Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Fundamental limitation to quantum computers

Abstract:
Quantum computers that store information in so-called quantum bits (or qubits) will be confronted with a fundamental limitation. This is the claim made by Dutch theoretical physicists from the Foundation for Fundamental Research on Matter (FOM) and Leiden University in an article recently published in the journal Physical Review Letters.

Fundamental limitation to quantum computers

July 07, 2005

A quantum computer can only function if the information exists for long enough to be processed. The so-called coherence of the qubit ensures that the quantum information remains intact. The researchers have now discovered that the coherence spontaneously disappears over the course of time and with this the stored information as well. This could pose a considerable problem for the development of a quantum computer.

Electron microscope image of a qubit from Hans Mooij's research group at Delft University of Technology
Electron microscope image of a qubit from Hans Mooij's research group at Delft University of Technology. Copyright Delft University of Technology.
Click image for larger version.

A quantum computer makes use of the fact that a quantum mechanical system -an electron, an atom or even a larger system such as a superconducting quantum bit - can simultaneously exist in two states. Normally one of the two states disappears as soon as the system comes into contact with the outside world. The coherence then disappears as a result of the decoherence process and the information in a quantum bit is lost.

A quantum bit typically consists of a large number of particles, with an unavoidably large number of possibilities to be influenced by the environment and thus be subjected to decoherence. Jasper van Wezel, Jeroen van den Brink (FOM) and Jan Zaanen, all attached to the Lorentz Institute of Leiden University have now investigated whether it is possible to maintain the coherence in an isolated qubit.

Much to their surprise they discovered that the coherence tends to spontaneously disappear, even without external influences. The degredation process is linked to the occurrence of quantum mechanical spontaneous symmetry breaking. In classical physics an equivalent example of this process is spontaneous crystallisation in a solution. At a certain position a crystal is spontaneously formed, as a result of which the fluid structure is broken.

According to the researchers' predictions, the coherence in some highly promising concepts for qubits will disappear after about a second. Moreover, the smaller the qubits the faster that process occurs. All of this would seem to pose a fundamental limitation on the development of qubits. Experimental research will now have to demonstrate whether this phenomenon actually occurs.


####


The article "An Intrinsic Limit to Quantum Coherence due to Spontaneous Symmetry Breaking" was published in Physical Review Letters, in the week ending 17 June 2005.

Contact:
Dr Jeroen van den Brink
+31 (0)71 527 5510
brink@lorentz.leidenuniv.nl

Copyright Netherlands Organisation for Scientific Research

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Foundation for Fundamental Research on Matter

Related News Press

Quantum Computing

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

First on-chip nanoscale optical quantum memory developed: Smallest-yet optical quantum memory device is a storage medium for optical quantum networks with the potential to be scaled up for commercial use September 11th, 2017

High-speed quantum memory for photons September 9th, 2017

Quantum detectives in the hunt for the world's first quantum computer September 8th, 2017

Announcements

Band Gaps, Made to Order: Engineers create atomically thin superlattice materials with precision September 26th, 2017

Assembly of nanoparticles proceeds like a zipper: Viruses and nanoparticles can be assembled into processable superlattice wires according to scientists from Aalto University Finland September 25th, 2017

Enhancing the sensing capabilities of diamonds with quantum properties: A simple method can give diamonds the special properties needed for quantum applications such as sensing magnetic fields September 24th, 2017

Quantum twisted Loong confirms the physical reality of wavefunctions September 23rd, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project