Flux Qubit Readout in the Persistent Current Basis at arbitrary Bias Points

Abstract

Common flux qubit readout schemes are qubit dominated, meaning they measure in the energy eigenbasis of the qubit. For various applications meausrements in a basis different from the energy eigenbasis are required. Here we present an indirect measurement protocol, which is detector dominated instead of qubit dominated, yielding a projective measurements in the persistent current basis for arbitrary bias points. We show that with our setup it is possible to perform a quantum nondemolition measurement (QND) in the persistent current basis at all flux bias points with fidelities reaching almost 100%.