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Circuit-based quantum computers limited

by on04 December 2023

If they only had more time

Timekeeping quality in circuit-based quantum computations are limited by the achievable circuit complexity, according to a new analysis published in the journal Physical Review Letters.

Vienna University of Technology boffins penned a paper exploring "the effect of imperfect timekeeping on controlled quantum dynamics.”

The boffins proved that since no clock has an infinite amount of energy available (or generates an infinite amount of entropy), it can never simultaneously have perfect resolution and perfect precision. This sets fundamental limits to the possibilities of quantum computers."

The ability to grow systems based on quantum operations from prototypes into practical number-crunching behemoths will depend on how well we can reliably dissect the days into ever finer portions. This is a feat the researchers say will become trickier.

Senior author Marcus Huber, a systems engineer who leads a research group in the intersection of Quantum Information and Quantum Thermodynamics at the Vienna University of Technology said the problem was down to entropy.

Huber and his team lay out the logic that connects entropy as a thermodynamic phenomenon with resolution, demonstrating that without infinite energy at your fingertips, your fast-ticking clock will eventually run into precision problems.

The study's first author, theoretical physicist Florian Meier said: "That means: Either the clock works quickly, or it works precisely — both are not possible at the same time."

Quantum computing, which relies on the temperamental nature of particles hovering on the edge of existence, time is everything. This is not an issue because the particles used in current quantum computers are small. As they increase in number, the risk any one of them could be knocked out of their quantum critical state rises, leaving less time to complete the necessary computations.

This appears to be the first time researchers have looked at the physics of timekeeping as a potential obstacle.

"Currently, the accuracy of quantum computers is still limited by other factors, for example, the precision of the components used or electromagnetic fields," says Huber. "But our calculations also show that today we are not far from the regime where the fundamental limits of time measurement play the decisive role."

Last modified on 04 December 2023
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