Quantum analysis of a nonlinear microwave cavity-embedded dc SQUID displacement detector
Abstract
We carry out a quantum analysis of a dc SQUID mechanical displacement detector, comprising a SQUID with mechanically compliant loop segment, which is embedded in a microwave transmission line resonator. The SQUID is approximated as a nonlinear, current dependent inductance, inducing an external flux tunable, nonlinear Duffing self-interaction term in the microwave resonator mode equation. Motion of the compliant SQUID loop segment is transduced inductively through changes in the external flux threading SQUID loop, giving a ponderomotive, radiation pressure type coupling between the microwave and mechanical resonator modes. Expressions are derived for the detector signal response and noise, and it is found that a soft-spring Duffing self-interaction enables a closer approach to the displacement detection standard quantum limit, as well as cooling closer to the ground state.
Cite
@article{arxiv.0806.4171,
title = {Quantum analysis of a nonlinear microwave cavity-embedded dc SQUID displacement detector},
author = {P. D. Nation and M. P. Blencowe and E. Buks},
journal= {arXiv preprint arXiv:0806.4171},
year = {2009}
}