Detecting a single photon may seem overkill for most purposes. However, looking at such tiny amounts of light is essential for researchers working with quantum computers as well as for chip manufacturers, just to mention two examples. Sander Dorenbos and Val Zwiller, two scientists from the University of Delft, have developed a way to double the efficiency of currently commercially available single photons detectors. In early 2012, they have founded a company together with Floor van de Pavert (see related article) to commercialize their technology.
Dr. Dorenbos, what is the technology behind your single photon detector?
Our device is based on a superconducting nano-wire. It is basically a 5 nanometers-thick wire that becomes a superconductor if it is cooled at extremely low temperatures, below -270 °C. A single photon hitting the superconducting wire is enough to produce a signal that can be sent to an optical fibre and detected. The wire itself sits on a small chip and can be manufactured in different shapes, a grid or a spiral, for example.
How did you achieve a better sensitivity?
The original technology for nano-wire detectors was developed by other groups in the US and Russia, but the efficiency was low. We modified the design of such device so that the detection efficiency would be significantly improved. We used different materials as substrate and we added a sort of mirror behind the nano-wire that reflects the photons back, multiplying their impact. The resulting efficiency is twice that of currently available single photon detectors in the infrared spectrum.
Can you make a few examples of applications using single photon detectors?
To date, people working with single photons are mostly scientists. For example, there are lots of studies on quantum computers that use single photons as bits. Chip manufacturers also use single photon detectors to check their products: working chips emit a very tiny light that can be detected with the suitable equipment. And in the future, single photon detectors will be likely used for medical imaging.
What are the next steps of your work?
We are working to increase the efficiency further. We also aim to develop arrays with multiple detector chips that could work like extremely sensitive cameras, opening the way to new applications.