Integrating electronic and photonic chips breaks record in quantum light detection

University of Bristol’s QET Lab and Université Côte d‘Azur develop device enabling higher performance quantum computers.

Researchers at the University of Bristol, UK, and from Université Côte d‘Azur, France, have developed a tiny device, which, they say, paves the way for higher performance quantum computers and quantum communications: they are significantly faster than the current state-of-the-art, they say.

The researchers, working at Bristol’s Quantum Engineering Technology Labs (QET Labs) and UCd’A have developed a new miniaturized light detector that measures quantum features of light in more detail than was previously possible. The device, made from two silicon chips working together, is used to measure the special properties of so-called “squeezed” quantum light at record high speeds.

Harnessing the properties of quantum physics promises novel routes to outperform the current state-of-the-art in computing, communication and measurement,say the team. The foundation to this development is silicon photonics.

Squeezed light is a quantum effect that is very useful. It can be used in quantum communications and quantum computers and has already been used by the LIGO and Virgo gravitational wave observatories to improve their sensitivity, helping to detect exotic astronomical events such as black hole mergers. So, improving the ways we can measure it can have a big impact,” commetend QET scientists Joel Tasker.

Tasker is co-lead author on a recent paper in Nature Photonics, which describes the latest develpments.

Breaking previous limits

Measuring squeezed light requires detectors that are engineered for ultra-low electronic noise, in order to detect the weak quantum features of light. But such detectors have so far been limited in the speed of signals that can be measured to about 1 GHz.

This has a direct impact on the processing speed of emerging information technologies such as optical computers and communications with very low levels of light. The higher the bandwidth of your detector, the faster you can perform calculations and transmit information,” said co-lead author Jonathan Frazer.

The integrated detector has so far been clocked at an order of magnitude faster than the previous state of the art, and the team is working on refining the technology to go even faster.

The detector’s footprint is less than a square millimeter. This small size enables the detector’s high-speed performance. The detector is built out of silicon microelectronics and a silicon photonics chip.

Much of the focus has been on the quantum part, but now we’ve begun integrating the interface between quantum photonics and electrical readout. This is needed for the whole quantum architecture to work efficiently. For homodyne detection, the chip-scale approach results in a device with a tiny footprint for mass-manufacture, and importantly it provides a boost in performance,” said Professor Jonathan Matthews, who directed the project.

The Quantum Engineering Technology Labs (QET Labs) at the University of Bristol was launched in April 2015 and encompasses activity of over 100 academics, staff and students. It brings together the broader quantum and related activity at Bristol to maximise opportunities for new science discoveries that underpin engineering and technology development. This research was supported by an European Research Council Starting Grant and the Engineering and Physical Sciences Research Council.