03 April 2009

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.

06 March 2009

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."

26 February 2009

          

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."

15 January 2009

Quantum effects in biosystems Discover Magazine In Discover (February 2009), Mark Anderson reviews contemporary experiments in biophysics that explore the influence of quantum effects in living systems: "Could quantum mechanisms be driving some of the most elegant and inexplicable processes of life? For years experts doubted it: Quantum phenomena typically reveal themselves only in lab settings, in vacuum chambers chilled to near absolute zero. Biological systems are warm and wet. Most researchers thought the thermal noise of life would drown out any quantum weirdness that might rear its head. Yet new experiments keep finding quan­­tum processes at play in biological systems, says Christopher Altman, alumni researcher from European futurist think tank Starlab. With the advent of powerful new tools like femtosecond (10-15 second) lasers and nanoscale-precision positioning, life’s quantum dance is finally coming into view."

The Unmanned Air Force USAF In Network World and concurrent Slashdot updates, Lt. Gen. Seip discusses the future of unmanned combat aerial vehicles. "How important have unmanned aircraft become to the US military? Well, how's this: the Air Force says next year it will acquire more unmanned aircraft than manned aircraft. Air Force Lt. Gen. Norman Seip this week said the service is "all in" when it comes to developing unmanned systems and aircraft.' Next year, the Air Force will procure more unmanned aircraft than manned aircraft,' the general said. 'I think that makes a very pointed statement about our commitment to the future of unmanned aircraft, and what it brings to the fight in meeting the requirements of combatant commanders.'"

15 November 2008

Convergence08  Mountain View  " From 15-16 November 2008 – the world's most dangerous ideas will collide in Mountain View, California. Convergence08 examines the world-changing possibilities of nanotechnology and the life-changing promises of biotechnology. It is the premier forum for debate and exploration of cognitive technology ethics – and ground zero of the past and future information technology revolution. Convergence08 is an innovative, lively 'unconference– the first and only unclassified forum dedicated solely to the convergence of NBIC – nano-, bio-, information and cognitive – technology developments.

As my own UNISCA First Committee chair report to the General Assembly – "Converging Technologies: The Future of the Global Information Society" – focused specifically upon these long-term technological and cultural challenges, which we will have to confront both as a society and as a species – I have high hopes that this meeting will provide a stimulating, and unparalleled, open venue for exploration of novel ideas, discussion of alternative paradigms, and fertile grounds for brainstorming original, innovative solutions. My congratulations to the initiative of the conference organizers. I look forward to reporting back upon conclusion of the conference, as there has been an open conference wiki set up at the conference website to contribute novel ideas to the discussion.

02 October 2008

Time in Quantum Mechanics Perimeter Institute The Clock and the Quantum focuses on conceptual and technical issues concerning the role of time in quantum theory – including quantum correlations in time, histories approaches, pre- and post-selected ensembles, time and quantum measurement, and causality under the framework of quantum theory. 

Lee Smolin discusses cosmological inflation, the problem of initial conditions, and the interpretation of the "wavefunction of the universe." Lev Vaidman provides a review of the two state vector formalism, which considers backwards-evolving quantum states. Noriyuki Hatakenaka presents a new scheme for testing macrorealism without statistical treatments by combining Leggett-Garg and Greenberger-Horne-Zeilinger (GHZ) inequalities, i.e. a temporal GHZ test using quantum correlations in time. Lucian Ionescu outlines an "upgrade" of the Feynman path integral formalism – where qubits, instead of complex amplitudes – are associated within elementary transitions of a causal network structure.

The conference is first in a series of foundations conferences organized under joint collaboration between the Perimeter Institute and three Australian national universities.

09 September 2008



From Qubits to Black Holes Technion | Macquarie University "Asher Peres (1934-2005), was an Israeli scientist who is widely considered to be one of the pioneering founders of quantum information science. A student of Nathan Rosen, (the “R” of EPR), Asher codiscovered quantum teleportation, a time-reversal test for quantum entanglement, and published numerous works on the foundations of quantum science. His research legacy continues through his many research collaborators, students, textbooks and research papers."

The Technion (Israel), and Macquarie University (Australia), will host the inaugural Asher Peres International Physics School 2008, for senior undergraduates and junior postgraduates in a series of lectures ranging from quantum mechanics, theory and experiments, through to quantum gravity. Held over five days, from November 17-22 (2008), in the historic environs at Chowder Bay on Sydney Harbor, the School will feature lectures from leading scientists from around the world, including Sir Peter Knight, Artur Ekert, Christian Kurtsiefer, Chris Fuchs, Bei Lok Hu, Jason Twamley, Daniel Terno, Gavin Brennen, Alexei Gilchrist, James Rabeau, and James Cresser.