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

The path to quantum supremacy is complicated by an imaginative challenge – how do you hold a cloud without changing its shape?

The potential solution seems just as imaginative as the problem. You can direct the cloud to dance as it travels, to the rhythm of a unique substance known as a time crystal.

Krzysztof Giergiel and Krzysztof Sacha of Jagiellonian University in Poland and Peter Hannaford of Swinburne University of Technology in Australia suggest that a new kind of “time” circuit might be up to the task of preserving the mysterious states of quantum bits while carrying them through the storms of the universe. Quantum Logic

In contrast to descriptions of objects as having clearly defined positions and motions, the quantum view of the same particle describes features such as its position, momentum, and spin as a blur of probabilities.

This “cloud” of possibilities is best understood in isolation. Once a particle interacts with its environment, the probability spread changes like the odds of a runner winning the 100 meter dash at the Olympic Games, until in the end only one outcome is observed.

Just as a classical computer can use the binary states of particles as “on-off” switches in logic gates, quantum computers could theoretically exploit the propagation of particle uncertainty to quickly solve their own kinds of algorithms, many of which would be impractical or even impossible to solve the old-fashioned way.

The challenge is to hold together that quantum cloud of possibilities – referred to as qubits – for as long as possible. With every bump, every electromagnetic breeze, comes an increasing risk of number-crunching errors.

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

Researchers have sought a variety of ways to make quantum computing more powerful, either by locking individual qubits to protect them from losing coherence or building safety nets around them.

Now, physicists Gergel, Sascha, and Hannaford describe a new approach that turns quantum computers into a qubit symphony guided by a very strange type of conductor.

Time crystals are materials that shift in repeating patterns over time. These systems were considered exotic just over a decade ago, and versions of these “timed” systems have since been developed using a gentle burst of lasers and ultracold clusters of atoms, with bursts of light sending the particles into periodic fluctuations that defy laser timing.

On paper Available on the arXiv prereview server, the trio of physicists propose using the unique periodicity of the time crystal as the basis for a new type of “time electronics” circuit. This periodicity is used to direct microwaves to large numbers of information-laden qubits, and can help reduce the accidental collisions responsible for many errors.

Such a time circuit of constantly drifting qubits would make it easy to direct any of the computer's particles onto another path, entangle their quantum capabilities in useful ways rather than error-inducing ones.

While the proposal is still purely theoretical, the team has shown how the physics of clusters of potassium ions cooled to near-absolute temperatures and directed by a laser pulse can provide an “orchestra” of qubits.

Translating the idea into a practical, full-scale quantum computer will require years of innovation and experimentation, if the idea ever succeeds.

However, now that we know at least some types of time crystals exist and can be used for practical purposes, the challenge of carrying a cloud may not be just a fanciful endeavor after all.

This study is available on a pre-peer review server. arksif.