[quantum-info] Thursday August 25, noon, IQC, RAC1 2009: Misha Brodsky

[Marco Piani]

Misha Brodsky
AT&T Labs


Title: "Decoherence of polarization entanglement in optical fibers "



Abstract

Quantum mechanics permits the existence of unique correlations, or  
entanglement, between individual particles. The ability of entangled  
particles to act in concert is preserved even when they are separated  
by large distances and thus serves as a resource for numerous  
applications. For example, distributing entangled photon pairs between  
remote parties potentially enables secure communication or could offer  
the possibility of interconnecting quantum computers. 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 this task. The bond between  
entangled photons is, however, very fragile and could be lost.

  Several physical phenomena set limitations on transmission of  
classical light pulses through optical fibers. An intriguing and  
crucial question is how some of these well-studied phenomena, for  
instance Polarization Mode Dispersion (PMD), arising from inherent  
defects and miniscule imperfections in fibers, affect a polarization  
entangled photon pair. How far could one send entangled photons while  
still maintaining the connection between them?

We investigate, theoretically and experimentally, PMD-induced  
degradation of entanglement between two photons transmitted over  
fibers. We show that the loss of entanglement could be either gradual  
or surprisingly abrupt. In addition, we point to cases in which the  
adverse effect of fiber propagation could be self compensated.  
Finally, we define the range of fiber parameters over which  
entanglement remains sufficient for secure communication. The richness  
of the observed phenomena suggests that fiber-based entanglement  
distribution systems could serve as natural laboratories for studying  
entanglement decoherence.

Biography
Dr. Misha Brodsky joined AT&T Labs in 2000. His contributions to fiber  
optic communications focused on optical transmission systems and  
physics of fiber propagation, most notably through his work on  
polarization effects in fiber-optic networks. More recently Misha has  
been working on quantum communications; single photon detection; where  
his prime research interest is in photon entanglement and entanglement  
decoherence mechanisms in optical fibers.

Dr. Brodsky has authored or co-authored over 70 journal and conference  
papers, a book chapter and about two dozen patent applications. He is  
a topical editor for Optics Letters and has been active on numerous  
program committees for IEEE Photonics Society and OSA conferences. Dr.  
Brodsky holds a PhD in Physics from MIT.


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