Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session R46: Quantum Optics with Superconducting CircuitsFocus

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Sponsoring Units: GQI Chair: Nicholas Roch, University Grenoble Alpes, Neel Institute, France Room: 393 
Thursday, March 16, 2017 8:00AM  8:36AM 
R46.00001: Manybody quantum optics with superconducting circuits Invited Speaker: Neereja Sundaresan Circuit QED is a versatile experimental platform for building complex quantum systems that realize novel strong lightmatter and many body interactions. Due to drive and dissipation, these circuits are fundamentally open systems and are intrinsically suited for studying nonequilibrium steady state physics. I will share a few recent experiments that capture some of the unique domains accessible with superconducting circuits. In one experiment we realize multimode strong coupling, where a single qubit is simultaneously coupled to a large, but discrete, number of microwave cavity modes, with qubitmode coupling strengths comparable to the free spectral range. In a parallel effort, we strongly couple qubits to an effective 1D photonic bandgap crystal. In this structure, qubitphoton dressed bound states introduce a unique pathway to mediate qubitqubit interactions via the tunable spatial overlap of their respective photonic wavefunctions. I will also present results from a larger system, a onedimensional chain of 72 cavities coupled to qubits, where we coherently drive the system into a nonequilibrium steady state. In this system, we find experimental evidence for a dissipative phase transition. Combining the flexibility offered by circuit design and recent progress in characterizing and understanding quantum systems, these experimental directions are a few of the rich avenues ready for study. [Preview Abstract] 
Thursday, March 16, 2017 8:36AM  8:48AM 
R46.00002: Hybrid phaseFockspace approach to evolution of a driven nonlinear resonator Mostafa Khezri, Alexander N. Korotkov We analyze the quantum evolution of a weakly nonlinear damped resonator driven by a classical pump, as in circuit QED measurement of a superconducting qubit. The resonator nonlinearity is induced by coupling with a qubit and produces a shearing effect that squeezes the state of the resonator field, either increasing or decreasing the qubit measurement fidelity. Using a hybrid phaseFockspace representation for the resonator field within the Gaussianstate approximation, we derive evolution equations for the five parameters of a Gaussian state. Numerical solution of these five equations is much simpler than simulation of the density matrix evolution for the field, while providing good accuracy for the numerical analysis of squeezing. [Preview Abstract] 
Thursday, March 16, 2017 8:48AM  9:00AM 
R46.00003: Microwave photons in a highimpedance Josephson transmission line: dispersion, localization, and interactions. Nicholas Grabon, Roman Kuzmin, YenHsiang Lin, Long Nguyen, Nitish Mehta, Vladimir Manucharyan We have fabricated a "telegraph"type transmission line using a pair of capacitively coupled chains of tightlypacked Josephson tunnel junctions. Each chain contains over 10k junctions. Elastic scattering of microwaves at the two ends of the chain creates a forest of standingwave resonances that we detect in a microwave transmission experiment. Analysis of these resonances reveal a 100fold reduction of the speed of light and a 100fold enhancement of the wave impedance, both effects being due to the high kinetic inductance of the junctions. We further explore the effects of both Josephson nonlinearity and disorder in the junction parameters on the localization and interaction of the photons in our transmission line. Our novel circuit offers multiple intriguing options to explore manybody effects with photons. [Preview Abstract] 
Thursday, March 16, 2017 9:00AM  9:12AM 
R46.00004: Self and Cross Kerr effects in a Josephson junction chain. Wiebke Guichard, Yuriy Krupko, Van Duy Nguyen, Etienne Dumur, Thomas Weissl, Javier PuertasMartinez, Remy Dassonneville, Luca Planat, Denis Basko, Frank Hekking, Cecile Naud, Olivier Buisson, Nicolas Roch We have performed microwave transmission measurements on propagation modes in Josephson junction chains containing several hundreds of junctions. After some preliminary measurements [1] we have done a more systematic measurement in an improved measurementsetup. Some of the chains have been embedded into a microwave strip line, while others have been coupled capacitively to it. The latter configuration enables a study of the internal quality factor of the chain while the first one is more suited to study quantitatively the Kerr effects occurring between different modes in the chain. The experimental dispersion curve fits well the theoretical prediction. We measured the Self and Cross Kerr effects by twotone spectroscopy measurements. We deduce from our measurements the Self and Cross Kerr coefficients for the first 8 modes and compare them to theory. [1] T. Weissl, B. Kueng, E. Dumur, A. K. Feofanov, I. Matei, C. Naud, O. Buisson, F. W. J. Hekking, and W. Guichard Phys. Rev. B 92, 104508 (2015) [Preview Abstract] 
Thursday, March 16, 2017 9:12AM  9:24AM 
R46.00005: Bistability in Josephson Junction array resonator Phani Raja Muppalla ``We present an experimental analysis of the Kerr effect of extended plasma resonances in a 1000 Josephson junction (JJ) chain resonator inside a rectangular waveguide. The Kerr effect manifests itself as a frequency shift that depends linearly on the number of photons in a resonant mode. We study the bistable behavior, using a pump probe scheme on two modes of the JJ array, exploiting the CrossKerr effect in our system. In order to understand the behavior of the bistability we perform continuous time measurements to observe the switching between the two metastable states. We observe a strong dependence of the switching rates on the photon number and the drive frequency.'' [Preview Abstract] 
Thursday, March 16, 2017 9:24AM  9:36AM 
R46.00006: Electromagnetically induced transparency in circuit quantum electrodynamics HsiangSheng Ku, Junling Long, Xian Wu, Russell Lake, Xiu Gu, Yuxi Liu, David Pappas Electromagnetically induced transparency (EIT) is a phenomenon caused by quantum interference between distinct transition paths in a threelevel system. In general, it is difficult to realize EIT in a system of threelevel superconducting quantum circuit, because the decay rates and the Rabi frequency of the driving field do not normally satisfy the conditions for EIT. However, we propose to achieve EIT within a driven circuit quantum electrodynamics (cQED) system by creating polariton states and engineering the decay rates of their levels with the driving field.~ In this talk we present spectroscopic measurements of the polariton states that will enable demonstration of EIT within cQED. [Preview Abstract] 
Thursday, March 16, 2017 9:36AM  9:48AM 
R46.00007: Simultaneous bistability of qubit and resonator in circuit quantum electrodynamics Giovanna Tancredi, Themis Mavrogordatos, Matthew Elliott, Michael Peterer, Andrew Patterson, Joseph Rahamim, Peter Leek, Eran Ginossar, Marzena Szymanska We explore an intermediate nonlinear driving regime in circuit QED for a transmon qubit coupled to a 3D cavity, both theoretically and experimentally. In this regime we demonstrate that the qubit and cavity switch simultaneously between metastable states, consistent with quantum activated dynamics of two quantum oscillators. We measure the cavity lineshape and its developing nonlinear features as the drive power is increased and show that neither a Duffing nor a JaynesCummings model are sufficient to provide a good description of the cavity nonlinearity. A generalized JaynesCummings model, taking into account the first four levels of the transmon, does however capture the observed features remarkably well, including a clear partial coherent cancellation of cavity transmission just below the cavity resonance. [Preview Abstract] 
Thursday, March 16, 2017 9:48AM  10:00AM 
R46.00008: Quantum state tomography of a circuit QED dark state Shavindra Premaratne, Frederick Wellstood, Benjamin Palmer A wide variety of quantum optics phenomena can be observed in circuit QED systems due to the capability to widely vary or tune the system parameters. Here, we carefully engineered the dissipation among three quantum levels of a superconducting Al/AlO$_\mathrm{x}$/Al transmon qubit coupled to a 3D Al microwave cavity and used two steadystate drives to observe multiphoton coherent Raman effects including coherent population trapping \footnote{Novikov \textit{et al.}, Nat. Phys. \textbf{12}, 75 (2016)}. Coherent population trapping involves the formation of a steadystate dark state composed of a coherent superposition of two of the initial states in a lambdasystem. We examined the dark state by performing quantum state tomography and observed the average fidelity of generation to be $>92\%$. We demonstrate that good control of the generated dark state over the Bloch sphere, for the two initial states, can be achieved by changing the relative amplitudes and phases of the drives. [Preview Abstract] 
Thursday, March 16, 2017 10:00AM  10:12AM 
R46.00009: Quantum optics in a high impedance environment Javier Puertas, Nicolas Gheeraert, Yuriy Krupko, Remy Dassonneville, Luca Planat, Farshad Foroughui, Cecile Naud, Wiebke Guichard, Olivier Buisson, Serge Florens, Nicolas Roch, Izak Snyman Understanding light matter interaction remains a key topic in fundamental physics. Its strength is imposed by the fine structure constant, $\alpha$. For most atomic and molecular systems $\alpha=\frac{e^2}{\hbar c 4 \pi \epsilon_o}\simeq 1/137 \ll 1$, giving weak interactions. When dealing with superconducting artificial atoms, $\alpha$ is either proportional to $1/Z_c$ (magnetic coupling) or $Z_c$ (electric coupling), where $Z_c$ is the characteristic impedance of the environment [1]. Recent experiments [2,3] followed the first approach, coupling a flux qubit to a low impedance environment, demonstrating strong interaction ($\alpha \sim 1$). In our work, we reached the large $\alpha$ regime, following a complementary approach: we couple electrically a transmon qubit to an array of 5000 SQUIDs. This metamaterial provides high characteristic impedance ($\sim 3k\Omega$), insitu flux tunability and full control over its dispersion relation. In this new regime, all usual approximations break down and new phenomena such as frequency conversion at the single photon level are expected. [1] Devoret, M. et al. Ann. Phys. (2007) [2] Yoshihara, F. et al., Nat. Phys. (2016) [3] Forn Diaz, P. et al., Nat. Phys. (2016) [Preview Abstract] 
Thursday, March 16, 2017 10:12AM  10:24AM 
R46.00010: Quantum optics with giant artificial atoms in a 1D waveguide Anton Frisk Kockum, G\"oran Johansson, Franco Nori In quantum optics experiments with both natural and artificial atoms, the atoms are usually small enough that they can be approximated as pointlike compared to the wavelength of the electromagnetic radiation they interact with. However, a recent experiment coupling a superconducting transmon qubit to surface acoustic waves shows that a single artificial atom can be coupled to a bosonic field at several points which are wavelengths apart. This concept of a ``giant artificial atom'' could also be realized with a superconducting qubit coupled to a meandering microwave transmission line. In a previous theoretical study, we showed that interference effects due to the positions of the coupling points for a single giant artificial atom give rise to a frequency dependence in the atom's relaxation rate and Lamb shift. In the present work, we study two or more giant artificial atoms coupled to a 1D waveguide in various configurations. We investigate collective decay effects (super and subradiance) and exchange interaction between the atoms, and find striking differences compared to the case of small atoms. [Preview Abstract] 
Thursday, March 16, 2017 10:24AM  10:36AM 
R46.00011: Correlations and entanglement between itinerant microwave photons created in a cascaded decay Simone Gasparinetti, Marek Pechal, JeanClaude Besse, Mintu Mondal, Christopher Eichler, Andreas Wallraff We use a threelevel artificial atom in the ladder configuration as a source of microwave photons of different frequency. Our artificial atom is a transmontype superconducting circuit, driven at the twophoton transition between ground and secondexcited state. The transmon is embedded into a singlepole, doublethrow switch [1] that selectively routes differentfrequency photons into different spatial modes. We characterize the decay process both for continuouswave and pulsed excitation. When the source is driven continuously, intensity crosscorrelations between the two modes exhibit a crossover between strong antibunching and superbunching, typical of cascaded decay, and a more complex pattern as the drive strength becomes comparable to the radiative decay rate. In the pulsed mode, we prepare an arbitrary superposition of the ground and secondexcited state and monitor the spontaneous emission of the source in real time. This scheme allows us to deterministically produce entangled photon pairs, as demonstrated by nonvanishing phase correlations and more generally by joint state tomography of the two itinerant photonic modes. [1] M. Pechal \textit{et al.}, Phys.~Rev.~Appl.~\textbf{6}, 024009 (2016). [Preview Abstract] 
Thursday, March 16, 2017 10:36AM  10:48AM 
R46.00012: Single photon devices in superconducting circuits using an atom in front of a mirror Sankar Raman Sathyamoorthy, GĂ¶ran Johansson In circuit QED, artificial atoms made of superconducting circuits interact with microwave photons routed via superconducting transmission lines. The transmission line acts as a bath to which the atoms are coupled and leads to relaxation among other effects. Terminating the transmission line at one end (by grounding for example) is analogous to having a mirror for the field. This boundary condition can be used to change the local density of states of the field with which the atom interacts, so much so that a particular transition of the atom can be completely decoupled from the transmission line. The ``mirror" can be also made movable by using a SQUID at the terminating point, providing additional degree of freedom. In this talk, we present recent results on how to use these effects to make efficient single photon devices such as photon sources in the microwave regime. [Preview Abstract] 
Thursday, March 16, 2017 10:48AM  11:00AM 
R46.00013: Breaking Time Reversal Symmetry in Superconducting Microwave Cavities Brendan Saxberg, Clai Owens, Aman LaChapelle, Alex Ma, Jon Simon, David Schuster In this talk we present our work towards realizing three dimensional high Q, superconducting cavities to be employed in topological circuit QED lattices. In order to generate these kinds of lattices, we developed timereversal symmetry breaking cavities that require an external magnetic field. We coupled magnon excitations in spheres of the ferrite Yttrium Iron Garnet (YIG) to microwave cavity fields in order to break the degeneracy between modes that precess with different handedness. The YIG sphere only couples strongly (\textasciitilde 1GHz) to cavity modes that precess with the same handedness. We explore the use of type II superconductors with high critical fields and methods of focusing the magnetic field to reduce the degradation of the Q in the presence of a magnetic field. [Preview Abstract] 
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