Feeds

New photonic router works by flipping reflective atom's lid

Look ma! No electronics!

Remote control for virtualized desktops

Quantum boffins from Israel's Weizmann Institute have demonstrated a two-input/two-output router that works entirely with single photons – no electronics required.

It's not the first time a photonic router has been demonstrated, but what's different about the Israeli work is that everything is photonic: the device has two optical inputs, two optical outputs, and can route single photons from either input to either output based solely on a control provided by another single photon.

There are two important differences between this and the current “state of the art”.

On the one hand, there's a big body of work in designing systems that use electrical controls to route photons. The Register has discussed such kit in the past, and noted that it demands a lot of work integrating electro and optical components on the same chip.

On the other, while all-optical switches exist (Australia's CUDOS has been recognised for such work), they operate at the beam level rather than on individual photons.

The latest work, published in Science (abstract here, pre-press here), sets about to resolve a conundrum in quantum information processing: because photons don't normally interact with each other, they're ideal for communications; but because photons don't normally interact, it's hard to create all-photonic gates (by way of counter-example: electrons interact strongly, so it's easy to use an electrical signal to control a gate, but their interaction makes electrons interfere with each others' communications).

What the Weizmann Institute of Science group settled on as their solution was to use single photons to change the state of a single Rubidium atom at the centre of a matrix of four optical fibres (two in, two out). The atom is flipped by a photon, between acting as a mirror or being (effectively) transparent.

Photonic router schematic

The atom in the middle is the key. Image: Dayan et al

For example, if the “control atom” is presenting its reflective state to input 1, a photon arriving at that input will appear at output 1. In that state, the atom will transmit a photon from input 2 to output 1. When the atom's state is flipped, both inputs will appear at output 2, either by transmission (input 1) or reflection (input 2)*.

The researchers say that the state-flip can be accomplished with a single photon (although losses and nonlinearities mean that in practise, as many as three photons might be required).

The key technologies enabling this demonstration are laser cooling (which helps the trapping of the single Rubidium atom), and the high-quality chip-based optical resonators that couple directly to the optical fibres.

“The device we constructed demonstrates a simple and robust system, which should be applicable to any future architecture of such computers. In the current demonstration a single atom functions as a transistor – or a two-way switch – for photons, but in our future experiments, we hope to expand the kinds of devices that work solely on photons, for example new kinds of quantum memory or logic gates”, says Dr Barak Dayan, head of the Weizmann Institute’s Quantum Optics group. ®

*Bootnote – TL;dr version: What's going on at the quantum level is, of course, a little more complex than “reflect or transmit”. What happens is that the control atom absorbs an incoming photon: in the “reflective” state, it re-emits that photon back towards the input fibre, while in its “transmission” state, it emits a photon towards the output fibre.

“The atom radiates in both directions, and the destructive interference with the incoming [light] probe in the forward direction leads to reflection of the probe backwards”, the paper states. ®

Internet Security Threat Report 2014

More from The Register

next story
Antarctic ice THICKER than first feared – penguin-bot boffins
Robo-sub scans freezing waters, rocks warming models
I'll be back (and forward): Hollywood's time travel tribulations
Quick, call the Time Cops to sort out this paradox!
Your PHONE is slowly KILLING YOU
Doctors find new Digitillnesses - 'text neck' and 'telepressure'
Reuse the Force, Luke: SpaceX's Elon Musk reveals X-WING designs
And a floating carrier for recyclable rockets
NASA launches new climate model at SC14
75 days of supercomputing later ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
Bond villains lament as Wicked Lasers withdraw death ray
Want to arm that shark? Better get in there quick
prev story

Whitepapers

Go beyond APM with real-time IT operations analytics
How IT operations teams can harness the wealth of wire data already flowing through their environment for real-time operational intelligence.
The total economic impact of Druva inSync
Examining the ROI enterprises may realize by implementing inSync, as they look to improve backup and recovery of endpoint data in a cost-effective manner.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Mitigating web security risk with SSL certificates
Web-based systems are essential tools for running business processes and delivering services to customers.