National Workshop on Quantum Information Science OSTP|NTSC Via John Preskill, Dave Bacon, Ian Durham and Scott Aaronson — NSTC has announced a workshop in response to the recent Federal Vision for Quantum Information Science: "In January 2009, the United States National Science and Technology Council issued the report A Federal Vision for Quantum Information Science. The report proposes that

“The United States … create a scientific foundation for controlling, manipulating, and exploiting the behavior of quantum matter, and for identifying the physical, mathematical, and computational capabilities and limitations of quantum information processing systems in order to build a knowledge base for this 21st century technology.”

This Workshop on Quantum Information Science (QIS) has been organized in response to the NSTC report. It brings together leading theorists and experimenters drawn from physical science, computer science, mathematics, and engineering who will assess recent progress in QIS and identify major goals and challenges for future research."

Adaptive quantum networks – We introduce a robust, error-tolerant adaptive training algorithm for generalized learning in high-dimensional, superposed quantum networks, or adaptive quantum networks. The formalized procedure applies standard backpropagation training to a coherent ensemble of discrete topological configurations of individual neural networks, each of which is formally merged under linear superposition. Quantum parallelism facilitates simultaneous training and revision within this coherent state space, resulting in accelerated convergence to optima. The protocol provides quantitative, numerical indicators for optimization of both single-neuron activation functions and reconfiguration of global network topology.

Density plot of qubit purity ξ after t =20 kicks as a function of chaos parameter K=kT and nonlinear parameter g for T=2, δ=0.2 and ε=0.5.

Chaotic dynamics of a Bose-Einstein condensate coupled to a qubit Shepelyansky, Martin, Georgot arXiv 0812.5067: "We study the coupling between a qubit and a Bose-Einstein condensate moving in a kicked optical lattice. In the regime where BEC size is smaller than the lattice period, the chaotic dynamics of the BEC is effectively controlled by the qubit state. This gives an example of exponentially sensitive control over a macroscopic state by internal qubit states. The realization of such coupled systems is within reach of current experimental techniques."

Interference of interacting matter waves Innsbruck arXiv 0812.4836: "The phenomenon of matter wave interference lies at the heart of quantum physics. It has been observed in various contexts in the limit of non-interacting particles as a single particle effect. Here we observe and control matter wave interference whose evolution is driven by interparticle interactions. In a multi-path matter wave interferometer, the macroscopic many-body wave function of an interacting atomic Bose-Einstein condensate develops a regular interference pattern, allowing us to detect and directly visualize the effect of interaction-induced phase shifts. We demonstrate control over the phase evolution by inhibiting interaction-induced dephasing, and by refocusing a dephased macroscopic matter wave in a spin-echo type experiment. Our results show that interactions in a many-body system lead to a surprisingly coherent evolution – possibly enabling narrow-band and high-brightness matter wave interferometers based on atom lasers."

          

Entanglement made Visible Genève In arXiv 0902.2896 and arXivblog summary, Gisin et al. show that macroscopic entanglement – and Bell inequality violations – can be made directly visible to the human retina. "We have shown that quantum experiments with human eyes as detectors appear possible, based on a realistic model of the eye as a photon detector. Entanglement, in principle, can be seen."

The Case for a National Investment: A Policy Essay for the Obama Transition Office In a recent CCC white paper, Aaronson and Bacon present the case for quantum computing as a national mandate. "First, quantum computing must be considered a national security issue. Since quantum computers break the codes used ubiquitously to protect transactions over the Internet, any country obtaining a scalable quantum computer would have the ability to disrupt electronic communication. Second, quantum information science research will help to maintain the US's scientific and technological advantages. Third, quantum computing is the study of the fundamental limits of computing and, as such, offers the potential to revolutionize our understanding of computation itself."

Pentagon explores quantum biology DARPA/DSO has launched a research initiative to investigate quantum mechanical effects in biological systems [initial Wired announcement, Sep. 2008]. "Scientists have recently discovered that quantum energy transfers allow plants and cynobacteria to convert sunlight into chemical energy nearly instantly, and with almost 100 percent efficiency. As energy passes between molecules involved in photosynthesis, a newly-observed 'wavelike characteristic' allows the energy to 'simultaneously sample all the potential energy pathways and choose the most efficient one.' DARPA says there are other biological examples of quantum effects — including an explanation, perhaps, for how birds are able to navigate along the Earth's magnetic fields."