Abstract
We consider theoretically a superconducting qubit–nanomechanical resonator (NR) system, which was realized by LaHaye et al. [Nature (London) 459, 960 (2009)]. First, we study the problem where the state of the strongly driven qubit is probed through a frequency shift of the low-frequency NR. In the case where the coupling is capacitive, the measured quantity can be related to the so-called quantum capacitance. Our theoretical results agree with the experimentally observed result that, under resonant driving, the frequency shift repeatedly changes sign. We then formulate and solve the inverse Landau-Zener-Stückelberg problem, where we assume the driven qubit's state to be known (i.e., measured by some other device) and aim to find the parameters of the qubit's Hamiltonian. In particular, for our system the qubit's bias is defined by the NR's displacement. This may provide a tool for monitoring of the NR's position.
- Received 17 October 2011
DOI:https://doi.org/10.1103/PhysRevB.85.094502
©2012 American Physical Society