This Is the Most Complex Integrated Quantum Circuit Ever Made

It might look understated, but you're looking at the most functionally complex integrated quantum circuit ever made from a single material—and it can both generate photons and entangle them, all at the same time.

Put together by a team of researchers from the UK, Japan and the Netherlands, the circuit boasts two photon sources on a silicon chip, which interfere quantum mechanically. For the uninitiated, that interference between multiple photons is what researchers rely on to use quantum mechanics as a tool for information processing.

Usually, though, it's been tough to measure that kind of interference, because it requires the photons—those particles of light—be identical in the first place, which is actually pretty tricky. But Mark Thompson of the University of Bristol, UK, has cracked that problem. He explained to Physics World:

"These sources produce entangled light – which we can control – and quantum mechanically interfere on the same chip. We injected the beam into two regions on the chip (these regions subsequently become the two sources) and combined the quantum light produced using a beam-splitting element, also on the chip. We precisely controlled the path length travelled by the photons through one of the sources by changing the temperature of one of the two waveguides contained in the chip and observed quantum interference fringes."

And those fringes represent the quantum interference between the two photons. Boom, problem solved—and all it took was some of the most complex circuitry known to man. Essentially, they've created the first proper quantum system-on-a-chip, and they claim it could help change the way bulk and fibre optics work in the future. You just might be in for a bit of a wait until it helps speed up your broadband. [Nature Photonics via Physics World]