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DTSTAMP:20260818T065542Z
LAST-MODIFIED:20180507T190418Z
DTSTART:20180511T160000Z
DTEND:20180511T170000Z
UID:event1948@bu.edu
URL:http://physics.bu.edu/internal/events/show/1948
SUMMARY:"Fate of Orthogonality Catastrophe in driven-open quantum systems"
DESCRIPTION:Featuring Federico Tonielli\, University of Cologne\, Germany\n
	Hosted by: Anatoli Polkovnikov\n\nPart of the Condensed Matter Theory Semin
	ar Series.\n\nOrthogonality Catastrophe is a paragon of the dramatic effect
	s provoked by the interaction of a gapless quantum many body system with an
	 impurity. Its instance in real time dynamics is a universal\, algebraic de
	cay of the fidelity between the unperturbed ground state and the ground sta
	te evolved in the presence of the impurity itself.\n\nWe consider the case 
	of a quantum system subject to a local dephasing channel\, i.e. locally int
	eracting with an external Markovian bath\, that plays the role of a new typ
	e of impurity and whose dynamics is well described by a local Lindblad quan
	tum master equation. We find in this new context\, a novel\, universal\, ti
	me-resolved scaling behavior of the fidelity\, that counteracts the exponen
	tial decay due to heating\, unlike the case of unitary dynamics.\n\nThe fir
	st model we consider is the one-dimensional quantum Ising chain in transver
	se field with spin dephasing\, where we establish this novel character for 
	the fidelity by means of a resummation of the perturbative expansion.\n\nWe
	 further investigate the phenomenon in a quantum field theory of free boson
	s subject to a stochastic impurity potential\, localized in space but rando
	m in time\, constructing a functional integral expression for the fidelity.
	 The latter is computed for linear and quadratic impurity potentials\, and 
	for impurities with short correlations in time. An intriguing crossover to 
	the familiar OC is found in the limit of infinite correlation time of the i
	mpurity\, for which a physical picture is proposed. \nFinally\, we ague how
	 to detect the phenomenon through direct measurement of an accessible obser
	vable in cold atoms experiments.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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