Dear all,
Here is an announcement of a seminar by Prof. Gen Kimura (Shibaura Institute of Technology).
For those who wish to attend it, send me an e-mail to
hatano@iis.u-tokyo.ac.jp <mailto:hatano@iis.u-tokyo.ac.jp>
for the zoom link.
For other seminars in the same series, see
sites.google.com/view/statphys-seminar <sites.google.com/view/statphys-seminar>
best,
Naomichi Hatano
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Speaker : Prof. Gen Kimura (Shibaura Institute of Technology)
Date : Monday, 21 June 2021, 10:00 ~ 11:00 JST
Title : Universal constraint on relaxation times for Quantum Dynamical Semigroup
Abstract :
In order to realize practical quantum devices such as quantum computer, one always has to overcome a noise, especially a decoherence, in order to keep a quantum coherence. However, the general nature of decoherence is still missing even from the theoretical point of view. Quantum dynamical semigroup describes a general Markovian dynamics of an open quantum system, incorporating the conditions of complete positivity (CP) and trace preservation (TP).
The generator of the equation has a nice representation which is nowadays called a GKLS (Gorini-Kossakowski-Lindblad-Sudarshan) generator.
A decoherence process is characterized by relaxation times, from which one knows a time scale to keep a quantum coherence.
In this talk, we discuss there is a universal constraint for relaxation times which is satisfied for any GKLS generator, i.e., for any quantum dynamical semigroup.
By introducing new matrix inequalities, which themselves are interesting from mathematical point of view, we derive several constraints tighter than the bounds known so far. We also give a conjecture for the tightest constraint.
Due to the universality and its experimental accessibility, we believe that our constraint gives a physical manifestation of the completely positive condition (in the same spirit of Bell’s theorem).
References:
* V. Gorini, A. Kossakowski, and E. C. G. Sudarshan, J. Math. Phys. 17, 821 (1976).
* G. Lindblad, Comm. Math. Phys. 48, 119 (1976).
* G. Kimura, Phys. Rev. A 66, 062113 (2002).
* G. Kimura, S. Ajisaka, K. Watanabe, Open Syst. Inform. Dynam. 24(4): 1-8 (2017).
* D. Chruscinski, G. Kimura, A. Kossakowski, Y. Shishido, arXiv:2011.10159 (2020).
* G. Kimura, R. Fujii, H. Hiromichi, D. Chruscinski (in prep.)
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Naomichi Hatano
Institute of Industrial Science, University of Tokyo
Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8574, JAPAN
Phone: +81-4-7136-6961
Fax: +81-4-7136-6978
hatano-lab.iis.u-tokyo.ac.jp/hatano/
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