Our paper on Can We Observe Nonperturbative Vacuum Shifts in Cavity QED? has been published in Physical Review Letters!

This work addresses a fundamental question: can the coupling of a single dipole to a strongly confined electromagnetic vacuum result in nonperturbative corrections to the dipole’s ground state?

We consider two simplified but generic cavity QED setups and derive analytic expressions for the total ground-state energy, carefully distinguishing between purely electrostatic and genuine vacuum-induced contributions. Importantly, our derivation takes the full electromagnetic spectrum into account while avoiding ambiguities from ad hoc mode truncation.

Our findings show that while confinement alone is insufficient for substantial vacuum-induced corrections, the presence of high-impedance modes such as plasmons or engineered LC resonances can drastically enhance these effects. This suggests that appropriately designed experiments could access a regime where light-matter interactions become nonperturbative.

This work was done in collaboration with Rocío Sáez Blázquez, Daniele de Bernardis and Peter Rabl from TU Vienna.