Speakers:
Cesar A. Rodriguez-Rosario
Authors:
Cesar A. Rodriguez-Rosario, James D. Whitfield, Alan Aspuru-Guzik
We introduce the quantum stochastic walk (QSW), which determines the evolution of generalized quantum mechanical walk on a graph that obeys a quantum stochastic equation of motion. Using an axiomatic approach, we specify the rules for all possible quantum, classical and quantum-stochastic transitions of a vertex as defined from its connectivity. We show how the family of possible QSW encompasses both the classical random walk (CRW) and the quantum walks (QW) as special cases, but also includes more general probability distributions.
Submitted by
Carod on Wed, 20/05/2009 - 19:08.
A Research Fellow is to be appointed at Birmingham, to start by October 2009, on my EPSRC project to apply techniques of geometric logic to the topos approaches to quantum theory (Isham and Doering at Imperial, Landsman's group at Nijmegen).
The job is now posted online at Birmingham, application deadline 10th June 2009; go to http://www.hr.bham.ac.uk/jobs/ and search by post number 43408. There will be an advertisement on http://www.jobs.ac.uk/ shortly.
You can also find all that information on my website at
http://www.cs.bham.ac.uk/~sjv/geophysics.php
Authors:
Dave Bacon and Steven T. Flammia
The difficulty in producing precisely timed and controlled quantum gates is a significant source of error in many physical implementations of quantum computers. Here we introduce a simple universal primitive, adiabatic gate teleportation, which is robust to timing errors and many control errors and maintains a constant energy gap throughout the computation above a degenerate ground state space. Notably this construction allows for geometric robustness based upon the control of two independent qubit interactions.
Submitted by
Sflammia on Tue, 19/05/2009 - 17:45.
Submitted by
Editor on Wed, 13/05/2009 - 09:24.
QD Vision, based in Watertown, MA, is promoting a new LED-based lamp that it made with Nexxus Lighting of Charlotte, NC. Nexxus makes a lamp designed to screw into standard sockets used in recessed ceiling lighting. It consists of an array of white-light LEDs encircled by fins that remove excess heat. QD Vision adds an optic--a plastic cover with a special coating that snaps into place over the LEDs. It's that coating that makes the difference in the quality of the light.
Submitted by
Editor on Fri, 08/05/2009 - 07:03.
A team of physicists from Austria has sent pairs of entangled photons, which can be used to encrypt messages with complete security, between telescopes spaced 144km apart in the Canary Islands. The researchers say that preserving entanglement over this distance shows the feasibility of carrying out quantum cryptography using a worldwide network of satellites.
Authors:
M. B. Plenio and S. Virmani
We consider the possibility of adding noise to a quantum circuit to make it efficiently simulatable classically. In previous works this approach has been used to derive upper bounds to fault tolerance thresholds - usually by identifying a privileged resource, such as an entangling gate or a non-Clifford operation, and then deriving the noise levels required to make it `unprivileged'. In this work we consider extensions of this approach where noise is added to Clifford gates too, and then `commuted' around until it concentrates on attacking the non-Clifford resource.
Submitted by
Virmani on Mon, 27/04/2009 - 15:33.
Authors:
Neil P. Oxtoby, Ángel Rivas, Susana F. Huelga, and Rosario Fazio
We consider non-interacting multi-qubit systems as controllable probes of an environment of defects/impurities modelled as a composite spin-boson environment. The spin-boson environment consists of a small number of quantum-coherent two-level fluctuators (TLFs) damped by independent bosonic baths. A master equation of the Lindblad form is derived for the probe-plus-TLF system.
Submitted by
Burgarth on Mon, 27/04/2009 - 13:29.
Authors:
V. B. Scholz and R. F. Werner
The situation of two independent observers conducting measurements on a joint quantum system is usually modelled using a Hilbert space of tensor product form, each factor associated to one observer. Correspondingly, the operators describing the observables are then acting non-trivially only on one of the tensor factors. However, the same situation can also be modelled by just using one joint Hilbert space, and requiring that all operators associated to different observers commute, i.e. are jointly measurable without causing disturbance.
Submitted by
Burgarth on Mon, 27/04/2009 - 13:23.
Submitted by
Editor on Thu, 23/04/2009 - 10:02.
Researchers at the National Institute of Standards and Technology (NIST) have proved, for the first time, that the lifetime of quantum-computing bits can be extended. In their experiment, they showed that by applying specially timed magnetic pulses to qubits, made of beryllium ions, they could prolong the life of the quantum bits from about one millisecond to hundreds of milliseconds. The work is described in this week's Nature.
Submitted by
Editor on Tue, 14/04/2009 - 10:29.
The realization of a universal quantum computer that can carry out arbitrary computations remains a long term goal. But the technologies developed so far enable us to perform so called quantum simulations. Here assemblies of directly controllable quantum particles form models for complex systems which are difficult to manipulate. A new, promising technique was now developed in the group of Professor Gerhard Rempe at the Max Planck Institute of Quantum Optics in Garching.
Pages
