9GHz squeezed light detector boosts quantum photonics

9GHz squeezed light detector boosts quantum photonics

Technology News |
By Nick Flaherty

Researchers in the UK and France have developed a 9GHz detector for ‘squeezed light’ that can boost the performance of photonic quantum computers and quantum communications.

Researchers from the University of Bristol’s Quantum Engineering Technology Labs (QET Labs) and Université Côte d’Azur developed the silicon photonics detector that can handle reduced quantum uncertainty, or squeezed light, at high speed. This is a key step to fully integrated quantum phtonics chips, they say.

“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,” said Joel Tasker, co-lead author of a paper in Nature and a researcher at Bristol.

Current detectors operate up to 1GHz.

“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.

At 0.82mm2, the detector footprint is less than a square millimetre and is built with CMOS silicon and germanium-on-silicon nanophotonics with silicon-germanium (SiGe) integrated amplification electronics. By reducing the capacitance of the chip, the detector has a 3 dB bandwidth of 1.7 GHz and is shot-noise limited to 9 GHz.

The detector can measure the continuous spectrum of squeezing from 100 MHz to 9 GHz of a broadband squeezed light source pumped with a continuous-wave laser, and the team used the detector to perform state tomography to re-build quantum states. This provides fast, multipurpose, homodyne detectors for continuous-variable quantum optics, and opens the way to full-stack integration of photonic quantum devices say the researchers.

“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.

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