**Date: Friday, August 24, 2012**

Time: 10:00am

Location: PHYS 401

__Title__

Phase Entanglement With Macroscopic Coherent States

__Abstract__

Entanglement is one of the defining features of quantum mechanics, with current applications in communications and cryptography, but with a wide range of possible future technologies such as quantum computing. Most entanglement experiments use single photons as the carriers of entanglement, and are therefore limited in distance because of the effects of absorption. Entanglement in macroscopic systems such as coherent states with large amplitudes has been suggested in terms of Schrodinger cat states, but rely on large nonlinearities making them unrealistic. In this proposal a method for performing nonlocal interferometry with entangled macroscopic coherent states created using weak nonlinearities is described. In addition an accompanying quantum key distribution scheme is outlined. An analysis of the effects of loss on such a system shows that a large number of photons can be absorbed from the coherent states with only a small loss in visibility. This result along with an entanglement swapping method may allow for greatly improved distances for quantum communications than currently possible.