English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In cavity quantum electrodynamics (QED), the interaction between an atomictransition and the cavity field is measured by the vacuum Rabi frequency$\Omega_0$. The analogous term "circuit QED" has been introduced for Josephsonjunctions, because superconducting circuits behave as artificial atoms coupledto the bosonic field of a resonator. In the regime with $\Omega_0$ comparableto the two-level transition frequency, "superradiant" quantum phase transitionsfor the cavity vacuum have been predicted, e.g. within the Dicke model. Here,we prove that if the time-independent light-matter Hamiltonian is considered, asuperradiant quantum critical point is forbidden for electric dipole atomictransitions due to the oscillator strength sum rule. In circuit QED, thecapacitive coupling is analogous to the electric dipole one: yet, such no-goproperty can be circumvented by Cooper pair boxes capacitively coupled to aresonator, due to their peculiar Hilbert space topology and a violation of thecorresponding sum rule.

Is there a no-go theorem for superradiant quantum phase transitions in cavity and circuit QED ?