Generation and control of Greenberger-Horne-Zeilinger entanglement in superconducting circuits RIKEN In quant-ph 0510169, Wei, Liu, and Nori propose an efficient approach to generate and control quantum entanglement between three macroscopic coupled superconducting qubits. "By conditionally rotating, one by one, selected Josephson charge qubits, we show that their Greenberger-Horne-Zeilinger (GHZ) entangled states can be deterministically generated. The possibility of using the prepared GHZ correlations to test the macroscopic conflict between the noncommutativity of quantum mechanics and the commutativity of classical physics is also discussed."
Coherent State Evolution in a Superconducting Qubit from Partial-Collapse Measurement UCSB Martinis et al, Science 312, 5779. "Measurement is one of the fundamental building blocks of quantum-information processing systems. Partial measurement, where full wavefunction collapse is not the only outcome, provides a detailed test of the measurement process. We introduce quantum-state tomography in a superconducting qubit that exhibits high-fidelity single-shot measurement. For the two probabilistic outcomes of partial measurement, we find either a full collapse or a coherent yet nonunitary evolution of the state. This latter behavior explicitly confirms modern quantum-measurement theory and may prove important for error-correction algorithms in quantum computation."
Flux qubit decoherence sources RIKEN, VTT, NEC In cond-mat 0606481, Yoshihara, Harrabi, Niskanen, Nakamura and Tsai investigate flux qubit decoherence sources, demonstrating an optimal bias condition at which noise sources are well decoupled and coherence time is primarily limited by energy relaxation of the qubit.