Scientists have measured a mechanical quantum system without destroying it

(ORDO NEWS) — There is a key aspect of quantum computing that you may not have thought about before. Called “non-destructive quantum measurements”, they refer to the observation of certain quantum states without destroying them in the process.

If we want to create a functioning quantum computer, then obviously it would be useful that it does not break down every second while the calculations are being made. Now scientists have described a new technique for registering quantum measurements without destruction, which promises great promise.

In this case, the study involved mechanical quantum systems – objects that are relatively large in terms of quantum computing, but extremely small for us. They use mechanical motion (such as vibration) to perform the necessary quantum magic, and they can be combined with other quantum systems.

“Our results open up possibilities for performing even more complex quantum algorithms using mechanical systems, such as quantum error correction and multimode operations,” the researchers write in the published paper.

For the purposes of this study, the team assembled a thin strip of high quality sapphire just under half a millimeter thick.

A thin piezoelectric transducer has been used to excite acoustic waves that move units of energy, such as photons, that could theoretically flow through quantum computing processes. Technically, this device is known as an acoustic resonator.

This was the first part of the installation. To make the measurements, the acoustic resonator was connected to a superconducting qubit, the basic building blocks of a quantum computer that can simultaneously store the values ​​1 and 0, and from which companies like Google and IBM have already built rudimentary quantum computers.

By making the state of the superconducting qubit dependent on the number of photons in the acoustic resonator, scientists were able to count this number of photons without actually interacting with them and without transferring any energy.

According to them, it’s like playing a theremin, a strange musical instrument that doesn’t need to be touched to make a sound.

Creating a quantum computational equivalent was not an easy task: Quantum states are usually very short-lived, and part of the innovation in this technique was how these states were stretched out over a longer time.

The team achieved this in part due to the choice of materials, and in part due to the superconducting aluminum cavity providing electromagnetic shielding.

In the course of further experiments, they managed to obtain the so-called “parity measure” of a mechanical quantum system.

The measure of parity is crucial for various quantum technologies, especially when it comes to correcting errors in systems – and no computer can work properly if it regularly makes mistakes.

“Through the interaction of mechanical resonators with superconducting circuits, loop quantum acoustic dynamics can make available various important tools for manipulating and measuring moving quantum states,” the researchers wrote.

All this is very high level in terms of quantum physics, but the bottom line is that this is an important step forward in one of the technologies that could eventually become the basis for future quantum computers, especially in terms of connecting different types of systems together.”

A “kbit-resonator” hybrid device like the one described in this study potentially offers the best of two distinct areas of research: the computational capabilities of superconducting qubits and the stability of mechanical systems. Now scientists have shown that information from such a device can be extracted in a non-destructive way.

There is still a lot of work to be done – once the problem of measuring states is refined and solved, these states will need to be used and manipulated to be of real use – but the huge potential of quantum computing systems may have just come one step closer.

“Here we demonstrate direct measurements of the distribution of the number of phonons and the parity of non-classical mechanical states,” the researchers write.

“These measurements are one of the main building blocks for creating acoustic quantum storage devices and processors.”


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