Publications (4)4.98 Total impact
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ABSTRACT: We investigate a fundamental limitation on, the measurement of spatial coherence for highly incoherent fields. We model the nearfield detection scheme, required for such a measurement, with pointlike induced dipoles. We find that this fully vector model sets a characteristic length scale beyond which the spatial eoherence of an optical field cannot be accurately measured. This length scale forms an uncertainty relationship with the photodetector integration time. (C) 2003 Optical Society of America.  [Show abstract] [Hide abstract]
ABSTRACT: Using a scalar dipole model, we find that the fundamental limitation on the measurement of spatial coherence by nearfield probes can be understood in terms of a simple scattering model.  [Show abstract] [Hide abstract]
ABSTRACT: Characterizing entanglement in all but the simplest case of a two qubit pure state is a hard problem, even understanding the relevant experimental quantities that are related to entanglement is difficult. It may not be necessary, however, to quantify the entanglement of a state in order to quantify the quantum information processing significance of a state. It is known that the fully entangled fraction has a direct relationship to the fidelity of teleportation maximized under the actions of local unitary operations. In the case of two qubits we point out that the fully entangled fraction can also be related to the fidelities, maximized under the actions of local unitary operations, of other important quantum information tasks such as dense coding, entanglement swapping and quantum cryptography in such a way as to provide an inclusive measure of these entanglement applications. For two qubit systems the fully entangled fraction has a simple known closedform expression and we establish lower and upper bounds of this quantity with the concurrence. This approach is readily extendable to more complicated systems.  [Show abstract] [Hide abstract]
ABSTRACT: Summary form only given. Characterizing the entanglement of a general bipartite quantum system is a difficult problem. Most measures involve difficult extremizations and their physical motivation is not always clear. In this paper we propose an experimental measure of entanglement based on a modified version of the familiar teleportation protocol of Bennett et al. (1993). Briefly, teleportation traditionally involves two parties, Alice and Bob. Initially, Alice has a qubit in an unknown quantum state which she would like to communicate to Bob and Bob has two qubits in an entangled EinsteinPodolskyRosen (EPR) pair. To accomplish this transfer, Bob shares one qubit of his EPR pair with Alice. She then performs a joint measurement or Bell measurement on her two qubits and relays this information back to Bob over a classical channel. Bob then uses the outcome of Alice's Bell measurement to transform his qubit, with a local unitary transformation, into the original quantum state, always with a fidelity of one.
Publication Stats
30  Citations  
4.98  Total Impact Points  
Top Journals
 Optics Letters (1)
 Physics Letters A (1)
Institutions

2002

Los Alamos National Laboratory
Los Alamos, California, United States
