We report the parametric amplification of a microwave signal in a Kerr medium formed from superconducting qubits. Two mutually coupled flux qubits, embedded in the current antinode of a superconducting coplanar waveguide resonator, are used as a nonlinear element. Shared Josephson junctions provide the qubit-resonator coupling, resulting in a device with a measured gain of about 20 dB. We argue, that this arrangement represents a unit cell which can be straightforwardly extended to a quasi one-dimensional quantum metamaterial with a large tunable Kerr nonlinearity.
@article{arxiv.1312.7237,
title = {Parametric amplification by coupled flux qubits},
author = {M. Rehak and P. Neilinger and M. Grajcar and G. Oelsner and U. Hubner and E. Ilichev and H. -G. Meyer},
journal= {arXiv preprint arXiv:1312.7237},
year = {2015}
}