Seminars coming up

[CM ICTP - Trieste]

INFORMAL Condensed Matter SEMINAR


Wednesday, 25 March   -    4:00 p.m.


Seminar Room -  Leonardo Bldg. - first floor



S.D.  JENKINS    ( Georgia Institute of Technology, Atlanta )

"Light-matter interactions for quantum information: Long-lived  
quantum memories"





Abstract

The ability to distribute and store quantum information would provide  
the potential for revolutionary technological advances from  
completely secure communication to quantum computing.  Decoherence  
and propagation losses, however, severely limit our ability to  
implement these schemes. Quantum memories cannot be continuously read  
and refreshed as classical memories can since any measurement will  
alter the underlying state.  The only option remaining is to isolate  
a memory from any external influences.

We report recent implementations long-lived memories using collective  
excitations in atomic ensembles. Scattering of a light field from an  
ensemble results in the emission of a signal photon and an imprinted  
atomic spin wave. By understanding the primary sources of the  
coherence, magnetic field and atomic motion, we show how one can  
combat their deleterious effects.  We present an analysis of the  
dynamics of retrieval of information from our memories and show how  
it was exploited to produce memory times in excess of 6  
milliseconds.  We also demonstrate how one can use controlled  
interactions with magnetic fields to execute qubit rotations during  
storage. The variation of retrieval dynamics with storage time can  
also be used as a measure of initial populations of the atomic states



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  SEMINAR on  Disorder and strong electron correlations



Thursday, 26 March      -  11:00 a.m.



Seminar Room,  Leonardo Building - first floor





Boris SVISTUNOV   ( University of Massachusetts, Amherst )



"Superfluid turbulence at T=0"



Abstract



Superfluid turbulence (ST), also known as quantum turbulence, is a  
tangle of quantized vortex lines in a superfluid.  ST can be created  
in a number of ways:

(i) as a result of non-equilibrium kinetics of Bose-Einstein  
condensation, in which case it is a manifestation of generic Kibble- 
Zurek mechanism,

(ii) in the counter-flow of normal and superfluid components,

(iii) as a result of macroscopic motion of a superfluid, in which  
case it can mimic (at large enough length scale) classical-fluid  
turbulence.



We will make an introduction to the theory of relaxation kinetics of  
superfluid turbulence at T=0. The physics of zero-temperature limit  
is very rich and attractive in view of essentially conservative  
character of vortex dynamics. The theory will allow us to interpret  
recent intriguing experiments by A. Golov and collaborators.