∂-wave throws down the gauntlet Vancouver Pending third-party referee, peer review or independent verification, D-Wave's press release has been received with expected enthusiasm in the mainstream press and restrained skepticism in the scientific community. "I'll be a bit of a skeptic until I see what they have done. I'm happy these guys are doing it. But the proof of the pudding is in the eating." – Seth Lloyd

Nondemolition measurement. a) Schematic representation of the qubit excitation pulse (top) and readout pulse (bottom) sequence; b) Probability to detect the oscillator in state h for qubit states; c) Measurement of Rabi oscillations; d) Parameters characterizing measurement errors. Lupascu et al. Nature Physics, 14 January 2007.

Quantum non-demolition measurement of a superconducting two-level system Delft|NTT By minimizing disturbance to the system under investigation, quantum nondemolition measurement (QND) can provide particularly clear signatures of quantum coherence. In Nature Physics and cond-mat 0611505, Lupascu et al. demonstrate nondemolition measurement of superconducting qubits coupled to a nonlinear resonator. "The high correlation between measurement results demonstrates the quantum nondemolition nature of the readout method. The fact that quantum nondemolition measurement is possible for superconducting qubits strengthens the notion that these fabricated mesoscopic systems are to be regarded as fundamental quantum objects. Our results are also relevant for quantum information processing protocols such as state preparation and error correction. " cf. also Kavli Institute announcement in TU Delta (in Dutch).

High-speed linear optics quantum computing using active feed-forward measurement Vienna In Nature 445, 65-69 and concurrent press summary, Zeilinger's group reports experimental demonstration of feedforward error correction via one-way, highly-entangled cluster states in linear optics. "With present technology, the individual computational step can be operated in less than 150 ns using electro-optical modulators. This is an important result for the future development of one-way quantum computers, whose large-scale implementation will depend on advances in the production and detection of the required highly entangled cluster states."



Retrocausal Signaling UW Via the Pontiff – John Cramer recently conducted a UW seminar outlining recent progress on his plans for an experimental test of retrocausal signaling using entangled photon pairs, notwithstanding Eberhard's theorem. The planned experiment draws upon the thesis of Birgit Dopfer (Zeilinger group, Universität Wien), Wheeler-Feynman theory and Cramer's own transactional interpretation. Concurrent press summary and diagram of the setup are available via SF Gate. cf. also Cramer's online summary of the proposed experiment, Jensen gedanken, double-slit and delayed choice quantum eraser experiments (refs: serafino).

Quantum Transport in Carbon Nanotubes » links – Condensed matter physics weblog metadatta appended to links. Recent post topics include the Wolf Prize announcement in spintronics and single-quantum dot nanowire light-emitting diodes.