Colloquium: Dr. Michael Brodsky, Army Research Lab

Location

Physics : 401

Date & Time

November 18, 2015, 3:30 pm4:30 pm

Description

TITLE: "Decoherence of polarization entanglement in optical fibers "

ABSTRACT: Quantum mechanics permits the existence of unique correlations, or entanglement, between individual particles. For a pair of entangled photons, this means that performing a measurement on one photon appears to affect the state of the other. In the other words entangled particles act in concert even when they are separated by large distances. This ability serve as a resource for potential beyond-classical capabilities for Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) for stationary and mobile Army elements. For example, spatially distributed entanglement could enable secure tamper-evident long-haul communications, a network of high-precision clocks, sensors operating in quantum regime. The vast transparency band of the installed global fiber-optic network, consisting of over a Gigameter of optical fiber cables, presents a particularly attractive opportunity for entanglement distribution. The bond between entangled photons is, however, very fragile and could be lost. How far could one send entangled photons while still maintaining the connection between them? We investigate, theoretically and experimentally, how inherent defects and miniscule imperfections in fiber-optic cables degrade entanglement between two photons transmitted over fibers. We show that the loss of entanglement could be either gradual or surprisingly abrupt. We describe relation between local and non-local effects and suggest a novel non-local way to compensate for adverse effects that occur during propagation in fibers. Finally, we will touch upon the scaling of the point-to-point entanglement degradation in networks. The richness of the observed phenomena suggests that fiber-based entanglement distribution systems could serve as natural laboratories for studying entanglement decoherence.