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Energy cost of a quantum operation

This experiment was carried out thanks to the collaboration of University of Florence, Roma Tre University and Queen’s University of Belfast

One of the obstacles to be overcome in order to make quantum computers commercial products is to solve the problem of quantifying how much energy is needed to perform each operation.

The group of researchers coordinated by Filippo Caruso, of the University of Florence (Unifi), and Marco Barbieri, of the Roma Tre University, has investigated such problem from a thermodynamical perspective, opening the way to the quantification of the energy cost that lies behind process of a single quantum operation, which is an essential step to improve the performance of any machine designed for quantum computing. The study was published in the journal npj Quantum Information edited by Nature.

The team of Florentine physicists – in collaboration with the researchers of Queen’s University in Belfast coordinated by Mauro Paternostro – has developed a theoretical framework based on the verification of the so-called “Landauer principle”, which is one of the fundamental principles of information theory setting the minimum amount of entropy – that is, disorder – and energy dispersed in order to perform a certain logical operation.

“The minimum level of energy consumption described by the American physicist in 1961 is millions of times lower than the cost of modern computers. It is crucial to approach this limit but, to do so, it is necessary to reach very low temperatures and nanoscopic dimensions – says Caruso, Associate Professor of Physics of Matter at Unifi – where the rules of quantum physics come into play, thus experimentally verifying, in the microscopic world, the Landauer principle."

After developing the theoretical scheme, the experimental group of the Roma Tre University has tested it in terms of quantum operations of two-photon states (a photon is a light particle). Barbieri, Professor of Physics of Matter at Roma Tre, explains: “By manipulating two photons, i.e. processing the encoded information, we have measured the consumption of this operation in terms of energy and entropy, thus proposing a new approach to characterize the performance of quantum computers. Our results are the beginning of a promising line of research and we will extend the new method on increasingly larger systems until we reach the size of quantum computers with hundreds and then thousands of logic gates."

 

Publication
date
13 January 2021
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