The latest experiment performed as a collaboration by a Queen’s University theoretical group and an experimental group in Vienna has “allowed us to pick up the pace” of quantum computing.
The joint project’s experiment is reported in Physical Review Letters in an article titled, “Experimental Realization of Deutsch’s Algorithm in a One-Way Quantum Computer.”
“This is the first implementation of Deutsch’s Algorithm for cluster states in quantum computing,” Tame explains. Tame along with members of the Queen’s group in Belfast, including Mauro Paternostro and Myungshik Kim joined a group from the University of Vienna, including Robert Prevedel, Pascal Böhi, and Anton Zeilinger (who is also associated with the Institute for Quantum Optics and Quantum Information at the Austrian Academy of Sciences) to perform this experiment.
“When performing a quantum algorithm,” says Tame, “the standard approach is based on logical gates that are applied in a network similar to classical computing.” Tame points out that this method of quantum computing is not practical or efficient. “Our quantum computer model uses cluster states, which are highly entangled multi-partite quantum states.” The Irish and Austrian group’s quantum computer makes use of four entangled photons in a cluster state. Tame explains how it works:
“Our setup is completely based on light, where quantum information is encoded on each photon. The information is in the polarization of each photon, horizontal or vertical, and superpositions in between. An ultra-violet laser pumps a crystal and produces an entangled pair of photons in one direction. The laser beam then hits a mirror and bounces back to form another pair of entangled photons on its second passage through the crystal. These four photons are then made to interact at beamsplitters to form the entangled cluster state resource on which we perform the quantum computation.”
Next, Tame says, come the calculations. “We perform Deutsch’s Algorithm as a sequence of the measurements. When you measure in a specific basis, you can manipulate the quantum information in the photons using their shared entanglement.” He continues with an illustration related to classical computing: “You can think of the cluster state as the ‘hardware’, and the measurements as the ‘software’.”
Now that the groups in Belfast and Vienna have proved that Deutsch’s Algorithm works for a cluster-based quantum computer, the next step is to apply it to larger systems. “Right now it’s really just a proof of principle,” explains Tame. “We’ve shown it can be done, but we need to build larger cluster states and perform more useful computations.”
Tame admits that this next step is where it gets trickier. “Quantum systems like this can be influenced by small fluctuations in the environment. It can be difficult to get accurate computations using larger resources.” He says that noise resistant protocols need to be developed in order to maintain the coherence of the quantum information. “There’s not a lot of noise in the lab during the implementation of experiments on small numbers of qubits. But as we increase this number there are physical and technological concerns that need to be solved. This is a key issue.”
And does Tame have any idea how to solve some of these issues? “We have some schemes at the moment. It’s a work in progress.” He pauses. “But for now it’s exciting to have this proof that quantum computing can be efficiently performed with Deutsch’s Algorithm.”
Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.
Related stories:
First reported video of cell's recognition of danger through its protein response
(PhysOrg.com) -- Cells are expected to respond defensively when an antigen lands on a cell membrane and prepares to cause mischief.
Simulations may explain nanoparticles 'pinned' to graphene
It was hard to understand how a graphene sheet — a featureless, flat sheet of carbon atoms — lying on an equally featureless iridium surface, somehow converted itself into a kind of muffin tin that formed “muffins” made from newly arrived iridium atoms. The muffins were equally spaced and of equal size.
Physicists discover gold can be magnetic on the nanoscale
Physicists at the Georgia Institute of Technology have made important findings regarding gold on the nanoscale. They found that applying an electrical field on a surface-supported gold nanocluster changes its structure from a three-dimensional one to a planar flat structure. In another paper, they relate their discovery that gold in this size regime can be made magnetic through oxygenation of gold nanowires.
Aromaticity may occur in unexpected materials
Shiv Khanna, Ph.D., professor of physics, and colleagues from Virginia Commonwealth University and Penn State, were recently highlighted in the Editor’s Choice section of the journal
Science, as well as the trade publication Chemical & Engineering News, for the group’s work on the synthesis of an unusual inorganic ring molecule made of arsenic and tellurium, As
2Te
2-2, found to have magnetic and aromatic characteristics.
Researchers Demonstrate Quantum Teleportation and Memory in Tandem
In research that may be a key step toward real-life quantum communication—the transmission of information using atoms, photons, or other quantum objects—researchers created an experiment in which a quantum bit of information is transported across a distance of seven meters and briefly stored in memory. This is the first time that both quantum memory and teleportation, as the information transfer is known, have been demonstrated in a single experiment.
Quantum Communication Over Flawed Networks may be Possible
If successfully implemented, quantum communication could be an extremely secure method of transmitting information – but there are major roadblocks to pass. Recently, physicists suggested a way, at least in theory, to overcome perhaps the biggest of these problems: making quantum communication possible over “real life” networks with serious imperfections, such as leakage, and across distances greater than 10 kilometers.
IBM's Blue Gene Pulls Away from the Pack
IBM’s Blue Gene/L supercomputer sprinted to a new world record as it continued its four-year domination of the official TOP500 Supercomputer Sites list. The world’s fastest computer at Lawrence Livermore National Laboratory in California is now nearly three times faster than the rest of the pack.
Research predicts size-induced transition to nanoscale half-metallicity
How big does a cluster of metal atoms actually have to be before it starts acting like a metal: ductile, malleable and a conductor?
