The research results were published in the scientific journal Optics Express.

When asked, "How much information can be transmitted using only one photon?" most scientists would answer "a little" (a '1' or a '0'). In theory, however, there is no limit to the amount of information that can be transmitted with a single photon. There are, however, many practical considerations that limit the amount of information per photon. Using an innovative method, researchers at the University of Twente have managed to transmit no less than 10.5 bits of information with a single particle of light.

Method:
Professor Pepijn Pinkse, one of the researchers involved, explains how the system works. “It can be compared to the brightness of a laser pointer on letters mounted on a plate. The illuminated letter is the information contained in the laser pointer's light. The number of letters on the plate determines the amount of information you can transmit with the light.” The main difference is that Professor Pinkse and his team created an alphabet of 9,072 characters, and they, unlike the laser pointer, transmitted the information with a single photon. That was the key challenge in this study: single-photon detection. This is because noise (random photons) can prevent measurement. The researchers devised a clever trick to eliminate any noise. They exploited the fact that individual blue photons can be split into exactly two red photons. The researchers arranged the first photon to send a signal to the detector (which is comparable to a digital camera), which was then opened very briefly. Using a mirror, the second photon was directed to the desired letter of the specially created alphabet. However, they forced this photon to make a slight detour so that it reached the target letter at the exact moment the detector opened. That was the only moment the photons could pass into the detector. In this way, the researchers were able to eliminate the noise.

In practical terms, it's difficult to specify the maximum amount of information that can be transmitted with a single photon, according to Pinkse. "Using our method, there's no theoretical limit to the amount of information that can be sent. The amount of information depends on the size of the alphabet you create. But even if you could create an alphabet with as many characters as there are atoms in our entire universe, you could only transmit a maximum of 270 bits with one photon.".