First quantum communication uses "trits" instead of bits

17 Jun 2002

For the first time, physicists have exploited the laws of quantum mechanics to send data, and with their technique have conveyed information more efficiently than with traditional means. In contrast to a traditional computer, in which messages consist of tiny electric pulses encoded in binary form, researchers at the University of Innsbruck in Austria send messages consisting of single photons which can be coded as 0s, 1s, and 2s, setting up a base three system called "trits."

The Innsbruck group converts a single ultraviolet photon into two photons whose properties are quantum mechanically interlinked, or "entangled." Devices then encode a 0, 1, or 2 onto one of the photons by performing an operation on it (such as flipping its spin or shifting its phase); since the devices are blind to the initial state of the photon, they change the overall properties of the entangled photon pair without determining its final state. The two photons are recombined and then the interlinked pair travels towards a network of detectors. Two-photon interference creates three different sets of detection possibilities in the Innsbruck setup that reveal the quantum state of the entangled pair and whether the photon was encoded with a 0, 1, or 2. The same information contained in a typical ASCII character, normally requiring the use of 8 bits, can be transmitted using only 5 trits.