Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session W33: Quantum Entanglement |
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Sponsoring Units: GQI Chair: Daniel Lidar, University of Southern California Room: Colorado Convention Center 403 |
Thursday, March 8, 2007 2:30PM - 2:42PM |
W33.00001: Entanglement Purification of Any Stabilizer State Scott Glancy, Emanuel Knill, Hilma Vasconcelos We present a method for multipartite entanglement purification of any stabilizer state shared by several parties. In our protocol each party measures the stabilizer operators of a quantum error-correcting code on his or her qubits. The parties exchange their measurement results, detect or correct errors, and decode the desired purified state. We give sufficient conditions on the stabilizer codes that may be used in this procedure and find that Steane's seven-qubit code is the smallest error-correcting code sufficient to purify any stabilizer state. An error-detecting code that encodes two qubits in six can also be used to purify any stabilizer state. We further specify which classes of stabilizer codes can purify which classes of stabilizer states. [Preview Abstract] |
Thursday, March 8, 2007 2:42PM - 2:54PM |
W33.00002: An observable entanglement measure Florian Mintert We describe how the concurrence of arbitrary mixed bipartite quantum states, can be measured in terms of a simple projective measurement on two identically prepared quantum states, and we discuss generalizations to multipartite systems. [Preview Abstract] |
Thursday, March 8, 2007 2:54PM - 3:06PM |
W33.00003: The su(1,1) symmetry of tripartite entangled Gaussian states Barry Sanders, Zahra Shaterzadeh Yazdi, Peter Turner Two-mode squeezed light has been central to theoretical and experimental studies of continuous variable quantum information processing and to quantum foundations. More recently the generalization of these states to three-mode squeezed light has been achieved in the context of quantum teleportation [1] and state sharing [2]. Theories are typically developed in Gaussian or position representations, but we have discovered that all tripartite entangled Gaussians states of these types are in fact su(1,1) coherent states with respect to an intriguing three-boson realization of su(1,1) first noticed by Sebawe Abdalla et al [3]. This symmetry provides insights into the useful properties of these states and suggests ways to generalize theories and applications of multipartite entangled Gaussian states. [1] A. Furusawa et al, Science \textbf{282}, 706 (1998). [2] A. M. Lance et al, Phys. Rev. Lett. \textbf{92}, 177903 (2004). [3] M. Sebawe Abdalla et al, Eur. Phys. J. D \textbf{13}, 423 (2001). [Preview Abstract] |
Thursday, March 8, 2007 3:06PM - 3:18PM |
W33.00004: Quantum Chaos and Entanglement for Two Coupled Spins Collin Trail, Ivan Deutsch, Leigh Norris, Parin Sripakdeevong, Arjendu Pattanayak We explore the relationship between classical chaos and the generation of quantum entanglement in a system of two coupled and driven ``tops'' e.g. electron angular momentum and nuclear spins coupled by the hyperfine interaction and driven by an applied time varying magnetic field. Chaos arises here through the coupling and time dependent drive, rather than the coupling of independently chaotic subsystems, as has been previously studied. Using the same Hamiltonian to generate both classical and quantum dynamics, we find that the long time averages of the entanglement generated between two initially uncoupled coherent spin states correlates with the structure of the mixed classical phase space and interpret these results. [Preview Abstract] |
Thursday, March 8, 2007 3:18PM - 3:30PM |
W33.00005: Entanglement Entropy in Gapped Quantum Spin Chains Hosho Katsura, Takaaki Hirano, Yasuhiro Hatsugai Entanglement properties of quantum spin systems have recently attracted much attention in quantum information theory and condensed matter physics. The entanglement entropy (von Neumann entropy of a sub-system) has been used to detect the quantum phase transition and topological order[1][2][3]. It was also discussed that the direct relation between the bulk entanglement entropy and the edge one [4]. We give the exact form of the entanglement entropy in higher-spin Valence-Bond- Solid states and show that the edge state picture is valid for all integer spins. The relationship between the entanglement entropy and the correlation function is clarified and the physical meaning of the entanglement entropy in gapped models is established. We also make a comparison between the analytical results for VBS chains and the numerical results for higher-spin antiferromagnetic Heisenberg chains. [1] M. Levin and X. G. Wen, Phys. Rev. Lett. {\bf 96}, 110405 (2006). [2] A. Kitaev and J. Preskill, Phys. Rev. Lett. {\bf 96}, 110404 (2006). [3] G. Vidal et al., Phys. Rev. Lett. {\bf 90}, 227902 (2003). [4] S. Ryu and Y. Hatsugai, Phys. Rev. Lett {\bf 96}, 245115 (2006). [Preview Abstract] |
Thursday, March 8, 2007 3:30PM - 3:42PM |
W33.00006: ABSTRACT WITHDRAWN |
Thursday, March 8, 2007 3:42PM - 3:54PM |
W33.00007: ABSTRACT WITHDRAWN |
Thursday, March 8, 2007 3:54PM - 4:06PM |
W33.00008: Experimental purification of two-atom entanglement in an ion trap array D. Leibfried, R. Reichle, E. Knill, J. Britton, R. B. Blakestad, J. D. Jost, C. Langer, R. Ozeri, S. Seidelin, D. J. Wineland Entanglement is a crucial resource for quantum information processing and quantum communication. Distributed entanglement is created by preparing an entangled pair of quantum particles in one location and transporting one member of the pair to another location. Decoherence during transport reduces the fidelity of the entanglement. ``Entanglement purification'' [ C. Bennett \textit{et al.}, Phys. Rev. Lett. \textbf{76}, 722 (1996)] can improve the fidelity after the transport using local quantum operations and classical communication between locations to distill high fidelity entangled pairs from lower fidelity ones. Proof-of-principle experiments distilling entangled photon pairs have previously been carried out, however, distilled pairs were obtained with low probability of success and required destruction of the entangled pairs, making them unavailable for further processing. We have implemented efficient and non-destructive entanglement purification with atomic (ion) quantum bits in a multi-zone trap. Two noisy entangled pairs were created and distilled into one higher fidelity pair available for further use. Success probabilities were above 35 {\%}. [Preview Abstract] |
Thursday, March 8, 2007 4:06PM - 4:18PM |
W33.00009: Entanglement Dynamics of Two-Atom Jaynes-Cummings Model under Phase Telegraph Noise Huseyin Karacali, Resul Eryigit We have analyzed the entanglement dynamics in a two atom one-field mode Jaynes-Cummings model with stochastic atom-field interactions. The phase of the interaction term is subject to a two level telegraph noise which is characterized by a dwell time and jump magnitude. We have investigated the effect of noise characteristics on the entanglement between the field and the atom as well as atom1 and atom2. The field-atom entanglement is found to be damped to zero because of the noise, as expected. However,the noise is found to be cooperative for the atom entanglement, as it approaches 0.25 in the long time limit independent of the characteristics of the noise. [Preview Abstract] |
Thursday, March 8, 2007 4:18PM - 4:30PM |
W33.00010: Nonequilibrium thermal entanglement Luis Quiroga, Ferney Rodriguez, Maria Ramirez, Roberto Paris For quantum systems in contact with heat reservoirs at an unique and fixed temperature the equilibrium thermal entanglement has been extensively studied. However, the entanglement of nonequilibrium quantum systems has been scarcely considered. New possibilities for entanglement production and manipulation in nonequilibrium situations, where quantum coherences are dominant, are emerging. The aim of the present work is to correlate thermodynamical nonequilibrium steady-state features with entanglement properties of quantum nanosystems. We show an intimate relationship between stationary heat current, entropy production rate and entanglement for a simple quantum system coupled to two heat baths at different temperatures. We show that while the quantum informational entropy remains constant in a steady-state situation, the rate of production of thermodynamic entropy is linearly proportional to the nonequilibrium concurrence. We find an enhanced-suppressed entanglement transition which takes place when a temperature gradient is applied. Additionally, a temperature gradient allows for producing quantum states with exactly the same amount of entanglement as for an equilibrium situation but with different entropies and heat currents. [Preview Abstract] |
Thursday, March 8, 2007 4:30PM - 4:42PM |
W33.00011: Thermal entanglement in two double quantum dots Lesvia-Debora Contreras-Pulido, Fernando Rojas Entanglement has become an important resource in quantum information processing, it is important to quantify the degree of entanglement between two qubits at a finite temperature [1]. As charge qubits realized in double quantum dots are promising solid state candidates for both qubit and entangled states realization, we explore theoretically the non-zero entanglement generation between two charge qubits surrounded by a thermal environment and under the effect of an external asymmetric electric field. The qubits array is described by a Hubbard-type Hamiltonian which is diagonalized in order to calculate the equilibrium thermal density matrix, used to quantify the entanglement by Wootters' concurrence. We find that the qubits exhibit thermal entanglement that vanishes at finite temperature and we show that concurrence depends on both tunneling and the external potential. The critical value for which concurrence vanishes presents a parabolic dependence with the external potential, which is a controllable parameter in quantum dots through gate voltages. We acknowledge support from projects DGAPA-IN114403 and CONACyT -43673-F. [1]. Arnesen et al., Phys.Rev.Lett 87,017901 (2001) [2]. Wootters Phys. Rev. Lett. 80, 2245 (1998) [Preview Abstract] |
Thursday, March 8, 2007 4:42PM - 4:54PM |
W33.00012: Comparisons of experimental entanglement witnesses and measures for a two-qubit system K.A. Walsh, A.J. Schauf, J.S. Lesniak, E.C. Behrman, J.E. Steck, S.R. Skinner A single operator cannot measure the entanglement for a general state; however, knowledge of the density matrix enables computation of any universal entanglement measure. Several entanglement witnesses have been proposed for two-qubit systems. We compare these to published measures. [Preview Abstract] |
Thursday, March 8, 2007 4:54PM - 5:06PM |
W33.00013: A non-Markovian optical signature for detecting entanglement in coupled excitonic qubits Ferney Rodriguez, Luis Quiroga, Neil Johnson We identify an optical signature for detecting entanglement in experimental nanostructure systems comprising coupled excitonic qubits. This signature owes its strength to {\em non-Markovian} dynamical effects in the second-order temporal coherence function of the emitted radiation. We calculate autocorrelation and cross-correlation functions for both selective and collective light excitation, and prove that the coherence properties of the emitted light do indeed carry information about the entanglement of the initial multi-qubit state.We also show that this signature can survive in the presence of a noisy environment. [Preview Abstract] |
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