Photons On Demand Now Possible With Breakthrough

Researchers have achieved a breakthrough in photonics that will help create extremely compact optical chips that deliver a photon at a time.

Asian Scientist (Oct. 17, 2013) – A breakthrough in photonics that will help create extremely compact optical chips, a hair’s width in size and delivering a photon at a time, has been achieved by researchers in Australia.

“This result has applications in the development of complex quantum technologies, including completely secure communications, quantum measurement, the simulation of biological and chemical systems and of course quantum computing,” said Dr Alex Clark, leader of the research team from the Australian Research Council Centre of Excellence for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS).

Photons are single particles of light that can readily carry quantum information. The importance of being able to develop a chip that can deliver one photon at a time at very high rates is to provide scalability for the extraordinary diversity of quantum technologies that could enhance computing and communication infrastructure.

Scalability refers to the ability to use many photon sources in parallel to carry out complicated tasks.

“It is easy for us to generate photons at high rates, but it’s much harder to ensure they come out one by one because photons are gregarious by nature and love to bunch together,” said lead author Matthew Collins, a PhD student from CUDOS at the University of Sydney.

“For that reason the quantum science community has been waiting over a decade for a compact optical chip that delivers exactly one photon at a time at very high rates.”

In fact, the creation of a single photon in an optical circuit has been possible for some years, but previous demonstrations have been difficult to implement and scale up or have been excessively noisy. This has limited the single photon technology to being either very slow or having a high probability of error.

In their research, published in Nature Communications, the researchers showed how multiple imperfect sources of photons on a single chip can be combined to produce a much higher quality source. The photons here are generated from a pulsed laser.

The breakthrough came when the scientists at CUDOS developed photonic chips that slow light, making single photon generation more likely. The new chips also reduced energy demands and allowed extremely compact devices with lengths no longer than 200 microns, the width of a human hair.

“The smaller these systems are, the more we can fit onto a chip, and the more we can fit onto a chip the more likely we are to guarantee a single photon when we want it,” said co-author Associate Professor Michael Steel.

The next step for the researchers is to integrate all the components of this scheme onto a single chip so that an on-demand ‘push button’ single photon source can be deployed in future photonic quantum technologies.

The article can be found at: Collins et al. (2013) Integrated Spatial Multiplexing Of Heralded Single-Photon Sources.

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Source: University of Sydney; Photo: NASA/Sonoma State University/Aurore Simonnet (Flickr/CC).
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