In a recent issue of Physical Review Letters, a team of researchers including IQC postdoctoral fellow Marco Piani explored a unified framework for all correlations that respect the so-called no-signalling principle.
In the article, the researchers conclude that such a unified framework is useful to compare different kinds of correlations: "classical, quantum, and stronger-than-quantum" and to understand why stronger-than-quantum correlations do not seem to appear in nature.
The article was the result of research conducted by Piani and several co-investigators working in Barcelona, Spain, and Gdask, Poland. Quantum correlations are known to be stronger-than-classical. This is due to the property known as entanglement, often considered the fundamental trait that distinguishes quantum mechanics from classical mechanics. Though stronger-than-classical, quantum correlations still obey the principle of "no signalling," which means they cannot lead to instantaneous communication between distant parties.
In this sense, one can say that quantum mechanics is compatible with Einstein's theory of relativity. This leads to the question of whether the compatibility with special relativity forces correlations to be at most as strong as quantum ones. It turns out this is not the case. At least at a hypothetical level there are correlations that are stronger-than-quantum and still no-signalling. Many researchers have therefore focused their efforts on understanding why quantum correlations are as strong as they are, trying to find, for example, some physical principle which would single out quantum correlations among the no-signalling ones.
Piani and his co-authors prove that even asking for the validity of quantum mechanics at a local level, together with no-signalling at the level of correlations, is still not enough to single out quantum correlations as soon as more than two parties are considered.
Founded in 2002, the mission of the Institute for Quantum Computing (IQC) is to aggressively explore and advance the application of quantum mechanical systems to a vast array of relevant information processing techniques.
A part of the University of Waterloo, Waterloo, Ont., Canada, IQC creates a truly unique environment fostering cutting-edge research and collaboration between researchers in the areas of computer, engineering, mathematical and physical sciences.
At the time of this release, IQC has 17 faculty members, 22 postdoctoral fellows and over 55 students and research assistants, as well as a support staff of 18.
The Institute for Quantum Computing acknowledges the support of the Government of Canada through Industry Canada and the Government of Ontario through the Ministry of Research and Innovation.