Effects of quasiparticle tunnelling in a circuit-QED realization of a strongly driven two-level system
Journal article, 2013

We experimentally and theoretically study the frequency shift of a driven cavity coupled to a superconducting charge qubit. In addition to previous studies, here we also consider drive strengths large enough to energetically allow for quasiparticle creation. Quasiparticle tunnelling leads to the inclusion of more than two charge states in the dynamics. To explain the observed effects, we develop a master equation for the microwave dressed charge states, including quasiparticle tunnelling. A bimodal behaviour of the frequency shift as a function of gate voltage can be used for sensitive charge detection. However, at weak drives, the charge sensitivity is significantly reduced by nonequilibrium quasiparticles, which induce transitions to a non-sensitive state. Unexpectedly, at high-enough drives, the quasiparticle tunnelling enables a very fast relaxation channel to the sensitive state. In this regime, the charge sensitivity is thus robust against externally injected quasiparticles and the desired dynamics prevail over a broad range of temperatures. We find very good agreement between the theory and experiment over a wide range of drive strengths and temperatures.

relaxation

dynamics

quantum

Author

Juha Leppäkangas

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Sebastian Erik de Graaf

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Astghik Adamyan

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Mikael Fogelström

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Andrey Danilov

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Tobias Lindström

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Sergey Kubatkin

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Göran Johansson

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Journal of Physics B: Atomic, Molecular and Optical Physics

0953-4075 (ISSN)

Vol. 46 22 Art. no. 224019-

Subject Categories

Atom and Molecular Physics and Optics

DOI

10.1088/0953-4075/46/22/224019

More information

Created

10/6/2017