Photon Switch On Superconducting Chip The Newest in Quantum Computing

With a method to efficiently manipulate light on a superconducting chips, physicists at UC Santa Barbara are adding another module to build the quantum devices of the future, which includes quantum computers.

A team in the lab of John Martinis, UCSB professor of physics, achieved an "unprecedented level" of manipulating light on a superconducting chip, which is a crucial step in the field of superconducting quantum devices,according to first author Yi Yin who worked on the project when she was a postdoctoral fellow in the lab from 2009 to 2012. The researchers published their findings this week in Physical Review Letters.

"In our experiment, we caught and released photons in and from a superconducting cavity by incorporating a superconducting switch," said Yin. "By controlling the switch on and off, we were able to open and close a door between the confined cavity and the road where photons can transmit. The on/off speed should be fast enough with a tuning time much shorter than the photon lifetime of the cavity."

Cavities, for example in nano-diamonds, are the memory units of quantum devices that can hold a single and specific photon, which carries quantum data by being entangled with another far away photon and having a certain polarization. Yin explained that not only can the switch be in an on/off state, it also can be opened continuously, like a shutter. In that way, the research team was able to shape the released photons in different wave forms –– a key element for the next step they want to accomplish: controlled photon transfer between two distant cavities.

This would open up a much more efficient and practicable way to facilitate remote quantum communications, as it is already done in experiments and prototype networks.

"The shutter controls the release of this photon," said Chen, also a postdoctoral fellow in the Martinis lab. "You need to perfectly transfer a bit of information, and this shutter helps you to do that."

He said that, instead of another shutter, Yin used classical electronics to drive the photon. She then captured the signal in the superconducting cavity, in an area called the meander, or the resonator. The shutter was then able to control the release of the photon.

Wenner explained that the resonator, a superconducting cavity, is etched on the flat, superconducting chip –– which is about one quarter of an inch square. It is chilled to a temperature of about minus-273.12 degrees Celsius.