Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E39: Microwave Photonics with Superconducting Circuits IFocus

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Sponsoring Units: DQI Chair: Aashish Clerk, University of Chicago Room: LACC 501B 
Tuesday, March 6, 2018 8:00AM  8:36AM 
E39.00001: From Superconducting Qubits to Microwave Photonics Invited Speaker: Frederick Strauch This talk will review recent progress in using superconducting circuits, traditionally designed as quantum bits for quantum computation, to generate, manipulate, and measure microwave photons. Particular emphasis will be given to the synthesis of nonclassical quantum states and the nonlinear coupling of highly coherent harmonic oscillator modes. Finally, the frontiers of microwave photonics and their application to multidimensional quantum information processing will be discussed. 
Tuesday, March 6, 2018 8:36AM  9:12AM 
E39.00002: Observation of the PhotonBlockade Breakdown Phase Transition Invited Speaker: Johannes Fink , Peter Domokos Phase transitions, such as the change of liquid water into ice, are prominent features of the complex behavior of systems composed of many particles. Recently, theorists have predicted that a cavity containing only a single strongly coupled atom should transition from opaque to transparent when the input photon flux reaches a critical number [1]. And just as water and ice can coexist at the melting point temperature, the cavity was predicted to be both opaque and transparent close to the critical point, stochastically switching between the two states. This coexistence is a hallmark for a firstorder phase transition. 
Tuesday, March 6, 2018 9:12AM  9:24AM 
E39.00003: Observation of genuine threemode interference produced by higher order spontaneous parametric downconversion C. W. S. Chang , A. Vadiraj , Ibrahim Nsanzineza , Christopher Wilson Parametric processes are well recognized as key elements for various quantum protocols. Advancing to higherorder parametric processes has been an ongoing challenge. In particular, a longsought goal in quantum optics has been thirdorder spontaneous parametric downconversion (SPDC), where photons are directly created in triplets. We report the generation of microwave signals from thirdorder SPDC in a multimode parametric cavity when pumping both a single mode and three coupled modes. By pumping at the triple frequency of a single mode, we observe a phasespace distribution with a nonGaussian profile which shows strong skewness in the quadrature amplitude distribution. By pumping at the sum frequency of three modes, we observe nonzero coskewness between the quadrature amplitudes of the modes. These phasedependent threemode correlations are observed even though the twomode covariance between any two of the three modes is zero. This suggest the existence of a nontrivial threemode continuous variable interference. These types of nonGaussian states have been suggested as a resource enabling universal quantum computation with continuous variables. The multimode states may also be useful for threeparty quantum communication protocols such as quantum secret sharing. 
Tuesday, March 6, 2018 9:24AM  9:36AM 
E39.00004: Remote state preparation with squeezed microwaves Kirill Fedorov , Stefan Pogorzalek , Behdad Ghaffari , Peter Eder , Michael Fischer , Edwar Xie , Achim Marx , Frank Deppe , Rudolf Gross Propagating twomode squeezed (TMS) microwave states enable applications of quantum 
Tuesday, March 6, 2018 9:36AM  9:48AM 
E39.00005: Squeezing in transients for a driven nonlinear resonator Mostafa Khezri , Juan Atalaya , Alexander Korotkov We analyze squeezing of a microwave field transmitted through or reflected from a driven nonlinear resonator, focusing on the transient regime. A new way to characterize squeezing in transients is introduced, based on correlators for two different quadratures, measured at two different time moments. This characteristic is directly related to fluctuations in measurement of superconducting qubits and in other setups involving squeezing. A similar analysis is applicable to the transient regime of a Josephson parametric amplifier. 
Tuesday, March 6, 2018 9:48AM  10:00AM 
E39.00006: Experimental Implementation of Higher Order Nonlinear Processes by Cascading Lower Order Nonlinear Processes Shantanu Mundhada , Alexander Grimm , Jayameenakshi Venkatraman , Zlatko Minev , Steven Touzard , Shyam Shankar , Mazyar Mirrahimi , Michel Devoret Nonlinear processes of order greater than four are gaining importance in quantum electrodynamics. In the case of superconducting circuits, the natural way to get higher order nonlinearities is through the higher order terms in the cosine potential of the Josephson junction. However, the magnitude of such nonlinearities reduces as we go to higher terms in the cosine expansion. Here, we explore another route to obtain higher order nonlinearities via cascading lower order nonlinear processes using a Raman transition. Specifically, we present experimental data demonstrating the cascading of a pair of twophoton conversion processes into a fourphoton conversion process. Such a scheme will be useful in engineering fourphoton drivendissipative operations. 
Tuesday, March 6, 2018 10:00AM  10:12AM 
E39.00007: Dissipative stabilization of nonGaussian entangled states in circuit QED Mikhail Mamaev , Luke Govia , Rakesh Tiwari , Aashish Clerk We analyze a scheme enabling the dissipative preparation and stabilization of entangled Schrodinger cat states in two photonic cavities. Our approach is significantly simpler than previously studied proposals. It requires only linear couplings to a single engineered reservoir (as opposed to nonlinear couplings to two more reservoirs). The remaining ingredients required are purely local: each cavity requires a Kerr interaction, and a local twophoton (i.e.~parametric drive). Our scheme is within the reach of stateoftheart experiments in circuit QED. 
Tuesday, March 6, 2018 10:12AM  10:24AM 
E39.00008: Continuous Variable Quantum Computing in Circuit QED Ingrid Strandberg , Fernando Quijandria , Göran Johansson Continuous variables represent a new paradigm for quantum computing in which quantum information is encoded in the quadratures of an electromagnetic field, as opposed to qubitbased models. This field has recently received a lot of attention, mostly focusing on optical frequencies. To achieve universal quantum computation the generation of field states with negative Wigner function is highly desirable. However, deterministic generation of such states at optical frequencies is an experimental challenge, since the available nonlinear materials allows only for squeezing of incoming Gaussian states, leaving the Wigner function positive. In this work, we consider superconducting circuits, where the strong Josephson junction nonlinearity enables straightforward generation of nonGaussian states. Using quantum trajectory methods, we explore the resonance fluorescence from a driven twolevel atom in a 1D transmission line, with parameters compatible with current circuitQED technology. We report on the parameter regimes resulting in outgoing field states with a negative Wigner function. 
Tuesday, March 6, 2018 10:24AM  10:36AM 
E39.00009: Observation of broadband entanglement in microwave radiation from the dynamical Casimir effect. Ben Schneider , Andreas Bengtsson , IdaMaria Svensson , Thomas Aref , Göran Johansson , Jonas Bylander , Per Delsing A fundamental property of the quantum vacuum is that a timevarying boundary condition for the electromagnetic field can generate photon pairs from the vacuum; this is called the Dynamical Casimir Effect (DCE)^{1}. Quantum theory predicts that these photon pairs are entangled and that the resulting electromagnetic field is in a nonclassical state. We use a SQUID at the end of an open transmission line to realize a magneticfluxtunable boundary condition, and generate wideband DCE radiation^{2} by modulating the magnetic flux. The circuit noise and gain is calibrated by using the same SQUID as a shot noise tunnel junction. After calibration, we measure and analyze the covariance matrix for the DCE radiation at two different frequencies which add up to the pump frequency. We calculate the logarithmic negativity, and show twomode squeezing below the vacuum, indicating entanglement. We furthermore estimate a potentially usable generation rate of 90 megaentangled bits per second (Mebit s^{1}) at the sample, applicable for detection schemes^{3} or to entangle quibits^{4}. 
Tuesday, March 6, 2018 10:36AM  10:48AM 
E39.00010: Microwave propagation and localization in modulated ultralong Josephson junction chains. Nitish Jitendrakumar Mehta , Roman Kuzmin , Nicholas Grabon , Raymond Mencia , Natalia Pankratova , Vladimir Manucharyan A linear homogeneous chain of Josephson tunnel junctions supports TEM wave (microwave) propagation. Furthermore, these waves interact with each other due to the Josephson nonlinearity. We have fabricated ultralong chains containing over 30,000 junctions with lithographicallymodulated junction areas. Thanks to the large Josephson kinetic inductance, the chains have a high wave impedance (about 10 kΩ) and a low speed of light (lower than c/100), yielding wavelength much smaller than the system size. Periodic modulation results in gaps in the spectrum whose position and width can be controlled by fabrication. Such a system realizes intriguing interacting photonic crystals. Random modulation is predicted to result in the frequencydependent Anderson localization of light, which also becomes particularly interesting in the presence of interactions. We report our spectroscopic measurements of modulated chains and discuss the interplay between dispersion, disorder, interaction, and dissipation. We also characterize spatial disorder in nominally homogeneous chains, which is important for understanding reproducible junction fabricaition. 
Tuesday, March 6, 2018 10:48AM  11:00AM 
E39.00011: Quantum optics in circuit quantum electrodynamics with a tunable fourlevel system in the nesting regime Junling Long , HsiangSheng Ku , Xian Wu , Russell Lake , Mustafa Bal , Yuxi Liu , David Pappas Circuit quantum electrodynamics (QED) is a paradise for studying quantum optics in the microwave domain because it offers highly scalable architecture with longlived artificial atoms, high quality resonators, large nonlinearity, and tunability. Although some remarkable quantum optics experiments have been implemented in circuit QED system, more exciting phenomenon and experiments that involve complicated energy levels, such as $\Lambda$type levels and Ntype levels, elude researchers as it is difficult to realize such energy levels. Recently, a tunable fourlevel system in circuit QED [PRL 111, 153601 (2013)] has been realized by driving the qubitcavity system to the nesting regime. We have observed electromagnetically induced transparency (EIT) with all onephoton processes using three energy levels of the fourlevel system [arXiv:1704.08777]. By incorporating the fourth level of that system and EIT, we can explore a rich physics of quantum optics, including giant crossphase modulation and wave mixing. In this talk, we will present our recent progress on demonstrating quantum optics experiment with the fourlevel system in circuit QED. 
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