Home  |  Top News  |  Most Popular  |  Video  |  Multimedia  |  News Feeds  |  Feedback
  Medicine  |  Nature & Earth  |  Biology  |  Technology & Engineering  |  Space & Planetary  |  Psychology  |  Physics & Chemistry  |  Economics  |  Archaeology
Top > Technology & Engineering > Contextuality Puts the 'Magic' in… >
Contextuality Puts the 'Magic' in Quantum Computing

Published: June 11, 2014.
By Canadian Institute for Advanced Research
http://www.cifar.ca

A new theoretical advance explains where the power of quantum computation comes from, and will help researchers design and build better computers and algorithms.

The strange properties of quantum mechanics give quantum computers the potential to perform some computations exponentially faster than conventional computers. But where the extra power comes from – and how best to take advantage of it – is in many ways still an open question.

A new paper in the journal Nature by CIFAR Fellow Joseph Emerson of the program in Quantum Information Science, along with colleagues at the Institute of Quantum Computing at the University of Waterloo, is a step towards solving the questions.

The paper shows that a quantum property called contextuality is the key. Contextuality refers to the fact that in quantum systems, a measurement will necessarily affect the thing being measured. For instance, if you want to measure the spin of a particle, it's wrong to think that there is a "real" spin just waiting to be revealed. Instead, the very act of measuring the spin helps determine what it will be.

"One way of thinking about contextuality is that inevitably measurements involve some kind of disturbance. I'm not just learning about some definite property the system had prior to the measurement. I can be learning about some property the system had, but only in a way that depends on how I did the measurement."

One of the leading approaches for quantum computing uses a technique called fault-tolerant stabilizer computation. It's a way of correcting errors that occur in quantum computers as the quantum states interact with the environment. By using a process called "magic-state distillation," quantum computers can be made to function dependably despite the noise introduced by the environment.

Emerson's paper shows that the only kinds of "magic states" that will yield quantum computational power are those that rely on contextuality.

"Ultimately this should be a tool for experimentalists, to set the bar for what they have to achieve if they want to build a quantum computer that is useful, perhaps as a litmus test for a quantum computer's viability," Emerson says.

Although the mathematical proof of the power of contextuality is limited for now to a particular kind of quantum computation, Emerson thinks that future work might show that it's a general feature of all quantum computation.

Emerson says that the result builds on earlier work from a collaboration with CIFAR Senior Fellow Daniel Gottesman (Perimeter Institute), which grew out of contact they had through the CIFAR program.

"The CIFAR quantum information network and CIFAR funding were both instrumental to developing this result, which was a collective effort from several members of my research group," Emerson says.


Show Reference »


Translate this page: Chinese French German Italian Japanese Korean Portuguese Russian Spanish


 
All comments are reviewed before being posted. We cannot accept messages that refer a product, or web site.If you are looking for a response to a question please use our another feedback page.
Related »

Particle 
7/27/10 
More Accurate Than Heisenberg Allows?
By Ludwig-Maximilians-Universität München
A quantum particle is hard to grasp, because one cannot determine all its properties precisely at the same time. Measurements of certain parameter pairs such as position and momentum …
Measurement 
3/3/13 
★ 
Getting Around the Uncertainty Principle
By University of Rochester
Researchers at the University of Rochester and the University of Ottawa have applied a recently developed technique to directly measure for the first time the polarization states of light. …
Quantum 
1/20/14 
★ 
Peeking into Schrodinger's Box
By University of Rochester
Until recently measuring a 27-dimensional quantum state would have been a time-consuming, multistage process using a technique called quantum tomography, which is similar to creating a 3D image from …
Memory 
7/27/10 
More Accurate Than Heisenberg Allows? – Uncertainty in the Presence of a Quantum Memory
By Ludwig-Maximilians-Universitaet Muenchen (LMU)
Quantum cryptography is the safest way to encrypt data. It utilizes the fact that transmitted information can only be measured with a strictly limited degree of precision. Scientists at …
Quantum 
8/28/14 
★ 
New Technique Uses Fraction of Measurements to Efficiently Find Quantum Wave Functions
By University of Rochester
The result of every possible measurement on a quantum system is coded in its wave function, which until recently could be found only by taking many different measurements of …
Quantum 
9/7/12 
★★ 

University of Toronto Scientists Cast Doubt on Renowned Uncertainty Principle
By University of Toronto
Quantum 
9/24/14 
Are Weak Values Quantum? Don't Bet on It
By Perimeter Institute for Theoretical Physics
Over the past 20 years, a strange idea called a "weak value" has taken root in quantum information science. Many of the things you can do with quantum …
Measurement 
5/29/13 
More Precision from Less Predictability: A New Quantum Trade-off
By Griffith University
Researchers at Griffith University's Centre for Quantum Dynamics have demonstrated that, contrary to what the Heisenberg uncertainty relation may suggest, particle properties such as position and momentum can be …
Cat 
5/14/13 

New Principle May Help Explain Why Nature Is Quantum
By Centre for Quantum Technologies at the National University of Singapore
More » 
 
© Newsline Group  |  About  |  Privacy Policy  |  Feedback  |  Mobile  |  Japanese Edition