Researchers invent ‘quantum flute’ that can make light particles move together

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 Review Letters and Nature Physics, the breakthrough could lead the way towards realizing quantum memories or new forms of error correction in quantum computers, and observing quantum phenomena not 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 created by drilling staggered holes – like holes in a flute.

“Like 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, 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 because of this system, they all work together 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 from a single 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 our notes and see the effect of the interaction as it happens. It’s really beautiful to ‘see’ a quantum interaction with your eye, says UChicago postdoctoral researcher Srivatsan Chakram, the paper’s co-first author, now an assistant professor at Rutgers University.

Graduate student Kevin He was the other lead author on the paper. Other co-authors were graduate students Akash Dixit and Andrew Oriani; former UChicago students Ravi K. Naik (now at UC Berkeley) and Nelson Leung (now at Radix Trading); postdoctoral researcher Wen-Long Ma (now affiliated with the Institute of Semiconductors of the Chinese Academy of Sciences); Prof. dr. Liang Jiang of the Pritzker School of Molecular Engineering; and visiting researcher Hyeokshin Kwon of the Samsung Advanced Institute of Technology in South Korea.

Schuster is a member of the James Franck Institute and the Pritzker School of Molecular Engineering. The researchers used the University of Chicago’s Pritzker Nanofabrication Facility to manufacture the devices.

References:

1. Srivatsan Chakram, Kevin He, Akash V. Dixit, Andrew E. Oriani, Ravi K. Naik, Nelson Leung, Hyeokshin Kwon, Wen-Long Ma, Liang Jiang, David I. Schuster. Multimode photon blockage. Natural Physics, 2022; DOI: 10.1038/s41567-022-01630-y
2. Srivatsan Chakram, Andrew E. Oriani, Ravi K. Naik, Akash V. Dixit, Kevin He, Ankur Agrawal, Hyeokshin Kwon, David I. Schuster. Seamless High-Q Microwave Cavities for Multimode Circuit Quantum Electrodynamics. Physical Assessment Letters, 2021; 127 (10) DOI: 10.1103/PhysRevLett.127.107701