Quantum computers have attracted considerable interest of late for their potential to crack problems in a few hours where they might take the age of the universe (i.e., tens of billions of years) on the best supercomputers. Their real-life applications are manifold and range from drugs and materials design to solving complex optimisation problems. They are therefore primarily intended for scientific and industrial research.
Traditionally, “quantum supremacy” is sought from the point of view of raw computing power: we want to calculate (much) faster.
However, the question of its energy consumption could also now warrant research, with current supercomputers sometimes consuming as much electricity as a small town (which could in fact limit the increase in their computing power). Information technologies, at their end, accounted for 11% of global electricity consumption in 2020.
Why focus on the energy consumption of quantum computers?
Since a quantum computer can solve problems in a few hours where a supercomputer might take several tens of billions of years, it is natural to expect it will consume much less energy. However, manufacturing such powerful quantum computers will require that we solve many scientific and technological challenges, potentially over one to several decades of research.
A more modest goal would be to create less powerful quantum computers, capable of solving computations in a time relatively comparable to supercomputers, but using much less energy.
Google, Amazon, Microsoft and IBM are some of the tech giants to have taken an interest in quantum computing.
Graham Carlow
This potential energy benefit of quantum computing has already been discussed. Google’s Sycamore quantum processor consumes 26 kilowatts of electrical power, far less than a supercomputer, and runs a test quantum algorithm in seconds. Following the experiment, scientists put forward classical algorithms to simulate the quantum algorithm. The first proposals for classical algorithms required much more energy – which seemed to demonstrate the energy advantage of quantum computing, but they were soon followed by other proposals, which were much more energy efficient.
The question of the energy advantage is therefore still open to question and is an open research topic, especially since the quantum algorithm performed by Sycamore has no identified “useful” application to date.
Superposition: the fragile phenomenon at the heart of quantum computing
To know whether quantum computers can be expected to provide an energy advantage, it is necessary to understand the fundamental laws according to which they operate.
Quantum computers manipulate physical systems called qubits (for quantum bits) to perform a calculation. A qubit can take two values: 0 (the “ground state”, of minimum energy) and 1 (the “excited state”, of maximum energy). It can also…
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Auteur: Marco Fellous-Asiani, Post-doctorant en information quantique au Centre of New Technologies, University of Warsaw
