Jason Petta, Princeton University
Hard Science

New Condensed Matter State Paves the Way for Scalable Quantum Computers

Illuminating the world of physics one light-matter 'coupling' at a time.

Jasmine SolanaAugust 25th 2016

QUANTUM COUPLING

For particle physicists, studying the interactions between photons and electrons has long been an area of interest. After all, observing such phenomena could eventually lead us to the creation of a viable quantum computer.

Physicist Junichiro Kono and his colleagues at Rice University are making headway on a method to create a new condensed matter state, where electrons in a material “couple” after they are manipulated with light and a magnetic field.

For their work, which was described in Nature Physics, the team made use of a custom-built, finely-tuned cavity for terahertz radiation. The result? The researchers detected one of the strongest light-matter coupling phenomena ever observed.

DRESSING ELECTRONS WITH LIGHT

1-lightandmatt
Xinwei Li. Credit: Jeff Fitlow/Rice University

The condensed matter state that the researchers worked on is similar to what’s known as Bose-Einstein condensates. Named after physicists Satyendra Nath Bose and Albert Einstein, a Bose-Einstein condensate is essentially a state of matter of a dilute gas of bosons cooled to close to absolute zero.

A previous work was able to prompt atoms to form a gas at ultra-cold temperatures at which all atoms lose their individual identities and behave as a single unit. This time, Kono’s team wanted the electrons to be strongly coupled, or “dressed,” with light.

The team designed and constructed a high-quality cavity containing an ultra-thin layer of gallium arsenide—the same one that’s used to study superfluorescence. Then, the physicists tuned the material with a magnetic field to resonate with a certain state of light inside the cavity, resulting in the formation of polaritons.

“This is a nonlinear optical study of a two-dimensional electronic material,” said Qi Zhang, a former graduate student in Kono’s group and lead author of the paper. “When you use light to probe a material’s electronic structure, you’re usually looking for light absorption or reflection or scattering to see what’s happening in the material. That light is just a weak probe and the process is called linear optics.”

The team’s work could pave the way for the advancement of applications that involve quantum information like quantum computers.

“The light-matter interface is important because that’s where so-called light-matter entanglement occurs. That way, the quantum information of matter can be transferred to light and light can be sent somewhere,” Kono said.

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