Scientists connect quantum bits to sound over record distances

Scientists at the Institute for Molecular Engineering at the University of Chicago have made two major advances in the development of quantum technology. In one study, they entangled two quantum bits using sound for the first time; in another case, they built the long-term link of the highest quality between two qubits to date. This work brings us closer to quantum technology to create more powerful computers, ultra-sensitive sensors and secure transmissions.

"These are two transformative advances in quantum communications," said co-author Andrew Cleland, professor John A. MacLean Sr. of Molecular Engineering at EMI and Argonne National Laboratory, affiliated with UChicago. A leader in the development of superconducting quantum technology, he led the team that built the first "quantum machine", demonstrating quantum performance in a mechanical resonator. "One of these experiments shows the accuracy and accuracy that we can now achieve, and the other demonstrates a new fundamental capability for these qubits."

Scientists and engineers see a huge potential in quantum technology, a field that uses the strange properties of nature's smallest particles to manipulate and transmit information. For example, under certain conditions, two particles can be "entangled" – their fate is tied even when they are not physically connected. The entanglement of particles allows you to do all kinds of interesting things, such as instantaneous transmission of information in the space or the creation of unalterable networks.

But technology still has a long way to go – literally: an enormous challenge is to send quantum information over a considerable distance, along cables or fibers.

In a study published on April 22 in Physical NatureCleland's lab has been able to build a system based on superconducting qubits that exchange quantum information along a track of nearly a meter long with extreme fidelity – with well-performing performance higher.

"The coupling was so strong that we can demonstrate a quantum phenomenon called" quantum ping-pong ": send and then capture individual photons as they bounce," said Youpeng Zhong, graduate student of Cleland's group and first author of the article. .

One of the scientific breakthroughs was building the right device to send the signal. The key formed the pulses correctly – in the form of an arc, as if you were opening and closing a valve slowly, at the proper speed. This method of "limiting" quantum information helped them to obtain such clarity that the system could successfully pass a quantum entanglement reference measurement, called Bell's test. This is a first for superconducting qubits and could be useful for the construction of quantum computers as well as for quantum communications.

The other study, published on April 26 in Science, shows a way to entangle two superconducting qubits using sound.

Scientists and engineers who engage in quantum technology face the challenge of being able to convert quantum signals from one medium to another. For example, microwave light is perfect for carrying quantum signals around internal chips. "But you can not send quantum information by air in microwaves, the signal is simply overwhelmed," Cleland said.

The team has developed a system that can translate the microwave language of the qubits into acoustic sound and pass it on the chip, using a receiver at the other end, which could perform the reverse translation.

It took a bit of creative engineering: "Microwaves and acoustics are not friends, so we had to separate them into two different materials and stack them one on the back. 39; other, "said Audrey Bienfait, postdoctoral researcher and first author of the study. "But now that we've shown it's possible, it opens up exciting new possibilities for quantum sensors."