World’s smallest quantum light detector integrated on silicon chip
Researchers say that the integration of the detector, which is smaller than a human hair, is a step towards the age of quantum photonic technologies, and that the use of established, commercial manufacturing methods could enable scalability
Researchers at the University of Bristol have reported that they have integrated the world’s tiniest quantum light detector onto a silicon chip, representing an important breakthrough in scaling quantum technology. The paper has been published in Science Advances.
A critical moment in unlocking the information age was when scientists and engineers were first able to miniaturise transistors onto cheap microchips in the 1960s. Similarly, the authors of the new study say that the integration of this quantum light detector, which is smaller than a human hair, onto a silicon chip is another step towards the age of quantum technologies using light.
Making high-performance electronics and photonics at scale is fundamental to realising the next generation of advanced information technologies. Figuring out how to make quantum technologies in existing commercial facilities is an ongoing international effort being tackled by both academic institutes and companies around the world.
It could prove crucial for quantum computing to be able to make high-performance quantum hardware at scale, since it is anticipated that vast numbers of components will be needed to build even a single machine.
In pursuit of this goal, the scientists say they have demonstrated a type of quantum light detector that is implemented on a chip with a circuit that occupies 80 µm by 220 µm. Critically, they add that the small size means the quantum light detector can be fast, which is key to unlocking high-speed quantum communications and enabling high-speed operation of optical quantum computers.
Compatibility with established and commercially accessible fabrication techniques also improves the prospects for early incorporation into other technologies such as sensing and communications.
“These types of detectors are called homodyne detectors, and they pop up everywhere in applications across quantum optics” explains Jonathan Matthews, a professor at the University of Bristol and director of the Quantum Engineering Technology Labs, who led the research. “They operate at room temperature, and you can use them for quantum communications, in incredibly sensitive sensors – like state-of-the-art gravitational wave detectors – and there are designs of quantum computers that would use these detectors.”
In 2021 the Bristol team showed how linking a photonic chip with a separate electronic chip can increase speed of quantum light detectors. Now, with a single electronic-photonic integrated chip, the team say they have further increased speed by a factor of 10 whilst reducing footprint by a factor of 50.
According to the researchers, as well as being fast and small, the detectors are also sensitive.
“The key to measuring quantum light is sensitivity to quantum noise,” explains co-author Giacomo Ferranti. “Quantum mechanics is responsible for a minute, fundamental level of noise in all optical systems. The behaviour of this noise reveals information about what kind of quantum light is travelling in the system, it can determine how sensitive an optical sensor can be, and it can be used to mathematically reconstruct quantum states. In our study it was important to show that making the detector smaller and faster did not block its sensitivity for measuring quantum states.”
The authors note that there is more exciting research to do in integrating other disruptive quantum technology hardware down to the chip scale. With the new detector, the efficiency needs to improve, and there is work to be done to trial the detector in lots of different applications.
Matthews adds: “We built the detector with a commercially accessible foundry in order to make its applications more accessible. While we are incredibly excited by the implications across a range of quantum technology, it is critical that we as a community continue to tackle the challenge of scalable fabrication of quantum technology. Without demonstrating truly scalable fabrication of quantum hardware, the impact and benefits of quantum technology will be delayed and limited.”
