In classical communications, a bit can represent one of two states - either 0 or 1. But because photons are quantum mechanical objects, they can exist in multiple states at the same time. Photons can also be combined, in a process known as entanglement, to store a bit of quantum information (i.e. a qubit).
Unlike data stored in a computer or sent through conventional fiber optic cables, with qubits a physical kink, the properties of the cable material or even changes in temperature can corrupt a qubit and destroy the information it carries. But now a group lead by Magnus Rådmark at Stockholm University has shown that six entangled photons can encode information that can withstand some wear and tear.
A new method for combining six photons together results in a highly robust qubit capable of transporting quantum information over long distances. Credit: Image courtesy of Carin Cain
Rådmark and his team proved experimentally that their six photon qubits are robust and should be able to reliably carry information over long distances. The technology to encode useful information on the qubits and subsequently read it back is still lacking, but once those problems are solved, we will be well on our way to secure, reliable, and speedy quantum communication.
Their experiment was reported in Physical Review Letters, Physical Review A and Physics.