Quamputing with atoms and photons

What kinda stuff is best at hosting ghostly bits of quantum information? It’s an important question cos we can’t tell what the next generation of quamputers will be like until we know what they gonna be made of.

Photons are one option cos they can store qubits for relatively long periods (unlike ions and electrons which get stripped of their qubits by any stray electric or magnetic field). The trouble with photons is that they don’t interact easily with each other so its hard to process the quantum information they store.

Another option are qubits in the form of neutral atoms which are naturally protected from the ravages of stray fields (cos they are neutral) and can be easily made to interact with each other to carry out information processing. The trouble with neutral atoms is that it’s easy to lose them, like spilt ball bearings.

So the dream option is to process the qubits as neutral atoms and transport them as photons.

This week Ed “57 Varieties” Hinds at Imperial College in London UK and his crew have unveiled a device that might just make that possible. It’s a microcavity connected to photon waveguides carved into a silicon chip. The idea is that a single atom sits in the cavity where physicists do their quantum data processing. They then transfer the qubit to a photon and ship it out through the waveguides. Simple when ya know.

Except, they don’t yet know how. This is just proof of principle hardware. The team has put it through its paces and says it performs with a throaty growl and a kick like a vodka martini. But a quamputer, it ain’t. That’ll come later.

“These results constitute first steps towards building an optical micro-cavity network on a chip for applications in quantum information processing,” says 57 Varieties in the paper.

The really excitin’ thing is that the device is scalable. It’s small and, in theory at least, easy to connect to other cavities on the same chip using the waveguides. So it should be straightforward to build two or more cavities onto a chip, link ’em together with optical waveguides and start a-computin’ and a-calculatin’.

And if 57 Varieties and his gang do that, we might see some half-decent quamputing at Imperial in the next few years.

Ref: arxiv.org/abs/0710.2116: Atom Detection and Photon Production in a Scalable, Open, Optical Microcavity

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