Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session G7: Entanglement |
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Chair: Winnifred Hensinger, University of Sussex Room: Delaware CD |
Wednesday, June 10, 2015 8:00AM - 8:12AM |
G7.00001: Remote entanglement of ions in parabolic mirror traps Chen-Kuan Chou, Thomas Noel, Carolyn Auchter, Boris Blinov We study ion-photon and remote ion entanglement protocols in application to quantum computation and information. One of the challenges is the efficient coupling between ions and resonant photons. We describe operation of an RF ion trap, which uses a reflective parabolic surface as one of the trap electrodes. This parabolic mirror covers a solid angle of 2-pi sr. around the trapped ion, and the ion can be placed precisely at the focus of the parabola. We measure approximately 40{\%} fluorescence collection from a single barium ion with this setup, with the image spot size of about twice the diffraction limit. Using a reflective fiber collimator for the collected photos, we achieve a single mode fiber coupling efficiency of 10{\%}. Thus, we demonstrate overall efficiency of single ion to single mode fiber fluorescence at 4{\%}. Recently, we built an updated version with an improved control of the ion position, where piezoelectric actuators applied to a movable electrode. In this setup we can fully compensate the ion micromotion while placing the ion in the focus of the mirror. We demonstrated entanglement between a single barium ion and a single emitted photon [1]. Our goal now is to entangle two ions in separate parabolic mirror traps, eventually to be separated by a kilometer or more. [Preview Abstract] |
Wednesday, June 10, 2015 8:12AM - 8:24AM |
G7.00002: Exploring a high-dimensional Hilbert space using hyperentangled photons Aditya Sharma, Kevin McCusker, Julio Barreiro, Paul Kwiat Quantum entanglement exhibits many interesting features that emerge only in high-dimensional systems. One of the most fascinating is bound entanglement, entanglement that cannot be extracted using only local operations and classical communication: a famous example is the four-qubit Smolin state. Because of its relatively high dimensionality, the Smolin state had not been experimentally observed until recently, and all previous photonic realizations relied on randomly selected unitary operations to introduce decoherence. Here we present an experiment in which we use hyperentangled photons to prepare the Smolin state. Since it does not use random unitaries, our source can be used to prepare a variety of other high-dimensional states as well. [Preview Abstract] |
Wednesday, June 10, 2015 8:24AM - 8:36AM |
G7.00003: Quantum correlations of an entangled state propagating through a phase-sensitive amplifier Tian Li, Brian Anderson, Travis Horrom, Ryan Glasser, Kevin Jones, Paul Lett We investigate the advance and delay of information transmitted through an optical phase-sensitive amplifier (PSA). We start with a two-mode entangled state created by four-wave mixing in hot $^{85}$Rb vapor and measure the mutual information shared by the two modes. We then pass one of these two modes through a PSA and investigate the shift of the mutual information as a function of the PSA phase. The cross-correlation between the two modes of a bipartite EPR state can be advanced by propagation through a fast-light medium[U. Vogl, \textit{et al.}, New J. Phys. \textbf{16}, 013011 (2014)]and, the extra noise added by a phase-insensitive amplifier has been shown to limit the advance of entanglement, preventing the mutual information from traveling superluminally[J. B. Clark, \textit{et al.}, Nat. Photon. \textbf{8}, 515 (2014)]. In the case of a PSA, however, it is well known that no extra noise will be added for the correct PSA phase (e.g. at the maximal amplification and the maximal deamplification). It is therefore of interest to examine the behavior of the dispersion and the mutual information when passing a signal through a PSA operated at different phases. The behavior of other correlation measures like the quantum discord will be presented as well. [Preview Abstract] |
Wednesday, June 10, 2015 8:36AM - 8:48AM |
G7.00004: Polarization-Frequency Entangled Narrowband Photon Pairs Chi Shu, Xianxin Guo, Peng Chen, M.M.T. Loy, Shengwang Du We demonstrate a robust scheme to produce narrowband biphotons with polarization-frequency-coupled entanglement from spontaneous four-wave mixing (SFWM) in laser cooled atoms with a right-angle geometry. Making use of an acousto-optic modulator and polarization-dependent two-photon interference, we create a coupled hyperentanglement between the polarization and frequency domains from unentangled SFWM photon pairs. We further demonstrate that, making use of the coupling effect, we can transfer the phase of a complex polarizer into the frequency entanglement and create a tunable two-mode frequency entangled Bell state. [Preview Abstract] |
Wednesday, June 10, 2015 8:48AM - 9:00AM |
G7.00005: Control of Coherence Areas in Entangled Twin Beams Matthew Holtfrerich, Alberto Marino We demonstrate the ability to control the size of the coherence area in entangled twin beams generated with four-wave mixing (FWM) in a rubidium vapor cell by controlling the size and profile of the pump beam required for the FWM. The coherence area corresponds to the smallest spatial subareas in the twin beams that are quantum correlated. Its size is directly related to the number of spatial modes that make up the twin beams and a reduction of its size leads to an increase in the number of modes. We measure the noise properties of different spatial regions of the twin beams to determine the size of the coherence area. Furthermore, we have developed a model based on fundamental physics with which to compare our data and extract the size of the coherence area. Our results show a factor of 2 reduction in the size of the coherence area when the pump's diameter is increased from 1.5~mm to 3.2~mm. We show an additional factor of 2 reduction in the size by changing the spatial profile of the pump from a Gaussian to a flattop. The ability to control the number and size of these quantum correlated subareas has applications in quantum imaging and quantum information by adding the control of the spatial degree of freedom to the physicist's toolbox. [Preview Abstract] |
Wednesday, June 10, 2015 9:00AM - 9:12AM |
G7.00006: High teleportation rates using Rydberg-based quantum repeaters Neal Solmeyer, Qudsia Quraishi Quantum networking over long distances may be achieved using repeater protocols to generate entanglement between memory nodes [Duan\textit{ et al.,} Nature \textbf{414, }413 \quad (2001)]. Typically, long-lived memories have low entanglement generation rates. Neutral atom memories can be long-lived, emit at visible wavelengths and can be collectively excited leading to directionally emitted entangled photons. Here, we propose a simplified Rydberg-based quantum repeater based on recent work [Zhao \textit{et al.,}PRA \textbf{81}$, $052329 \quad (2010)], where we reduce the number of ground states used for entanglement generation and use only one ensemble at each node, reducing the required resources. The collective excitation allows for deterministic memory generation that is mapped into a directionally emitted photonic qubit without the use of a high finesse optical cavity. We demonstrate a protocol between multiple memories stored within a single ensemble to implement a two-qubit gate. Additionally, we predict teleportation rates of 1 Hz without the use of a high finesse optical cavity, which could be increased to kHz if efficiencies are improved over the currently realized values. We plan to explore these protocols in ultra-cold ensemble of neutral $^{\mathrm{87}}$Rb atoms and are currently building this setup. [Preview Abstract] |
Wednesday, June 10, 2015 9:12AM - 9:24AM |
G7.00007: SuperDense Teleportation for Space Applications Trent Graham, Herbert Bernstein, Hamid Javadi, Paul Kwiat The transfer of quantum information over long distances is needed for many quantum communication protocols. Unfortunately, loss and noise make it difficult to directly transmit quantum states between two distant parties. Entanglement-enhanced state communication techniques such as quantum teleportation and remote state preparation allow two remote parties with shared entanglement to exchange quantum states using classical communication. However, these techniques require extensive resources and complicated measurements to implement deterministically. In contrast, SuperDense Teleportation (SDT) can communicate quantum states deterministically with greatly reduced resources, which makes it ideal for communicating quantum information for space applications. We are implementing a SDT lab demonstration, using polarization- and time-mode entangled photons to communicate a special set of two-qubit, single-photon states between two parties. We will then investigate the possibility of a space-to-Earth implementation. I will discuss our experimental progress and the design challenges facing a practical demonstration of satellite-to-Earth SDT as well as possible extensions for measuring relativistic effects on entangled states. [Preview Abstract] |
Wednesday, June 10, 2015 9:24AM - 9:36AM |
G7.00008: Quantum random number generation for loophole-free Bell tests Morgan Mitchell, Carlos Abellan, Waldimar Amaya We describe the generation of quantum random numbers at multi-Gbps rates, combined with real-time randomness extraction, to give very high purity random numbers based on quantum events at most tens of ns in the past. The system satisfies the stringent requirements of quantum non-locality tests that aim to close the timing loophole. We describe the generation mechanism using spontaneous-emission-driven phase diffusion in a semiconductor laser, digitization, and extraction by parity calculation using multi-GHz logic chips. We pay special attention to experimental proof of the quality of the random numbers and analysis of the randomness extraction. In contrast to widely-used models of randomness generators in the computer science literature, we argue that randomness generation by spontaneous emission can be extracted from a single source.\\[4pt] [1] Strong experimental guarantees in ultrafast quantum random number generation, M. W. Mitchell, C. Abellan, W. Amaya Phys. Rev. A 91, 012314 (2015)\\[0pt] [2] Ultra-fast quantum randomness generation by accelerated phase diffusion in a pulsed laser diode, C. Abell\'an, W. Amaya, M. Jofre, M. Curty, A. Ac\'in, J. Capmany, V. Pruneri, M. W. Mitchell Opt. Express 22, 1645-1654 (2014) [Preview Abstract] |
Wednesday, June 10, 2015 9:36AM - 9:48AM |
G7.00009: Matrix Product State Open Source Code for Entangled Quantum Systems Wei Han, Michael L. Wall, Daniel Jaschke, Lincoln D. Carr Variational algorithms based on Matrix Product States (MPSs) are a common numerical approach for simulating the statics and dynamics of one dimensional quantum many body lattice systems. Our group has developed an open source MPS package named OpenMPS. The package includes algorithms for simulating both finite and infinite lattice models with general degrees of freedom, i.e. bosons, fermions, or spins. OpenMPS treats not only short-range interacting systems but also long-range interacting systems, including out-of-equilibrium dynamics. Simulation of dynamics with long-range interactions is pertinent for many AMO systems, including ultracold polar molecules in optical lattices, Rydberg atoms, and trapped ions. [Preview Abstract] |
Wednesday, June 10, 2015 9:48AM - 10:00AM |
G7.00010: Bell inequalities from group theory Mark Hillery, Ugur Guney Bell inequalities are inequalities containing probabilities of measurement results that are obeyed by probabilities that come from a local, realistic theory but can be violated if the probabilities come from quantum mechanics. They can be also be formulated as nonlocal games in which quantum mechanical resources allow for higher winning probabilities than purely classical resources. Besides their intrinsic interest, these inequalities have proven to be useful in cryptography and entanglement testing. In an earlier study, we showed that it is possible to use group actions for cyclic groups to generate two-party Bell inequalities. This has now been extended to more than two parties and to non-Abelian groups. We will explicitly look at the nonlocal games generated by two groups of 6 elements, one Abelian and one non-Abelian, and compare their structures. [Preview Abstract] |
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