Feeds

Single chip photon source brings quantum comms closer

Turning research labs into devices

Build a business case: developing custom apps

Down at the “basic research” level, there's a lot the labs can accomplish with quantum mechanics: entanglement, information teleportation, simple quantum computations and more. Now, an international collaboration believes it's brought exploitation of quantum effects closer to a commercial development.

The researchers have created what they hope lays out the “yellow brick road” they need to follow to create a single integrated source of single photons – ultimately at high enough output rates to permit quantum communications in the megahertz range.

The international team comprised CUDOS (Centre for Ultra high bandwidth Devices for Optical Systems) researchers from Macquarie University and Sydney University, and the Laboratory of Physics of Condensed Matter at France's Université Nice Sophia Antipolis.

Their work combines a source of single photons, lithium niobate waveguides, low-loss laser inscribed circuits, and fast (>1 MHz) fibre coupled electro-optic switches.

As the Macquarie University release explains, the devices “combined passive glass routers created by femtosecond laser writing, nonlinear waveguides in a highly advanced chip, and fast optical switching elements. The photons were generated in a lithium niobate chip developed in the group of Professor Sébastien Tanzilli and Dr Olivier Alibart at the Université Nice Sophia Antipolis. Femtosecond laser-written glass circuits produced at Macquarie were used to embed the Nice chip into the larger experiment.”

“Many people are trying to build single photon sources,” explained Macquarie University's associate professor Mike Steel, who also serves as science leader for CUDOS's quantum integrated photonics Centre of Excellence.

“The key problem is that most of the time you get nothing, sometimes you get single photons, and other times you get multiple photons.”

In essence, most sources of single photons have an unusable output most of the time. “By introducing the switching process – that was Sydney University's contribution – we reduce the number of zeroes and the number of multiple pairs,” Steel went on.

Building on work last year that demonstrated a reliable source of photon pairs, he said, PhD student Thomas Meany has demonstrated that the system can be scaled up. Meany has, he said, “moved the switching technology from a curiousity into something that's scalable – it turns the stochastic photon source into a deterministic source.”

Illistration of single photon setup

Illustration of the single photon experimental setup. Image: Thomas Meany et al

Meany told The Register that realising a photon source as a component has potential applications both in quantum communications and quantum computing.

A high-quality source of single photons that can be entangled for information teleportation “is a hot application of what this sort of system is projected to be used for,” he said. In computing systems, “we would expect this sort of technology would form a core unit to produce qubits in a quantum computer. A series of these devices would product a series of qubits, which is a key challenge of optical quantum computing.”

Steel added that the device could also form the basis of repeaters in quantum communications systems. “The process of amplification introduces noise,” he said. “In the quantum system, the noise is as big as the single photon, which destroys the information.

“We imagine a product like this as being able to sit in a quantum computer, a quantum relay, every hundred kilometres or so.”

While The Register can't claim any deep understanding of quantum mechanics, the idea of a quantum repeater seems to violate the notion that you can't observe (including amplify) an entangled system without destroying the entanglement.

The problem, Steel said, is that the no-cloning theorem means you can't copy a quantum state without destroying it. The repeater workaround, he explained, is to establish an entangled pair on each of the links in a “repeatered” system.

“By performing a new measurement at each junction, I can extend the entanglement. So a measurement at node 2 will create entanglement between node 1 and node 3, and so on.”

Right now, the output rate of the device is in the tens of Hertz, but Steel says this will improve.

“Photons might be generated at tens of kilohertz or faster, but few of them make it out of the chip – coupling them into the fibre is difficult, and so far, detectors are not especially efficient.

“We can infer that the on-chip rate, which we can't observe directly but can infer, is in the hundreds of kilohertz to megahertz rate. As more of the technology moves on chip, the losses will improve,” he said.

The work is available at Arxiv here, and is to be published in Laser & Photonics Reviews. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
Boffins attempt to prove the UNIVERSE IS JUST A HOLOGRAM
Is this the real life? Is this just fantasy?
Our LOHAN spaceplane ballocket Kickstarter climbs through £8000
Through 25 per cent but more is needed: Get your UNIQUE rewards!
China building SUPERSONIC SUBMARINE that travels in a BUBBLE
Shanghai to San Fran in two hours would be a trick, though
LOHAN tunes into ultra long range radio
And verily, Vultures shall speak status unto distant receivers
SpaceX prototype rocket EXPLODES over Texas. 'Tricky' biz, says Elon Musk
No injuries or near injuries. Flight stayed in designated area
Galileo, Galileo! Galileo, Galileo! Galileo fit to go. Magnifico
I'm just a poor boy, nobody loves me. But at least I can find my way with ESA GPS by 2017
EOS, Lockheed to track space junk from Oz
WA facility gets laser-eyes out of the fog
prev story

Whitepapers

Top 10 endpoint backup mistakes
Avoid the ten endpoint backup mistakes to ensure that your critical corporate data is protected and end user productivity is improved.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Backing up distributed data
Eliminating the redundant use of bandwidth and storage capacity and application consolidation in the modern data center.
The essential guide to IT transformation
ServiceNow discusses three IT transformations that can help CIOs automate IT services to transform IT and the enterprise
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.