Seeing quantum mechanics with the naked eye

Ashley N. Paddock, ashley.paddock@photonics.com

A new semiconductor chip that converts electrons into a quantum state that emits light, yet is large enough to see with the naked eye, could lay the groundwork for a new generation of ultrasensitive gyroscopes.

Quantum mechanics normally shows its influence over tiny particles only at ultralow temperatures, but the chip’s developers, scientists at the University of Cambridge, mixed electrons with light to synthesize supersize quantum particles that behave like superconductors.

Building microscopic cavities that tightly trap light into the vicinity of electrons within the chip, they produced lightweight particles called polaritons that roam freely.

Injecting the polaritons in two laser spots, the researchers found that the resulting quantum fluid spontaneously oscillated backward and forward. In the process, they formed some of the most characteristic quantum pendulum states known to scientists, but thousands of times larger than normal. Their research appeared in the Jan. 8 issue of Nature Physics.

Courtesy of Meeblax, Flickr.

“These polaritons overwhelmingly prefer to march in step with each other, entangling themselves quantum mechanically,” said researcher Dr. Gab Christmann.

The quantum liquid that resulted had some peculiar properties, including trying to repel itself. In addition, it could swirl around only in fixed amounts, producing vortices laid out in regular lines.

By moving the laser beams apart, Christmann and his colleagues directly controlled the sloshing of the quantum liquid, which formed a pendulum that could beat a million times faster than a human heart.

“This is not something we ever expected to see directly, and it is miraculous how mirror-perfect our samples have to be,” Christmann said. “We can steer our rivers of polariton quantum liquid on the fly by scanning around the laser beams that create them.”

Increasing the number of laser beams created even more complicated quantum states. The goal of the work is to make such quantum states at room temperature and using an electrical battery, which would allow a new generation of ultrasensitive gyroscopes to measure gravity and magnetic field, and to create quantum circuits.

“Just to see and prod quantum mechanics working in front of your eyes is amazing,” Christmann said.