Bristol University researchers have demonstrated the world’s smallest optical controlled NOT gate–the building block of a quantum computer–fabricated from silica wave-guides on a silicon chip.

The team generated pairs of photons, each encoding a quantum bit or qubit of information. They coupled these photons into and out of the millimeter-sized chip, using optical fibers.

Quantum optical circuits have typically relied on large optical elements, with photons propagating in air. This has made them hard to build and difficult to scale up.

University of Bristol News Release