[Aspuru-Guzik Group List] ITAMP Lunch Seminar (Nov. 9th) - John Sous, University of British Columbia
7 Nov
2017
7 Nov
'17
11:07 p.m.
Speaker: John Sous, (University of British Columbia)
Date: Thursday, November 9th
Time: 12:00-1:00 pm
Includes Pizza.
Title: Phonon-mediated repulsion, sharp transitions and (quasi)self-trapping in the
extended Peierls-Hubbard model
Abstract: Particle-phonon coupling is generically expected to lead to a screening of the
bare particle-particle interactions. If low-energy overscreening occurs, the resulting
attractive interactions are responsible for conventional superconductivity as described by
the Bardeen-Cooper-Schrieffer theory. I will demonstrate that Peierls-type
particle-phonon coupling not only leads to an enhanced repulsion between identical
fermions/hard-core bosons, but also generates an additional effective interaction not of
density-density type and thus not involved in screening. This interaction moves pairs of
neighbor particles as a whole; this has unusual consequences such as a
(quasi)self-trapping transition for a bound pair even when the individual particles are
very mobile. These results open new directions in the study and understanding of the
effects of particle-boson coupling, relevant for understanding behavior in Physics, e.g.
in quantum materials; Chemistry, e.g. in optoelectronic processes; and Biology, e.g. in
photosynthesis and DNA.
Location: B-106 @ Center for Astrophysics (60 Garden Street)
Directions: After entering the lobby of the CfA, turn right to enter the hallway of the B
building. In the hallway, turn right again, B-106 will be at the end of the hallway on the
left side.
30 Apr
30 Apr
10:58 a.m.
New subject: [Aspuru-Guzik Group List] ITAMP Lunch Seminar (May. 3rd) - Francesco Ciccarello (University of Palermo)
Speaker: Francesco Ciccarello (University of Palermo)
Date: Thursday, May 3rd
Time: 12:00-1:00 pm
Includes Pizza.
Title: Quantum collision models
Abstract: A collision model (or repeated-interactions model or conveyor-belt model) is a
simple theoretical framework in which a system S undergoes successive interactions
(“collisions”) with the subunits of a large environment [1-4]. Currently, quantum
collision models are being used more and more in research areas such as open quantum
systems theory (especially non-Markovian dynamics [5]), quantum thermodynamics [6],
quantum optics [7] and, in some respects, even quantum gravity [8].
Here, starting from a few historical notes, we will present a general introduction to
quantum collision models. In particular, we will discuss: their tight connection with the
concept of CP-divisibility (CP standing for “completely positive”) and weak quantum
measurements; the issue of their continuous-time limit; the possibility to derive the
Lindblad master equation with no approximations; the different ways to modify their basic
definition so as to introduce memory effects; the possibility of deriving well-defined
non-Markovian master equations; their relationship with the input-output formalism of
quantum optics.
[1] J. Rau, Phys. Rev. 129, 1880 (1963).
[2] C. M. Caves and J. G. Milburn, Phys. Rev. A 36, 5543 (1987).
[3] T. A. Brun, Am. J. Phys. 70, 719 (2002).
[4] V. Scarani M. Ziman, P. Stelmachovic, N. Gisin, and V. Buzek, Phys. Rev. Lett. 88,
097905 (2002).
[5] F. Ciccarello, G. M. Palma, and V. Giovannetti, Phys. Rev. A 87, 040103(R) (2013).
[6] P. Strasberg, G. Schaller, T. Brandes, and M. Esposito, Phys. Rev. X 7, 021003
(2017).
[7] A. Grimsmo, Phys. Rev. Lett. 115, 060402 (2015); H. Pichler and P. Zoller, Phys. Rev.
Lett 116,093601(2016); F. Ciccarello, Quantum Meas. Quantum Metrol. 4,53 (2017); J. A.
Gross, C. M. Caves, G. J. Milburn, and J. Combes, Quantum Sci. Technol. 3, 024005 (2018).
[8] N. Altamirano, P. Corona-Ugalde, R. Mann, and M. A. Zych, New J. Phys. 19, 013035
(2017).
Directions: After entering the lobby of the CfA (60 Garden street), turn right to enter
the hallway of the B building. In the hallway, turn right again, B-106 will be at the end
of the hallway on the left side.
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participants (1)
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Hannes Pichler