The laws of quantum mechanics could help to transmit classical ? or binary ? information more efficiently, suggests a paper online this week in Nature Physics. This finding solves a problem considered to be one of the most important open questions in the field of quantum information theory ? can the effects of quantum mechanics be harnessed for sending classical ‘bits of information?’

In recent years, there has been intense research activities aimed at using quantum-mechanical effects ? which govern the behaviour of particles at the smallest length scales ? for the purposes of communication and computation. A key property that has been harnessed is known as quantum entanglement, but it has been unclear whether this can help transmit classical information efficiently through quantum communication channels. Several conjectures say that quantum entanglement is of no help in such situations.

Matthew Hastings now shows, on a fundamental level, that these conjectures are false. The practical significance of these findings remains to be shown, however they will be of immediate relevance to how the capacity of quantum communication channels can be calculated, and therefore for predicting in which communication tasks quantum effects can be of potential use.