Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session F26: AMO Quantum Information 
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Sponsoring Units: DQI DAMOP Chair: Gavin Brennen, Macquarie Univ Room: LACC 404A 
Tuesday, March 6, 2018 11:15AM  11:27AM 
F26.00001: Building a Quantum Simulator Using Trapped Ions Christian Marciniak , Harrison Ball , Robert Wolf , Michael Biercuk Quantum simulators are by their nature purpose built devices that allow to simulate the dynamics of a difficult to study quantum (or classical) system by using a more accessible one. I will present the objectives and technical challenges associated with building a quantum simulator for transverse Isingtype Hamiltonians with engineered interaction strengths through the example of our planned experiment: a 2D Coulomb crystal of ^{9}Be^{+} confined in a Penning trap. 
Tuesday, March 6, 2018 11:27AM  11:39AM 
F26.00002: Electric field noise in surface ion traps Crystal Noel , Maya LewinBerlin , Clemens Matthiesen , Stephen Gilbert , Stanley Liu , Hartmut Haeffner

Tuesday, March 6, 2018 11:39AM  11:51AM 
F26.00003: Quantum repeater architecture using twospecies trapped ions Sreraman Muralidharan , Siddhartha Santra , Liang Jiang , Vladimir Malinovsky Two cotrapped species of ions, one of which provides a longlived quantum memory while the other serves as an optical communication qubit with high coupling efficiency, can be used as modules to construct nodes of a quantum repeater network. We propose a minimal architecture for the node design based on iontrap modules with Yb ion as a memory qubit and Ba as the communication qubit. Our design includes quantum circuits that achieve intranode Bell measurements between the iontrap modules to perform entanglementswapping locally within the nodes. Based on the fidelity of the required quantum operations and the currently available coupling efficiencies, we estimate the key generation rates that can be expected using the minimal architecture. We also analyze the dependence of the quantum key distribution rate on various experimental parameters, including coupling efficiency, gate infidelity, operation time and length of the elementary links. 
Tuesday, March 6, 2018 11:51AM  12:03PM 
F26.00004: Experimental realization of random access quantum memory of 105 qubits Nan Jiang , Yunfei Pu , Wei Chang , Chang Li , Sheng Zhang , Luming Duan To realize longdistance quantum communication through the quantum repeater network, it is desirable to have a random access quantum memory with many memory cells to have the capability of storing many qubits. And each qubit can be individually addressed in the memory cells, programmable written into and read out from the memory cell to a flying qubit with location independent access time. Here we report an experiment that realizes a random access quantum memory of 210 individually accessible memory cells in a macroscopic atomic ensemble, which can store at least 105 qubits. As a key enabler for a wide range of applications in quantum repeater, we demonstrate that quantum information can be stored into any neighboring memory cells with high fidelity, and more than one flying optical qubits can be stored into pair of memory cells individually one time and then read out after a programmable time in controllable order with high fidelity. The memory is based on electromagneticallyinduced transparency in a single spatiallymultiplexed ensemble of Rb atoms. 
Tuesday, March 6, 2018 12:03PM  12:15PM 
F26.00005: Experimental Realization of a Multiplexed Quantum Memory of 225 Cells and Entanglement Between 25 Memory Cells Yunfei Pu , Nan Jiang , Yukai Wu , Wei Chang , Chang Li , Luming Duan To realize longdistance quantum communication and quantum network, it is required to have multiplexed quantum memory with many memory cells. Here we report an experiment that realizes a multiplexed DLCZtype quantum memory with 225 individually accessible memory cells in a macroscopic atomic ensemble. As a key element for quantum repeaters, we demonstrate that entanglement with flying optical qubits can be stored into any neighboring memory cells and read out after a programmable time with high fidelity. Experimental realization of a multiplexed quantum memory with many individually accessible memory cells and programmable control of its addressing and readout makes an important step for its application in quantum information technology. We also generate multipartite entanglement between 25 (or 9) individually addressable quantum interfaces in a multiplexed atomic quantum memory array and confirm genuine 22 (or 9) partite entanglement, respectively. Experimental entanglement of a recordhigh number of quantum interfaces makes an important enabling step towards realization of quantum networks, longdistance quantum communication, and multipartite quantum information processing. 
Tuesday, March 6, 2018 12:15PM  12:27PM 
F26.00006: Entanglement and Conservation Laws in ManyBody Systems Moshe Goldstein , Eran Sela How are symmetries, which give rise to conservation laws, manifested by entanglement measures? Similarly to the system Hamiltonian, a subsystem's reduced density matrix is composed of blocks characterized by symmetry quantum numbers, or charge sectors. I will present a geometric method for extracting the contribution of individual charge sectors to a subsystem’s entanglement measures within the replica approach, via threading of appropriate conjugate AharonovBohm fluxes through a multisheeted Riemann surface. 
Tuesday, March 6, 2018 12:27PM  12:39PM 
F26.00007: Highprecision hyperfine interaction characterization by adaptive quantum phase estimation Panyu Hou , Xianzhi Huang , Xiaolong Ouyang , XIn Wang , Wengang Zhang , Xiuying Chang , Luming Duan Nuclear spins in solidstate platforms is one of the promising physical systems for quantum computation and quantum simulation due to its extraordinary coherence time and natural existence. To implement the highfideliy intricate spin control, it is imperative to acquire the complete information of the whole system Hamiltonian. We experimentally characterize the hyperfine interaction between the electron spin of NV center and its weakly coupled nuclear spins provided by the surrounding C13. We take advantage of dynamical decoupling technique and the adaptive quantum phase estimation method to acquire the precise hyperfine parameter efficiently. We achieve highfideliy (>90%) initialization for 6 nuclear spins. A hybrid system consisted of six nuclear spins and one electron spin, provides the possibility to complete the complicated task of quantum computation and quantum simulation. 
Tuesday, March 6, 2018 12:39PM  12:51PM 
F26.00008: Implementation of an ideal phase measurement with continuous, adaptive feedback Leigh Martin , William Livingston , Shay HacohenGourgy , Howard Wiseman , Irfan Siddiqi Although the phase of an electromagnetic wave is at the heart of many algorithms in quantum metrology and communication, it is not a quantum operator in the standard sense. Nonetheless, there exists a canonical phase measurement which is conjugate to amplitude. We use a Josephson parametric amplifier and realtime adaptive measurement to perform an approximate canonical phase measurement on a superposition of zero and one photons. Measurement of single quantum trajectories allows us to independently verify the suppression of amplitude information, which guarantees that the output signal is maximally sensitive to phase. These trajectories also provide a diagnostic for optimizing the feedback system, and reconstructing the resulting measurement basis. Our experimental setup exceeds the efficiency of heterodyne detection, the most efficient technique currently used in the field. 
Tuesday, March 6, 2018 12:51PM  1:03PM 
F26.00009: Quantum theory of an atom in proximity to a superconductor Matthias Le Dall , Igor Diniz , Luis Dias Da Silva , Rogério de Sousa The impact of superconductivity on localized atomic states is important for a wide range of experiments. This includes scanning tunneling microscopy (STM) of atoms at the surface of superconductors, superconductingionchip spectroscopy of Rydberg states, and the role of atomlike centers as a source of noise in superconducting qubits. We present a theory of the proximity effect on manyelectron atoms beyond the classical spin (Shiba) approximation [1]. We demonstrate that the emerging orbitallydegenerate YuShibaRusinov (YSR) subgap bound states are split by the presence of Coulomb repulsion, suggesting a novel interpretation for the peak splittings recently observed in STM measurements. Moreover, we demonstrate that the combination of orbital degeneracy and particle number admixture due to Cooperpair formation opens up many forbidden channels for electric and magnetic transitions. As a result, atoms in proximity to superconductors have much more optical and noise activity than anticipated by simple models. 
Tuesday, March 6, 2018 1:03PM  1:15PM 
F26.00010: Practical Real Time Selection Method for Quantum Communication against Atmospheric Turbulence Wenyuan Wang , Feihu Xu , HoiKwong Lo Quantum key distribution (QKD) allows two parties to share a random key with unconditional security. There has been increasing interest in implementing QKD through freespace, which has been implemented between ground stations, mobile platforms, and even from satellite to ground. However, free space QKD is affected by fluctuations in channel transmittance due to atmospheric turbulence. The adaptive real time selection (ARTS) method, proposed by Vallone et al. (2015), uses a classical probe laser to obtain realtime transmittance information, and postselect only hightransmittance regions for quantum key generation with a threshold on classical signal. However, ARTS is limited to singlephoton model. In this work, we are the first to apply ARTS to practical decoystate BB84, and propose an upper bound for the improvement in key rate, which we show can be closely approached by using an optimized threshold. Finally, we perform numerical simulations to demonstrate the effectiveness of ARTS in decoystate BB84, hence providing an easytoimplement method to greatly increase the performance of practical freespace QKD under turbulence. 
Tuesday, March 6, 2018 1:15PM  1:27PM 
F26.00011: Quantum AntiZeno Effect in Single Trapped Ion Wei Wu , Manchao Zhang , ChunWang Wu , Yi Xie , PingXing Chen We experimentally demonstrate the quantum antiZeno effect in a twolevel system based on a single trapped ion. In the large detuning regime, we show that the transfer from the ground state to the excited state can be remarkably enhanced by the inserted projection measurements with an upper bound of probability 0.5, while the transfer barely occurs in the nonmeasurement case. The inserted measurements in our experiment are realized by the electron shelving technique. Compared to the ideal projection measurement, which makes the quantum state collapse instantaneously, a practical electron shelving process needs a finite time duration for state decoherence. We give a detailed theoretical model to describe the dynamics of the quantum state during the practical measurement process. By numerically fitting the experimental data with this theoretical model, we obtain the required minimum value of this time duration with which the experimental results agree well with the antiZeno effect theoretical model. 
Tuesday, March 6, 2018 1:27PM  1:39PM 
F26.00012: Nanophotonic Quantum Interfaces Based on ^{171}Yb:YVO Jonathan Kindem , John Bartholomew , Jake Rochman , Tian Zhong , Philip Woodburn , Charles Thiel , Rufus Cone , Andrei Faraon Rareearth ion (REI) doped crystals are an attractive platform for solid state quantum lightmatter interfaces due to their long optical and spin coherence times at cryogenic temperatures. Although REIs have weak optical transitions, we can enhance their interaction with light and allow for efficient, scalable quantum interfaces by coupling the ions to nanophotonic cavities. In this work, we assess ^{171}Yb:YVO for use in nanoscale quantum interfaces. ^{171}Yb is unique in that it is the only paramagnetic REI isotope with a nuclear spin ½. This provides the simplest possible level structure that allows for a coherent interface between optical and microwave photons on the electron spin and long term quantum storage on the nuclear spin. We report on coherence properties, lifetimes, and inhomogeneous broadening of the optical and nuclear spin transitions in isotopically purified ^{171}Yb:YVO. We engineer a lambda system and demonstrate alloptical coherent control over the nuclear spin ensemble. We also show coupling of the REI ensemble to photonic crystal nanobeam resonators. We conclude that ^{171}Yb:YVO is a promising material for building efficient nanoscale quantum interfaces such as ensemblebased memories, microwave to optical transducers, and optically addressable single REI qubits. 
Tuesday, March 6, 2018 1:39PM  1:51PM 
F26.00013: Generalized Cat States via Daubechies Wavelet Transform Namrata Shukla , Barry Sanders We introduce a quantum version of Daubechiestransformed states and explore its applications to quantum analogues of classical problems for which Daubechies wavelets are useful. Our states are defined in terms of a quantum Daubechies transform applied to the overcomplete coherentstate basis, and we calculate the corresponding Wigner functions, which are then used to analyze the properties of these states. We investigate recursive application of Daubechies transforms and compare these states to the GottesmanKitaevPreskill comb state. The Daubechies transform is constructed via a weighted sum of Glauber displacement operators followed by a squeezing operator, thereby connecting our Daubechiestransformed states to generalized cat states. The Wigner function patterns are complex and we have developed useful methods for understanding these phasespace patterns. In addition, we identify the quantum limit to how many times the Daubechies transform can be recursively applied. Our work is a foray into a representation that exploits Daubechies transform advantages in the quantum domain. 
Tuesday, March 6, 2018 1:51PM  2:03PM 
F26.00014: The replica calculation of entanglement in random unitary circuit Tianci Zhou , Adam Nahum We systematically study the entanglement growth of quantum chaotic evolution by a random unitary circuit using the replica trick. In the computation, the problem maps to the statistical mechanics of interacting random walks. This picture allows us to understand the deterministic linear growth of various R\'enyi entropies as well as the universal physics of the fluctuations. We find that the growth rate is corrected by the entropy of the random walks. 
Tuesday, March 6, 2018 2:03PM  2:15PM 
F26.00015: Hydrodynamics in random unitary circuits with and without conservation laws Frank Pollmann , Tibor Rakovszky , Curt Von Keyserlingk , Shivaji Sondhi The scrambling of quantum information in closed manybody systems has received considerable recent attention. Two useful measures of scrambling have emerged: the spreading of initiallylocal operators, and the related concept of outoftimeordered correlation functions (OTOCs). We tackle this problem by considering 1D spinchains evolving under random local unitary circuits and prove a number of exact results on the behavior of OTOCs. These results follow from the observation that the spreading of operators in random circuits is described by a ``hydrodynamical’’ equation of motion. Moreover, we also consider local random unitary circuits that explicitly conserve a U(1) charge and argue, with numerical and analytical evidence, that the presence of a conservation law slows relaxation in both time ordered and timeoutof ordered correlation functions. We conjecture that the hydrodynamical description applies to more generic ergodic systems and support this numerically. 
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