Time crystals could unlock a radical new future for quantum computers: ScienceAlert

The path to quantum supremacy is complicated by a fairytale challenge – how do you keep a cloud from changing its shape?

The possible solution sounds almost as fantastic as the problem. You can direct the cloud to dance as it travels, to the beat of a unique material known as a time crystal.

Krzysztof Giergiel and Krzysztof Sacha of the Jagiellonian University in Poland and Peter Hannaford of the Swinburne University of Technology in Australia propose a new type of ‘timing’ circuit that could be tasked with preserving the fuzzy states of qubits as they are carried through logic storms. quantum.

Unlike descriptions of objects that have clearly defined locations and motions, a quantum perspective of the same particle describes characteristics such as its position, momentum, and spin as a blur of probabilities.

This ‘cloud’ of possibilities is best understood in isolation. As the particle interacts with its environment, its probability distribution changes like the probability of a sprinter winning the 100-meter dash at the Olympics, until finally only one result is observed.

Just as a classical computer can use the binary states of particles as ‘on-off’ switches in logic gates, quantum computers can theoretically exploit the propagation of uncertainties in a particle to rapidly solve their own types of algorithms, many of which would be impractical. or even impossible to solve in the old way.

The challenge lies in maintaining the coherence of that quantum cloud of possibility – referred to as a qubit – for as long as possible. With every bump, every electromagnetic breeze, comes an increased risk of errors disrupting the number-crunching process.

Practical quantum computers require hundreds, if not thousands, of qubits to remain intact for long periods, making a full-scale system a monumental challenge.

Researchers have looked at a variety of ways to make the quantum computer more robust, from enclosing individual qubits to protect them from decoherence to building safety nets around them.

Now physicists Giergiel, Sacha and Hannaford have described a new approach that turns quantum computers into a qubit symphony led by the baton of a very strange kind of conductor.

Time crystals are materials that transform into repeating patterns over time. Theorized as curiosities just over a decade ago, versions of these ‘ticking’ systems have since been developed using the gentle nudge of a laser and clusters of ultra-cold atoms, where bursts of light send particles into periodic oscillations that defy time. of the laser.

In a paper available on the arXiv preview server, the trio of physicists propose using the unique periodicity of a time crystal as the basis for a new type of “time-tronics” circuit. Used to direct the subtle waves of a large number of information-laden qubits, this periodicity can help reduce the accidental collisions that are responsible for many errors.

Such a temporal circuit of constantly moving qubits would make it easier to steer almost any computer particle into the path of another, entangling their quantum possibilities in useful rather than error-prone ways.

While the proposal remains purely theoretical, the team showed how the physics of clusters of potassium ions cooled to near-absolute temperatures and driven by a laser pulse could provide an “orchestra” for the qubits to waltz.

Translating the idea into a practical, full-scale quantum computer would require years of innovation and experimentation, if it works at all.

However, now that we know that at least some types of time crystals exist and can be used for practical purposes, the challenge of holding a cloud may not be such a fabulous quest after all.

This study is available on the arXiv preview server.

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