Dwave Systems researchers have written a paper describing a novel rf-SQUID flux qubit. It is robust against fabrication variations in Josephson junction critical currents and device inductance has been implemented. Experimental results were shown to be in agreement with
predictions of a quantum mechanical Hamiltonian whose parameters were independently calibrated, thus justifying the identification of this device as a flux qubit.
22 page pdf: Experimental Demonstration of a Robust and Scalable Flux Qubit
Three key conclusions:
1) the CCJJ rf-SQUID is a robust and scalable device in that it allows for in-situ correction for parametric variations in Josephson junction critical currents and device inductance, both within and between flux qubits using only static flux biases.
2) the measured flux qubit properties, namely the persistent currentvand tunneling energy q, agree with the predictions of a quantum mechanical Hamiltonian whose parameters have been independently calibrated, thus justifying the identification of this device as a flux qubit.
3) it has been experimentally demonstrated that the low frequency flux noise in this all Nb wiring flux qubit is comparable to the best all Al wiring devices reported upon in the literature. Taken in summation, these three conclusions represent a significant step forward in the development of useful large scale superconducting quantum information processors.