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On Superradiant Phase Transitions and Effective Models in Circuit QED
Oliver Viehman
20.10.2010 at 16:00
Abstract:
Circuit QED systems of artificial atoms interacting with microwaves have been proved to behave in many respects analogously to their counterparts with real atoms in cavity QED. However, it has been predicted recently that the analogy fails if a large number of (artificial) atoms couple strongly to the elec- tromagetic radiation [1]: Whereas for real atoms a no-go theorem rules out the possibility of a superradiant quantum phase transition as the coupling is increased [2], the standard description of circuit QED systems by an effective model based on macroscopic quantities [1,3] does allow it.
We investigate the possibility of a superradiant quantum phase transition in circuit QED systems from a microscopic point of view. Our analysis shows that also circuit QED systems are subject to the no-go theorem. It hence restores the analogy of circuit QED and cavity QED and challenges the applicability of the standard description of circuit QED systems in the regime under concern. In the light of this analysis, the no-go theorem is scrutinized and confirmed in a way more adequate for realistic physical systems.
[1] P. Nataf and C. Ciuti, 1:72, doi: 10.1038/ncomms1069 (2010).
[2] K. Rzążewski, K. Wódkiewicz, and W. Żakowicz, Phys. Rev. Lett. 35, 432 (1975).
[3] A. Blais, R.-S. Huang, A. Wallraff, S. Girvin, and R. Schoelkopf, Phys. Rev. A 69, 062320 (2004).
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