In a potential boost for quantum computing and communi­cation, a European research colla­boration reported a new method of controlling and mani­pulating single photons without generating heat. The solution makes it possible to integrate optical switches and single-photon detectors in a single chip. The team reported to have developed an optical switch that is recon­figured with micro­scopic mechanical movement rather than heat, making the switch compatible with heat-sensitive single-photon detectors.

Optical switches in use today work by locally heating light guides inside a semi­conductor chip. “This approach does not work for quantum optics,” says Samuel Gyger, a PhD student at KTH Royal Institute of Techno­logy in Stockholm. “Because we want to detect every single photon, we use quantum detectors that work by measuring the heat a single photon generates when absorbed by a super­conducting material,” Gyger says. “If we use traditional switches, our detectors will be flooded by heat, and thus not work at all.”

The new method enables control of single photons without the disad­vantage of heating up a semiconductor chip and thereby rendering single-photon detectors useless, says Carlos Errando Herranz, who conceived the research idea and led the work at KTH as part of the European Quantum Flagship project, S2QUIP. Using microelectro­mechanical (MEMS) actuation, the solution enables optical switching and photon detection on a single semi­conductor chip while maintaining the cold tempera­tures required by single-photon detectors. “Our techno­logy will help to connect all building blocks required for inte­grated optical circuits for quantum techno­logies,” Errando Herranz says.

“Quantum techno­logies will enable secure message encryp­tion and methods of computation that solve problems today's computers cannot,” he says. “And they will provide simulation tools that enable us to understand funda­mental laws of nature, which can lead to new materials and medicines.” The group will further develop the technology to make it compatible with typical elec­tronics, which will involve reducing the voltages used in the experi­mental setup.

Errando Herranz says that the group aims to integrate the fabri­cation process in semi­conductor foundries that already fabricate on-chip optics – a necessary step in order to make quantum optic circuits large enough to fulfill some of the promises of quantum techno­logies. (Source: KTH)

Reference: S. Gyger et al.: Reconfigurable photonics with on-chip single-photon detectors, Nat. Commun. 12, 1408 (2021); DOI: 10.1038/s41467-021-21624-3

Link: Quantum Nano Photonics, Dept. of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden