Basing on SR 4-terminal SQUID, a fully superconducting detector of a flux qubit states id proposed. Absence of high-frequency and quasiparticle current in the qubit-measuring circuit weakly coupled with the qubit provides little back action and prevents fast qubit decoherencing durin weak continuous measurements of quantum states.
O. G. Turutanov, V. I. Shnyrkov, A. N. Omelyanchouk
Stochastic amplifier based on superconducting interferometer with 4-terminal Josephson junction for flux qubit readout.
MSMW’07 Symposium Proceedings, Kharkov, Ukraine, p.822-824