Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session B24: Open Quantum SystemsFocus

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Sponsoring Units: DAMOP Chair: Barry Sanders Room: BCEC 159 
Monday, March 4, 2019 11:15AM  11:51AM 
B24.00001: Dissipative quantum error correction and application to quantum sensing with trapped ions Invited Speaker: Christine Muschik Quantumenhanced measurements hold the promise to improve highprecision sensing ranging from the definition of time standards to the determination of fundamental constants of nature. However, quantum sensors lose their sensitivity in the presence of noise. To protect them, the use of quantum error correcting codes has been proposed. Trapped ions are an excellent technological platform for both quantum sensing and quantum error correction. Here we present a quantum error correction scheme that harnesses dissipation to stabilize a trappedion qubit. In our approach, alwayson couplings to an engineered environment protect the qubit against spin or phase flips. Our dissipative error correction scheme operates in a fully autonomous manner without the need to perform measurements or feedback operations. We show that the resulting enhanced coherence time translates into a significantly enhanced precision for quantum measurements. Our work constitutes a stepping stone towards the paradigm of selfcorrecting quantum information processing. 
Monday, March 4, 2019 11:51AM  12:03PM 
B24.00002: Analysis of matterwave emission into a structured vacuum Michael Stewart, Joonhyuk Kwon, Dominik Schneble Ultracold atoms in optical lattices realize a tunable open quantum 
Monday, March 4, 2019 12:03PM  12:15PM 
B24.00003: Novel Entanglementpreserving approach for universal dissipation mechanisms in quantum nanophotonics Zihao Chen, Yao Zhou, JungTsung Shen Ubiquitously in quantum nanophotonics, photons may be scattered off system impurities to the reservoir, or absorbed by reservoir degrees of freedom, which manifest as different dissipation mechanisms of scattering loss or material loss. Conventionally, fruitful density matrix approach (DMA) is adopted to study such effects, which averages out reservoir degrees of freedom in the reduced density matrix dynamics. While such an approach can incorporate the information that shuttles back and forth between system and reservoir, it does not preserve photonphoton entanglement in the system or the systemreservoir entanglement. 
Monday, March 4, 2019 12:15PM  12:27PM 
B24.00004: Coherent frequency transfer of optical nonlinearities by feedback control of a nondegenerate optical parametric oscillator Edwin Ng, Tatsuhiro Onodera, Ryotatsu Yanagimoto, Hideo Mabuchi Strong, coherent optical nonlinearities, such as those found in atomcavity QED systems, are key resources for ultralowpower optical information processing. However, such nonlinearities often arise from resonant effects occurring in a narrow band of frequencies, limiting their utility within heterogeneous networks of optical devices. At the same time, optical parametric oscillators (OPOs) are a robust platform for tunable light generation, converting pump light into signal and idler light at potentially vastly different frequencies. Here, we consider a coherent feedback scheme in which a narrowband nonlinear device, modelled as a Kerr cavity, is connected by an optical feedback loop to the signal port of an nondegenerate OPO below threshold. We use the SLH formalism to derive a rigorous inputoutput quantum model for this composite device, and we show by numerical simulation that the nonlinear inputoutput behavior of the Kerr cavity can be transferred to the idler port of the OPO, thus implementing a coherent transfer of the optical nonlinearity from one frequency to another. 
Monday, March 4, 2019 12:27PM  12:39PM 
B24.00005: Efficient Fast Forward Protocol in a Heat Engine Renzo Villazon, Anatoli S Polkovnikov, Anushya Chandran Fast forward protocols can be used to engineer rapid adiabatic processes by dynamically tuning available control parameters. For open systems, constructing local transitionless protocols can be a challenging task since one cannot access the bath degrees of freedom needed to prevent nonadiabatic excitations. We present a local fast forward protocol for a particle in a tunable harmonic potential coupled to a bath of optical phonons, which we treat microscopically without making the standard Markovian or Lindbladian approximations. This protocol can be experimentally realized by dynamically tuning the system's frequency and driving its coupling to the environment with a highfrequency Floquet drive. We show that this protocol effectively implements a rapid isothermal process and apply it to realize a fast heat engine operating near the Carnot efficiency. 
Monday, March 4, 2019 12:39PM  12:51PM 
B24.00006: NonGaussian quantum phenonema in synchronouslypumped optical parametric oscillator Tatsuhiro Onodera, Edwin Ng, Peter McMahon, Alireza Marandi, Hideo Mabuchi The synchronouslypumped optical parametric oscillator (SPOPO) below threshold has been engineered to generate multimode squeezing and entanglement among the various frequency components of the broadband pulses. A natural question to ask is whether new phenomena exist in the abovethreshold regime of the SPOPO. To this end, we have developed a quantum inputoutput model of the SPOPO that is rigorously valid above threshold. In this model, we have found theoretical evidence of rich multimode nonGaussian quantum phenomena such as the generation of multimode cat states, which can be engineered by designing the pump spectrum and dispersion of the SPOPO appropriately. We also showed that, consistent with classical intuition, field enhancement due to the localization of the pulse envelope in time enhances the effective nonlinearity by the (large) number of interacting modes. Because of this enhancement, we speculate that nonGaussian states may be experimentally accessible in the future with nearterm, onchip photonic platforms, such as thinfilm lithium niobate. 
Monday, March 4, 2019 12:51PM  1:03PM 
B24.00007: NonMarkovian dynamics revealed at the bound state in continuum Savannah Garmon, Kenichi Noba, Gonzalo Ordonez, Dvira Segal We propose a methodical approach to controlling and enhancing deviations from exponential decay in quantum and optical systems by exploiting recent progress surrounding another subtle effect: the bound states in continuum, which have been observed in optical waveguide array experiments within this past decade. Specifically, we show that by populating an initial state orthogonal to that of the bound state in continuum, it is possible to engineer system parameters for which the usual exponential decay process is suppressed in favor of inverse power law dynamics and coherent effects that typically would be extremely difficult to detect in experiment. We demonstrate our method using a model based on an optical waveguide array experiment, and further show that the method is robust even in the face of significant detuning from the precise location of the bound state in continuum. 
Monday, March 4, 2019 1:03PM  1:15PM 
B24.00008: TwoPhoton Scattering in USC regime Vanessa Paulisch, Tao Shi, Juan Jose GarciaRipoll In this work we study the scattering of pairs of photons by a twolevel system ultrastrongly coupled to a onedimensional waveguide [1]. We describe this problem using a spinboson model with an Ohmic environment J(ω)=παω. We show that when coupling strength lays is about α≤1, the dynamics is well approximated by a polaron Hamiltonian, under the approximation of a conserved number of excitations. In this regime, we develop analytical predictions for the single and twophoton scattering matrix computed with a Green's function method. These predictions are verified against timeevolved matrixproductstate simulations of propagating wavepackets interacting with a twolevel system, showing the accuracy of the approximation. Our predictions for twophoton scattering can be verified using the scattering tomography techniques from Ref. [2] 
Monday, March 4, 2019 1:15PM  1:27PM 
B24.00009: Bloch state scattering in the Brillouin zone Linda E Reichl, Max Porter, Aaron Barr, Ariel Barr Systems with spaceperiodic Hamiltonians have unique scattering properties, just as timeperiodic ones do. We use WignerEisenbud (reaction matrix) scattering theory to consider a twodimensional scattering system in which one dimension is a periodic lattice and the other is localized in space. The scattering and decay properties can then be described by sets of channels, where sets are indexed by Bloch momenta and channels within sets are indexed by incident waves' quantized kinetic energy parallel to the lattice. In the case where the lattice unit cell has reflection symmetry we find that the lattice can sustain formation of antisymmetric bound states in the continuum. Breaking the unit cell symmetry then causes those bound states to become quasibound and slowly decay. We also find in the lowest energy channel that reflection probability increases when varying Bloch momentum. 
Monday, March 4, 2019 1:27PM  1:39PM 
B24.00010: Emergent Finite Frequency Criticality of DrivenDissipative Correlated Lattice Bosons Orazio Scarlatella, Rosario Fazio, Marco Schiro Critical points and phase transitions are characterized by diverging susceptibilities, reflecting the tendency of the system toward spontaneous symmetry breaking. Equilibrium statistical mechanics bounds these instabilities to occur at zero frequency, giving rise to static order parameters. In this work we argue that a prototype model of correlated drivendissipative lattice bosons, of direct relevance for upcoming generation of circuit QED arrays experiments, exhibits a susceptibility sharply diverging at a finite nonzero frequency, which is an emerging scale set by interactions and nonequilibrium effects. In the brokensymmetry phase the corresponding macroscopic order parameter becomes nonstationary and oscillates in time without damping, thus breaking continuous timetranslational symmetry. Our work, connecting breaking of time translational invariance to divergent finite frequency susceptibilities, which are of direct physical relevance, could potentially be extended to study other timedomain instabilities in nonequilibrium quantum systems, including Floquet time crystals and quantum synchronization. 
Monday, March 4, 2019 1:39PM  1:51PM 
B24.00011: Spectral Decomposition of Green’s Functions of Open Quantum Systems Marco Schiro, Orazio Scarlatella, Aashish Clerk We derive a Lehmannstyle representation of spectral functions of Markovian drivendissipative 
Monday, March 4, 2019 1:51PM  2:03PM 
B24.00012: Coarsegrained master equation is valid for a fast bath and any drive Evgeny Mozgunov We compare three master equations: DaviesLindblad, Redfield, and the recent Coarsegrained competely positive equation[1]. We note that the Redfield equation is valid for a fast bath regardless of the relative strength of the coupling to the system Hamiltonian. The main obstruction to using it is its nonpositivity. We show how an attempt to make Redfield positive results in the Coarsegrained master equation. Our new derivation allows to estimate the error of the resulting completely positive equation. Much like Redfield, this equation is applicable for fast bath even if the system Hamiltonian is driven. We thus present a completely positive open system master equation that is a controlled approximation to true evolution for any timedependence of the system Hamiltonian. The fast bath assumption includes any bath with time correlation function decaying faster than 1/t^{2} which is the case for the Ohmic bath. For Ohmic bath, equation is still applicable up to a large timescale. 
Monday, March 4, 2019 2:03PM  2:15PM 
B24.00013: A solution ansatz for Lindblad master equation with a dynamical system theory approach Gehad Sadiek, Elsayed I. Lashin

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