First use of Deutsch's Algorithm in a cluster state quantum computer

Apr 18, 2007 By Miranda Marquit feature
First use of Deutsch's Algorithm in a cluster state quantum computer
Quantum computer set up. Image credit: Mark Tame.

Finding a way to build a quantum computer that works more efficiently than a classical computer has been the holy grail of quantum information processing for more than a decade. “There is quite a strong competition at the moment to realize these protocols,” Mark Tame tells PhysOrg.com.

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.

Explore further: Sensitive detection method may help impede illicit nuclear trafficking

add to favorites email to friend print save as pdf

Related Stories

The Spin Doctor

Jan 13, 2011

An electron spin can be compared to the needle of a compass that points either north or south. Some electrons in a full shell point up, canceling out the electromagnetic fields of an equal number of electrons ...

Recommended for you

Device turns flat surface into spherical antenna

Apr 14, 2014

By depositing an array of tiny, metallic, U-shaped structures onto a dielectric material, a team of researchers in China has created a new artificial surface that can bend and focus electromagnetic waves ...

User comments : 0

More news stories

CERN: World-record current in a superconductor

In the framework of the High-Luminosity LHC project, experts from the CERN Superconductors team recently obtained a world-record current of 20 kA at 24 K in an electrical transmission line consisting of two ...

Glasses strong as steel: A fast way to find the best

Scientists at Yale University have devised a dramatically faster way of identifying and characterizing complex alloys known as bulk metallic glasses (BMGs), a versatile type of pliable glass that's stronger than steel.

ESO image: A study in scarlet

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41. In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that ...

First direct observations of excitons in motion achieved

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton movement within ...

Warm US West, cold East: A 4,000-year pattern

Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, ...

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...