O. Krimer, et al. arXiv:1306.4787 [quant-ph] [Preview Abstract] |
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