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DTSTAMP:20210619T112236Z
UID:60bf7b09170b2262260301@ist.ac.at
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DESCRIPTION:Speaker: AndrĂ¡s Vukics\nhosted by Johannes Fink\nAbstract: A n
onequilibrium phase transition in a damped-driven open quantum system is a
transition between two robust steady states controlled by an external par
ameter. In second-order transitions the change is abrupt at a critical poi
nt\, whereas in first-order transitions the two phases can coexist in a cr
itical hysteresis domain. Here\, I present a first-order dissipative quant
um phase transition\, whose microscopic basis is that the photon blockade
in a driven Jaynes-Cummings system (single atom coupled to a single mode o
f a resonator) is broken with increasing drive power [1\,2]. The observed
experimental signature is a bimodal phase-space distribution with varying
weights controlled by the drive strength. Alternatively\, in the time doma
in\, a bistable signal is obtained\, with switching times separated by ord
ers of magnitudes from any microscopic timescales of the system\, and reac
hing up to seconds [3]. We identify a well-defined thermodynamic limit\, w
here the bistability solution develops into the first-order phase transiti
on. The bistability can be regarded as a finite-size signature of the phas
e transition\, and we can calculate the finite-size scaling exponent numer
ically [4]. Importantly\, even in the thermodynamic limit\, the stability
of phases originates from the discrete spectrum of the small quantum syste
m\, the switching being induced by the continuous weak measurement of the
system by the environment. At the end of the talk\, I will sketch the simu
lation tool used for these studies\, that is C++QED: a framework for simul
ating open quantum dynamics [5\,6] conceived for supercomputing environmen
ts.References: [1] A. Dombi et al. Eur. Phys. J. D 69\, 60 (2015) [2] H. J
. Carmichael\, Phys. Rev. X 5\, 031028 (2015) [3] J. M. Fink et al. Phys.
Rev. X 7\, 011012 (2017) [4] A. Vukics et al. Quantum 3\, 150 (2019) [5] A
. Vukics\, Comp. Phys. Comm. 183\, 1381-1396 (2012) [6] https://github.com
/vukics/cppqed
LOCATION:Heinzel Seminar Room (max. 8 people!!!) & ONLINE via Zoom\, IST Au
stria
ORGANIZER:swiddman@ist.ac.at
SUMMARY:The breakdown of photon blockade: a first-order dissipative quantum
phase transition
URL:https://talks-calendar.app.ist.ac.at/events/3218
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