Martinis Rescues Schrödinger's Cat UCSB In follow-up to Phys Rev Lett 97, 166805 (2006) , " Undoing a Weak Quantum Measurement of a Solid-State Qubit," New Scientist is reporting on upcoming experimental plans to save Schrödinger's Cat from environmental decoherence.
" We propose an experiment which demonstrates the undoing of a weak continuous measurement of a solid-state qubit, so that any unknown initial state is fully restored. Measurement undoing, or "quantum undemolition," may be interpreted as a kind of quantum eraser, in which the information obtained from the first measurement is erased by the second measurement. The experiment can be realized using charge or superconducting phase qubits."
Reversible weak measurement holds security implications for the integrity of present-day quantum cryptography protocols. " This could be a very profound discovery. Since the birth of quantum theory we have become used to thinking of quantum measurements as creating reality: until things are measured, they don't have an absolute, independent existence. But if some forms of measurement, such as weak measurement, are reversible, then the fundamentals of quantum mechanics go even deeper than we realised. If you create reality with weak quantum measurements, does undoing them erase the reality you created?"
Asian Conference on Quantum Information Science Kyoto, 03-06 Sep 2007 The AQIS07 Meeting will focus on quantum information science and technology. This is a new interdisciplinary field that bridges quantum physics, computer science, mathematics, and computing technologies. AQIS07, following tradition, will consist of invited talks and selected oral communications and posters. Contributions for short communications and posters will be solicited in research areas that relate to quantum information science and technology, both theory and experiments. This includes, but is not limited to: quantum automata, algorithms and complexity, quantum cryptography, quantum information theory, quantum entanglement, non-locality, quantum error correction, decoherence-free subspaces, quantum optics, NMR and solid-state technologies, quantum processor design, quantum programming languages and semantics."
Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems Berkeley Lab In Nature 446, 782-786, Fleming et al. report on coherent electron transfer in photosynthetic complexes. " We have obtained the first direct evidence that remarkably long-lived wavelike electronic quantum coherence plays an important part in energy transfer processes during photosynthesis. This wavelike characteristic can explain the extreme efficiency of the energy transfer, because it enables the system to simultaneously sample all the potential energy pathways and choose the most efficient one. " Covered also in Scientific American, Wired, PhysicsWeb, rose.blog.
Tunneling and green tea J Am Chem Soc 129 (18) pp 5846 - 5854 " Tunneling is a ubiquitous phenomenon in nature. We had a problem understanding how polyphenols work at such low concentrations. This paper gives theoretical credence to a large amount of experimental evidence of polyphenols as in vitro and in vivo antioxidants."
Solid-State Qubits with Tunable Coupling NEC|JST|RIKEN In Science 314, 5804, NEC, JST and RIKEN report on tunable coupling between two flux qubits through mutual inductance with a dc SQUID acting as a nonlinear transformer. " ... the research group devised an original mechanism that employs another qubit in between the two qubits for coupling. The coupling qubit is able to turn on and off the magnetic coupling between the two qubits. Control is achieved simply by inputting a microwave. Moreover, coupling operation has been achieved without shortening the lifetime of each qubit." Critical analysis and discussion at Technology Review, rose.blog, nextquant [1] and [2], Scott Aaronson, and Travis Hime on related experiments at Berkeley.
Refuting Nonlocal Realism In Nature 446 (871 - 875) and concurrent arXiv preprint, Zeilinger et al. refute nonlocal quantum realism in experiments with entangled photon pairs. " We measure previously untested correlations between two entangled photons, and show that these correlations violate an inequality proposed by Leggett for nonlocal realistic theories. Our result suggests that giving up the concept of locality is not sufficient to be consistent with quantum experiments – unless certain intuitive features of realism are abandoned. " Via Nature, Scientific American, Quantum Quandaries.
Experimental Realization of Deutsch's Algorithm in a One-Way Quantum Computer Belfast|Vienna In Phys Rev Lett 98, 140501 and concurrent preprint coverage in quant-ph/0611186, PhysOrg, Tame, Zeilinger et al. report on the first experimental demonstration of an all-optical, one-way implementation of Deutsch's quantum algorithm on a four-qubit cluster state. " Experimental results are in excellent agreement with the theoretical model, therefore demonstrating the successful performance of the algorithm."
Experimental implementation of Deutsch's algorithm in a cluster-state quantum computer Tame, Zeilinger et al. Phys Rev Letters 98, 140501 (2007) . (a) Experimental setup. An ultraviolet pump-laser performs two passages through a nonlinear crystal aligned to produce entangled photon pairs. (b) Sketch of the cluster-state configuration. (c) and (d) Real and Imaginary plots of the reconstructed experimental density matrix.
New links in quantum information processing [1] nextquant Recent topics include d-Wave, Top 5 Urban Legends in Quantum Computing, Superconducting Quantum Computing: d-Wave replies on NEC, The Awful Truth about Schrödinger’s Cat. [2] Strange Paths on physics, computation, philosophy – electron flow paths, escaping from the end of the universe, the quantum eraser experiment.
