Bulletin of the American Physical Society
2006 37th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 16–20, 2006; Knoxville, TN
Session L4: Entanglement |
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Chair: Barry Sanders, University of Calgary Room: Knoxville Convention Center 301E |
Thursday, May 18, 2006 10:30AM - 10:42AM |
L4.00001: Heralded entanglement between remote atomic ensembles Hugues de Riedmatten, Chin-Wen Chou, Daniel Felinto, Sergey Polyakov, Jeff Kimble, Steven van Enk A critical requirement for diverse applications in Quantum Information Science is the capability to disseminate quantum resources over complex quantum networks. This requires deterministic or heralded storage of entanglement between remote locations. Atomic ensembles appear to be a promising candidate for this task . In this contribution we report observations of entanglement between two atomic ensembles located on different tables in distinct apparatuses separated by 2.8 meters [1]. Quantum interference in the detection of a photon emitted by one of the samples projects the otherwise independent ensembles into an entangled state with one joint excitation stored remotely in $\sim $10$^{5}$ atoms at each site. After a delay of 1 $\mu $s to demonstrate quantum memory, we confirm entanglement by mapping the state of the atoms to optical fields and by measuring mutual coherences and photon statistics for these fields. We thereby determine a quantitative lower bound for the entanglement of the joint state of the ensembles. Although the entanglement creation is probabilistic, the initial detection heralds unambiguously the creation of an entangled state between the two ensembles, which can be stored and is physically available for subsequent utilization. [1] C.W. Chou et al, Nature \textbf{438,} 828-832(2005) [Preview Abstract] |
Thursday, May 18, 2006 10:42AM - 10:54AM |
L4.00002: Quantum Chaos and Entanglement for Two Coupled Spins Collin Trail, Ivan Deutsch, Arjendu Pattanayak, Parin Sripakdeevong Recent work suggests that there is a connection between the rate of entanglement generation of a bipartite quantum mechanical system and the existence of chaos in the classical limit of that system. This work further explores this connection for the case of two spins in an atom, electron and nuclear, coupled by the hyperfine interaction and driven by a time varying external magnetic field. In contrast to other work, we are considering a system which is chaotic only when coupling exists between the subsystems, rather than one made of two independently chaotic subsystems. We have studied numerical simulations of the classical limit of this system and explore the parameter space that shows the appearance or lack of chaos for a variety of different fields and initial conditions. For a quantum mechanical wave packet placed in the regular and chaotic regions of a mixed space, we compare the rate of entanglement generation. [Preview Abstract] |
Thursday, May 18, 2006 10:54AM - 11:06AM |
L4.00003: Observable entanglement measures Florian Mintert, Stephen Walburn, Paulo Souto Ribeiro, Luiz Davidovich, Andreas Buchleitner We discuss the entanglement measure {\it concurrence} as an experimentally accessible quantity. In contrast to the original definition, the present is based only on physical observables. Therefore, concurrence can experimentally be measured without state reconstruction via quantum state tomography. The non-linearity necessary for any entanglement measure can be provided by measurements on two copies of the system states. [Preview Abstract] |
Thursday, May 18, 2006 11:06AM - 11:18AM |
L4.00004: Towards Feedback Control of Entanglement Jin Wang, Stefano Mancini A model to investigate feedback control of entanglement is provided. It consists of two two-level atoms placed in two distant cavities interacting through a radiation field in a dispersive way. The spin-spin interaction of these two atoms can be described by an Ising model. The steady-state entanglement is improved in the two atom system by using feedback. [Preview Abstract] |
Thursday, May 18, 2006 11:18AM - 11:30AM |
L4.00005: Experimental Atom-Photon Entanglement: Markus Weber, Juergen Volz, Wenjamin Rosenfeld, Stefan Berner, Florian Henkel, Christian Kurtsiefer, Harald Weinfurter Entanglement between light and matter is a key resource for new applications in quantum communication and information forming the interface between atomic quantum memories and photonic quantum communication channels [1,2]. Especially for applications like quantum networks or the quantum repeater, atom-photon entanglement enables one to generate entanglement between atoms at remote locations [2,3]. Here we report the observation of high-fidelity entanglement between a single optically trapped $^{87}$Rb atom and a single spontaneously emitted photon at a wavelength of 780 nm. To verify the entanglement we introduce a single atom state analysis. This technique is used for full state tomography of the atom-photon qubit-pair. The efficiency of the atomic state detection and the observed entanglement fidelity are high enough to allow in a next step the generation of entangled atoms at large distances, ready for a final loophole-free test of Bell's inequality. [1] B. Blinov et al., Nature {\bf 428}, 153 (2004). [2] J. Volz \& M. Weber et al., Phys. Rev. Lett. {\bf 96}, (2006). [3] C. Simon et al., Phys. Rev. Lett. {\bf 91}, 110405 (2003). [Preview Abstract] |
Thursday, May 18, 2006 11:30AM - 11:42AM |
L4.00006: Remote phase shifting of an interferometer using entangled-state correlations. Enrique Galvez, Mehul Malik, Brad Melius We describe an experiment involving polarization-entangled photon pairs where one photon of a pair is sent to a Mach-Zehnder interferometer and the other one to a geometric-phase shifter. The interferometer is configured to interfere two Bell states via the arms of the interferometer [1]. The phase shifter introduces a Pancharatnam-Berry phase between the product states that make up the entangled states. Polarizers placed after the interferometer project the state of the pairs such that the remote phase adds to the dynamical phase of the interferometer. Thus, the phase and amplitude of the interference pattern is determined by actions on the path of the photons not going through the interferometer. Experimental results confirm the theoretical predictions. [1] M.J. Pysher et al. Phys. Rev. A 72, 052327 (2005). [Preview Abstract] |
Thursday, May 18, 2006 11:42AM - 11:54AM |
L4.00007: Distribution of entanglement in an ion trap array J.D. Jost, C. Langer, R. Ozeri, R.B. Blakestad, J. Britton, J. Chiaverini, D.B. Hume, W.M. Itano, E. Knill, D. Leibfried, R. Reichle, T. Rosenband, S. Seidelin, J.H. Wesenberg, D.J. Wineland Atomic ions confined in radio frequency traps provide a scalable system for quantum information processing. To implement complex quantum algorithms, sympathetic cooling, long coherence times, multiple trapping zones, and high fidelity coherent operation are necessary. These requirements have been demonstrated in separate experiments. Current experimental work at NIST involves combining these elements. This report describes progress towards the use of $^{24}$Mg$^{+}$ to sympathetically cool $^{9}$Be$^{+}$ qubits, which will mitigate motional heating and enable multiple high fidelity entangling operations in different trapping zones. Combined with laser beams that address multiple trap zones, this should allow the realization of distributed entanglement and advanced quantum algorithms. [Preview Abstract] |
Thursday, May 18, 2006 11:54AM - 12:06PM |
L4.00008: Entanglement of remote atomic qubits Dzmitry Matsukevich, Thierry Chaneliere, Stewart Jenkins, Shau-Yu Lan, Brian Kennedy, Alex Kuzmich We report observations of entanglement of two remote atomic qubits, achieved by generating an entangled state of an atomic qubit and a single photon at Site A, transmitting the photon to Site B in an adjacent laboratory through an optical fiber, and converting the photon into an atomic qubit. Entanglement of the two remote atomic qubits, each qubit consisting of two independent spin wave excitations, is inferred by performing, locally, quantum state transfer of each of the atomic qubits onto a photonic qubit and subsequent measurement of polarization correlations in violation of the Bell inequality $|S| <2$. We experimentally determine $S = 2.16 \pm 0.03.$ [Preview Abstract] |
Thursday, May 18, 2006 12:06PM - 12:18PM |
L4.00009: Spooky Phenomena in Two-Photon Processes Ming-Chiang Li A spooky phenomenon in two-photon coherent atomic absorption was discussed in 1980 [M. C. Li, \textit{Phys. Rev. A }\textbf{22 }(1980) 1323]. The absorption was initiated by two different laser sources. Classically, it is impossible for atoms to transit coherently in the absorption process, but quantum mechanically it is. This is one of the spooky phenomena in quantum mechanic. Around1990, there were very active experimental pursuits on a spooky phenomenon of two photons emitted from crystal parametric down conversion. The two-photon coherent atomic absorption process contained all basic ingredients as that in crystal parametric down conversion. However, the former arises from two different laser sources. The atom entangles two photons together and becomes a correlatior. The latter arises from a single laser source and two photons are entangled with each other at emission. These two spooky phenomena have been considered as disjointed. The present talk will review two spooky phenomena, and point out their similarities. The investigation on quantum spooky phenomena has led to quantum computing and quantum encryption. It is a hope that the present will stimulate the interest on bring in these two disjointed phenomena together and provide clues in advancing quantum computing and quantum encryption. [Preview Abstract] |
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