Single-photon error corrected communication

Purpose and goal:

We have shown how to transmit information with single photons instead of using light pulses from a laser. We were able to measure that the message we sent had less than one photon per physical symbol upon arrival at the recipient. Many photons were absorbed in the fiber or lost due to imperfect components, but despite this we were able to reproduce the entire message thanks to error correcting codes.

We solved the main technical challenges, to generate single photons with so-called "quantum dots", transmit them over the 22 km quantum channel, and compare 3 different error correcting codes. Expected results and effects:

Since we have shown that light pulses can be miniaturized using single photon technology and error correction, we expect to see more use cases where this can come into play. Such applications can, for example, involve communication in data centers or between satellites where energy use is limited. The marketing department gave the project some positive comments and we hope to license or commercialize the technology in the future.

Approach and implementation:

The experiment involved two laboratories, the photons were sent from the Royal Technical the university college (KTH), Albanova and received at Ericsson´s lab in Kista - after passing through a commercial, but unused, fiber from Stokab. At Albanova, the photons were generated using a so-called quantum dot, and in time slots the polarization of the photons was modulated according to a new protocol for error correction for a photon loss channel.

In Kista, the photons were detected and the message was recreated despite losses in the channel, thanks to the error-correcting code.