Southwest Quantum Information and Technology

Tenth Annual Meeting, February 14-17, 2008
University of New Mexico, Santa Fe, New Mexico

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SESSION 15: Breakout III - Quantum Information B
Session Chair:
12:00-12:30	Haitao Quan, Los Alamos National Laboratory
	quantum thermodynamic cycles and quantum heat engines
	Abstract. In this work, We are trying to make quantum mechanical generation of thermodynamics. our discussion will focus on the so-called quantum heat engines, which use quantum mechanical systems as the working substance. Quantum heat engines have some different properties from their classical counterpart. In order to describe quantum heat engines, we systematically studyisothermal and isochoric processes for quantum thermodynamic cycles. Based on these results the quantum versions of both the Carnot heat engine and the Otto heat engine are defined without ambiguities. We also study the properties of quantum Carnot and Otto heat engines in comparison with their classical counterparts. In addition, we discuss the role of Maxwell\'s demon in quantum thermodynamic cycles. We find that there is no violation of the second law, even in the existence of such a demon, when the demon is included correctly as part of the working substance of the heat engine.
12:30-13:00	Gilad Gour, Institute of Quantum Information Science
	Polygamy of entanglement of assistance: duality for monogamy of entanglement
	Abstract. In contrast to classical multi-partite systems, which can enjoy arbitrary correlations between components, shared entanglement is restricted in a multipartite system. In this talk I will introduce a duality for monogamy of entanglement: whereas monogamy of entanglement inequalities provide an upper bound for bipartite sharability of entanglement in a multipartite system, I will show that the same quantity provides a lower bound for distribution of bipartite entanglement in a multipartite system. I will then show that our results for monogamy of entanglement can be used to establish relations between bipartite entanglement that separate one qubit from the rest vs separating two qubits from the rest.
13:00-13:30	Paul M. Alsing, University of New Mexico
	Spin-induced non-geodesic motion, Wigner rotation and EPR correlations of massive spin-1/2 particles in a gravitational field
	Abstract. We investigate in a covariant manner, the spin-induced non-geodesic motion of massive spin-1/2 particles in an arbitrary gravitational field for trajectories that are initially geodesic when spin is ignored. Using the WKB approximation for the wave function in an arbitrary curved spacetime, we compute the O(hbar) correction to the Wigner rotation of the spin-1/2 particle, whose O(1) contribution is zero on timelike geodesics. We consider specific examples in the Schwarzschild metric for motions in the equatorial plane for (i) particles falling in from spatial infinity with non-zero angular momentum and (ii) circular geodesic orbits. For the latter case we consider the Bell inequalities for a perfectly anti-correlated EPR entangled pair of spins as the separate qubits traverse the circular geodesic in opposite directions.
13:30-14:00	Animesh Datta, University of New Mexico
	Entanglement is an important resource ??!!
	Abstract. We attempt at characterizing the correlations present in the quantum computational model DQC1, introduced by Knill and Laflamme [Phys. Rev. Lett. 81, 5672 (1998)]. The model involves a collection of qubits in the completely mixed state coupled to a single control qubit that has nonzero purity. Although there is little or no entanglement between two parts of this system, it provides an exponential speedup in certain problems. On the contrary, we find that the quantum discord across the most natural split is nonzero for typical instances of the DQC1 ciruit. Nonzero values of discord indicate the presence of nonclassical correlations. We propose quantum discord as figure of merit for characterizing the resources present in this computational model. This might be a complementary measure for counting resources in quantum information science.