Quantum error correcting code discovered

The computers of the future, currently developed in many laboratories worldwide, will use increasingly miniaturized components. The ultimate stage of this development is expected to reply on the manipulation of quantum bits, analogous to bits -- the computer's 0 and 1's -- but at the level of atoms and photons, which are the elementary constituents of matter and light. Quantum physics prevails at the microscopic scale, so that quantum computers, which would exploit information quanta at this scale, are some of the most awaited applications of this new information technology.

The article by Mikael Lassen and collaborators reports on an important future component for quantum information technology, namely a quantum error correcting code.

We actually use error correcting codes every day without knowing it ! CDs and DVDs use this technique to enable a reading that is relatively insensitive to small imperfections on the disk surface such as scratches, smudges or dust.

The Danish team and its Belgian and German colleagues have implemented an error correcting code that provides resistance to errors in the handling, transmission or storage of quanta of information. Their scheme, using the transmission of photons, resists the loss thereof. Quantum information is split into several light beams and can be recovered even if photons of these beams have been lost.

Such an insensitivity is remarkable as information quanta are deemed extremely fragile: the loss of one or a few photons, almost imperceptible particles of light constituting a beam, is an often inevitable process.

This experiment is one of the first demonstration of error correction achieved at the scale of quanta and should help paving the way to computers of the future.