Physicists at the University of Chicago have invented a “quantum flute” that, like the Pied Piper, can force light particles to move together in a way never seen before.

Described in two studies published in Physical Assessment Letters and Nature physicsthe breakthrough could point the way to the realization of quantum memories or new forms of error correction in quantum computers, and the observation of quantum phenomena that cannot be seen in nature.

Associate Prof. David Schuster’s lab is working on quantum bits — the quantum equivalent of a computer bit — that exploit the strange properties of particles at the atomic and subatomic level to do things that would otherwise be impossible. In this experiment, they worked with light particles, known as photons, in the microwave spectrum.

The system they devised consists of a long cavity made in a single block of metal, designed to receive photons at microwave frequencies. The cavity is made by drilling staggered holes, like holes in a flute.

“Just like in the musical instrument,” Schuster said, “you can send one or more wavelengths of photons through the whole thing, and each wavelength creates a ‘note’ that can be used to encode quantum information.” The researchers can then control the interactions of the “notes” using a master quantum bit, a superconducting electrical circuit.

But their strangest discovery was the way the photons behaved together.

In nature, photons almost never interact – they just pass through each other. With careful preparation, scientists can sometimes trigger two photons to react to each other’s presence.

“Here we’re doing something even weirder,” Schuster said. “At first, the photons don’t interact at all, but when the total energy in the system hits a tipping point, all of a sudden they’re all talking to each other.”

It’s extremely odd to have so many photons “talking” to each other in a lab experiment, akin to seeing a cat walk on hind legs.

“Normally, most particle interactions are one-to-one — two particles that bounce or attract each other,” Schuster said. “If you add a third, they usually still interact sequentially with one or the other. But this system lets them all interact at the same time.”

Their experiments tested only five “notes” at a time, but the scientists could eventually envision running hundreds or thousands of notes through a single qubit to check them. With an operation as complex as a quantum computer, engineers want to simplify everywhere they can, Schuster said, “If you could build a 1,000-bit quantum computer and you could control them all via one bit, that would be incredibly valuable. “

The researchers are also enthusiastic about the behavior itself. No one has observed anything like these interactions in nature, so the researchers also hope the discovery could be useful for simulating complex physical phenomena not even seen here on Earth, including perhaps even some of the physics of black holes.

Other than that, the experiments are just plain fun.

“Normally, quantum interactions take place over length and time scales that are too small or too fast to see. In our system, we can measure individual photons in all of our notes and see the effect of the interaction as it happens. It’s really neat.” to ‘see’ a quantum interaction with your eye,’ said UChicago postdoctoral researcher Srivatsan Chakram, the paper’s co-first author, now an assistant professor at Rutgers University.

Source and credits: https://phys.org/news/2022-07-scientists-quantum-flute-particles