Ultrastrong coupling regime of cavity QED with phase-biased flux qubits

By J. Bourassa, Jay M. Gambetta, A. A. Abdumalikov, O. Astafiev, Yasunobu Nakamura, Alexandre Blais. 2009

198 citations recorded by the source corpus.

We theoretically study a circuit QED architecture based on a superconducting flux qubit directly coupled to the center conductor of a coplanar waveguide transmission-line resonator. As already shown experimentally [A. A. Abdumalikov, Jr. et al., Phys. Rev. B 78, 180502(R) (2008)], the strong coupling regime of cavity QED can readily be achieved by optimizing the local inductance of the resonator in the vicinity of the qubit. In addition to yielding stronger coupling with respect to other proposals for flux qubit based circuit QED, this approach leads to a qubit-resonator coupling strength $g$ which does not scale as the area of the qubit but is proportional to the total inductance shared between the resonator and the qubit. Strong coupling can thus be attained while still minimizing sensitivity to flux noise. Finally, we show that by taking advantage of the large kinetic inductance of a Josephson junction in the center conductor of the resonator can lead to coupling energies of several tens of percent of the resonator frequency, reaching the ultrastrong coupling regime of cavity QED where the rotating-wave approximation breaks down. This should allow an on-chip implementation of the $E\ensuremath{\bigotimes}\ensuremath{\beta}$ Jahn-Teller model.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/82bf63deb4bd43ac6302c079e9dba2e8b2ebc56a

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Citations in the corpus

Circuit quantum electrodynamics in the ultrastrong-coupling regime (2010, background): “We reach remarkable normalized coupling rates g / ω r of up to 12p by enhancing the inductive couplin”
Microwave photonics with superconducting quantum circuits (2017, methodology): “Circuit-QED systems in the USC regime can also be used for simulations of the Jahn-Teller model [404, 479, 480] and exploration of symmetry-breaking quantum vacuum, which is analogous to the Higgs mechanism [439].”