Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session H51: Parametric, Novel, & Strong Coupling of Superconducting Circuits |
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Sponsoring Units: GQI Chair: David Schuster , University of Chicago Room: 398 |
Tuesday, March 14, 2017 2:30PM - 3:06PM |
H51.00001: Implementing quantum optics with parametrically driven superconducting circuits Invited Speaker: Jose Aumentado Parametric coupling has received much attention, in part because it forms the core of many low-noise amplifiers in superconducting quantum information experiments. However, parametric coupling in superconducting circuits is, as a general rule, simple to generate and forms the basis of a methodology for interacting microwave fields at different frequencies. In the quantum regime, this has important consequences, allowing relative novices to do experiments in superconducting circuits today that were previously heroic efforts in quantum optics and cavity-QED. In this talk, I'll give an overview of some of our work demonstrating parametric coupling within the context of circuit-QED as well as some of the possibilities this concept creates in our field. [Preview Abstract] |
Tuesday, March 14, 2017 3:06PM - 3:18PM |
H51.00002: Adiabatic two-qubit state preparation in a superconducting qubit system Stefan Filipp, Marc Ganzhorn, Daniel Egger, Andreas Fuhrer, Nikolaj Moll, Peter Mueller, Marco Roth, Sebastian Schmidt The adiabatic transport of a quantum system from an initial eigenstate to its final state while remaining in the instantaneous eigenstate of the driving Hamiltonian can be used for robust state preparation. With control over both qubit frequencies and qubit-qubit couplings this method can be used to drive the system from initially trivial eigenstates of the uncoupled qubits to complex entangled multi-qubit states. In the context of quantum simulation, the final state may encode a non-trivial ground-state of a complex molecule or, in the context of adiabatic quantum computing, the solution to an optimization problem. Here, we present experimental results on a system comprising fixed-frequency superconducting transmon qubits and a tunable coupler to adjust the qubit-qubit coupling via parametric frequency modulation. We realize different types of interaction by adjusting the frequency of the modulation. A slow variation of drive amplitude and phase leads to an adiabatic steering of the system to its final state showing entanglement between the qubits. [Preview Abstract] |
Tuesday, March 14, 2017 3:18PM - 3:30PM |
H51.00003: Parametric coupling and suppression of crosstalk between two superconducting transmon qubits Gengyan Zhang, Andrew Houck It is a challenge in circuit QED architecture to generate on-demand interaction between qubits without introducing unwanted crosstalk. We report on the design and implementation of a tunable coupler between two transmon qubits, whose coupling strength can be tuned to close to zero due to the interference effect. Two-qubit gates can be realized by parametrically modulating the coupler. Experimental results of tunable cross coupling and parametric modulation will be presented. [Preview Abstract] |
Tuesday, March 14, 2017 3:30PM - 3:42PM |
H51.00004: Quantum bath engineering in near-resonance regime Zhaoqi Leng, Gengyan Zhang, Andrei Vrajitoarea, Andrew Houck Quantum bath engineering aims to stabilize entangled qubit states through carefully engineered dissipation and well-chosen drives, as opposed to traditional gate-based approaches. Recent experimental efforts have demonstrated two qubits autonomous entanglement by dispersively coupling them through one or two resonators. Instead of working in the dispersive regime and tracing out the resonator, we bring qubits and a resonator near resonance so their energy levels hybridize into joint eigenstate ladders. Here, we present results of stabilizing an entangled state of two qubits near resonance with a lossy resonator. In addition, we propose a new way of modularize a qubit-resonator system to achieve remote entanglement between two qubits. [Preview Abstract] |
Tuesday, March 14, 2017 3:42PM - 3:54PM |
H51.00005: Universal qubit stabilization with parametric tunable qubit-cavity interaction Yao Lu, Srivatsan Chakram, Nelson Leung, Ravi Naik, Nathan Earnest, Mingwei Wei, Eliot Kapit, Jens Koch, David Schuster Quantum state stabilization provides a promising path to preserving coherence for quantum systems which is crucial to quantum information science. In this talk, we propose a parametric scheme for stabilizing arbitrary single qubit state with a new type of tunable coupler circuit, where the coupling strength between a transmon qubit and a lumped-element resonator is mediated by a superconducting interference device (SQuID). We show that with this device, the static coupling strength can be tuned from less than 15 MHz to more than 250 MHz by tuning the dc flux that threads into the SQuID loop, while a sideband rate of more than 100MHz can be achieved through ac flux tones at the detuning or the summation of the qubit and cavity frequencies. We demonstrate how the universal qubit stabilization scheme is experimentally realized by a proper selection of difference flux tones and voltage drives. [Preview Abstract] |
Tuesday, March 14, 2017 3:54PM - 4:06PM |
H51.00006: Engineering high-order nonlinear dissipation for quantum superconducting circuits S.O. Mundhada, A. Grimm, S. Touzard, S. Shankar, Z.K. Minev, U. Vool, M. Mirrahimi, M.H. Devoret Engineering nonlinear driven-dissipative processes is essential for quantum control. In the case of a harmonic oscillator, nonlinear dissipation can stabilize a decoherence-free manifold, leading to protected quantum information encoding. One possible approach to implement such nonlinear interactions is to combine the nonlinearities provided by Josephson circuits with parametric pump drives. However, it is usually hard to achieve strong nonlinearities while avoiding undesired couplings. Here we propose a scheme to engineer a four-photon drive and dissipation in a harmonic oscillator by cascading experimentally demonstrated two-photon processes. We also report experimental progress towards realization of such a scheme. [Preview Abstract] |
Tuesday, March 14, 2017 4:06PM - 4:18PM |
H51.00007: Engineering the parity of light-matter interaction in superconducting circuits J. Goetz, F. Deppe, P. Eder, M. Fischer, S. Pogorzalek, E. Xie, K.G. Fedorov, A. Marx, R. Gross In physics, parity describes intrinsic symmetries of quantum states and operators, which has manifold applications in the standard model, quantum information and field theory. The latter includes quantum electrodynamics, describing light-matter interaction predominantly with the odd-parity dipole operator because even-parity quadrupole interactions are strongly suppressed. We present a novel technique for the in-situ transformation of the interaction parity in superconducting quantum circuits. By coupling the odd Pauli operator $\sigma_{x}$ to the quadrupole moment and the even operator $\sigma_{z}$ to the dipole moment of a flux qubit, we can precisely engineer the interaction parity with spatially shaped microwave fields. Our highly symmetric sample architecture enables a complete parity inversion and the observation of longitudinal-coupling-induced transparency. By additional engineering the parity of participating quantum states, we can activate quadrupolar transitions similar to those in multielectron atoms. Our work paves the way towards parity based quantum simulation and physical applications based on longitudinal light-matter interaction. [Preview Abstract] |
Tuesday, March 14, 2017 4:18PM - 4:30PM |
H51.00008: Single-photon driven high-order sideband transitions in an ultrastrongly coupled circuit quantum electrodynamics system Tiefu Li, Zhen Chen, Yimin Wang, Lin Tian, Yueyin Qiu, Kunihiro Inomata, Fumiki Yoshihara, Siyuan Han, Franco Nori, Jaw-Shen Tsai, J. Q. You We report the experimental observation of high-order sideband transitions at the single-photon level in a quantum circuit system of a flux qubit ultrastrongly coupled to a coplanar waveguide resonator. With the coupling strength reaching $\mathrm{10\% }$ of the resonator's fundamental frequency, we obtain clear signatures of higher-order red- and first-order blue-sideband transitions. These transitions are owing to the ultrastrong Rabi coupling, instead of the driving power. Our observation advances the understanding of ultrastrongly-coupled systems and paves the way to study high-order processes in the quantum Rabi model. [Preview Abstract] |
Tuesday, March 14, 2017 4:30PM - 4:42PM |
H51.00009: Characteristic spectra of cavity quantum electrodynamics systems from the ultrastrong to the deep strong coupling regime Fumiki Yoshihara, Tomoko Fuse, Kouichi Semba, Sahel Ashhab We have measured spectra of circuit QED systems, where the coupling strength $g$ is much larger than the transition frequency of the qubit $\Delta$ and is around 70\% of the resonance frequency of the oscillator $\omega$. These coupling strengths lie between the ultrastrong [1] and deep strong coupling [2] regimes. We have also performed a systematic analysis of the expected spectra for different values of the coupling strength ranging from the ultrastrong to the deep strong coupling regimes. We show that as the coupling strength increases, the spectrum of a cavity-QED system undergoes multiple qualitative transformations, such that five ranges are identified, each with its own unique spectral features. The spectra in this study, in combination with those of Refs. [1,2], cover four of these five intervals. In all cases the spectral features are consistent with the parameter values extracted from a systematic fitting of the full spectra. These results lead to a quick and simple method for obtaining a rough estimate of the parameter $g/\omega$ simply by looking at the overall features in the spectrum. [1] P. Forn-Diaz et al., PRL 105, 237001 (2010). [2] F. Yoshihara and T. Fuse et al., Nat. Phys. doi.10.1038/NPHYS3906 (2016). [Preview Abstract] |
Tuesday, March 14, 2017 4:42PM - 4:54PM |
H51.00010: Scattering theory in the ultrastrong coupling regime Juan Jose Garcia-Ripoll, Tao Shi, Yue Chang The ultrastrong coupling regime is the one which the light-matter interaction strength is comparable to the energy of the photons and atoms (or qubits) involved. A recent experiment using flux qubits\footnote{P. Forn-Díaz et al, Nature Physics (to appear)} has demonstrated this regime for superconducting circuits and propagating microwave photons, with coupling strengths that go well into the localization phase. In this talk I will present a theoretical framework that can be used to describe the scattering of photons by a two-level system using a combination of the polaron ansatz\footnote{G. Díaz-Camacho et al, Phys. Rev. A 93, 043843 (2016)} and S-matrix formalism\footnote{T. Shi, D.E. Chang, I. Cirac, Phys. Rev. A 92, 053834 (2015)}. This results in quantiative estimates of resonances and lineshapes and can be used to estimate the coupling strength of a dressed artificial atom interacting with a one-dimensional bosonic field. This theoretical approach allows also exploring the potential of the ultrastrong coupling regime for engineering nonlinearities, photon-photon interactions and photon-mediated spin-models. [Preview Abstract] |
Tuesday, March 14, 2017 4:54PM - 5:06PM |
H51.00011: Multi-mode ultra-strong coupling (I): spectroscopic experiments using a vacuum-gap transmon circuit architecture Sal J. Bosman, Mario F. Gely, Vibhor Singh, Alessandro Bruno, Daniel Bothner, Gary A. Steele In circuit QED, multi-mode extensions of the quantum Rabi model suffer from divergence problems. Here, we spectroscopically study multi-mode ultra-strong coupling using a transmon circuit architecture, which provides no clear guidelines on how many modes play a role in the dynamics of the system. As our transmon qubit, we employ a suspended island above the voltage anti-node of a $\lambda/4$ coplanar microwave resonator, thereby realising a circuit where 88\% of the qubit capacitance is formed by a vacuum-gap capacitor with the center conductor of the resonator. We measure vacuum Rabi splitting over multiple modes up to 2 GHz, reaching coupling ratios of $g/\omega=0.18$, well within the ultra-strong coupling regime. We observe a qubit-mediated mode coupling, measurable up to the fifth mode at 38 GHz. Using a novel analytical quantum circuit model of this architecture, which includes all modes without introducing divergencies, we are able to fit the full spectrum and extract a vacuum fluctuations induced Bloch-Siegert shift of up to 62 MHz. This circuit architecture expands the versatility of the transmon technology platform and opens many possibilities in multi-mode physics in the ultra-strong coupling regime. [Preview Abstract] |
Tuesday, March 14, 2017 5:06PM - 5:18PM |
H51.00012: Multi-mode ultra-strong coupling (II): divergence-free multi-mode quantum Rabi model for circuit QED Mario F. Gely, Adrian Parra-Rodríguez, Daniel Bothner, Sal J. Bosman, Enrique Solano, Gary A. Steele In circuit QED, multi-mode extensions of the quantum Rabi model suffer from divergence problems. In circuits that provide no clear guidelines on how many modes play a role in the dynamics of the system, quantitative analysis is challenging due to these divergences. Here, we quantize a lumped element equivalent circuit of the vacuum-gap transmon archicture. As a consequence, the incremental addition of resonator modes renormalizes the qubit frequency and coupling strength, leading to a convergence of the spectrum, even for an infinite number of modes. The resulting multi-mode quantum Rabi Hamiltonian is expressed in terms of the bare qubit and resonator degrees of freedom, thereby retaining the analytical structure of the standard Rabi Hamiltonian. This approach allows us to gain insight into the quantum mechanics of inherently multi-mode circuit QED systems. [Preview Abstract] |
Tuesday, March 14, 2017 5:18PM - 5:30PM |
H51.00013: Unexpectedly allowed transition in two inductively coupled transmons Etienne Dumur, Bruno Kung, Alexey Feofanov, Thomas Weissl, Yuriy Krupko, Nicolas Roch, Cecile Naud, Wiebke Guichard, Olivier Buisson In a transmon qubit the symmetry of the wave functions prevents the direct zero-two transition to occur due to selection rules. In this talk we will present experimental results on a circuit composed of two inductively coupled transmons[1] in which the unexpected direct zero-two transition is observed[2]. Furthermore this transition shows first a magnetic flux dependence and second a clear disappearance at zero magnetic flux. This effect will be discussed through the finite coupling inductance leading to symmetry breaking at non zero magnetic flux. Recently it has been discussed that such transition could produce measurement-induced state transitions in a transmon qubit[3]. \newline [1] E. Dumur, et al, Phys.Rev. B92, 020515(R) (2015). \newline [2] E. Dumur, et al, IEEE Trans. On Appl. Supercond. 26, 1700304 (2016). \newline [3] D. Sank et al, Phys. Rev. Lett. 117, 190503 (2016). [Preview Abstract] |
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