‘Perfect entanglement’ of two light beams has opened a major step towards highly secure quantum communication systems.

The University of Queensland’s Professor Tim Ralph and his colleagues from Canada and Russia have developed a technique to restore entangled light beams that have been distributed between distant points.

“We have experimentally demonstrated a technique whereby entangled light beams can be distributed between distant parties even though a large amount of loss is introduced,” Tim says.

“In particular, we were able to restore entanglement, which had been sent through a channel with 95 per cent loss, back to its original value.”

Two light beams are entangled when they are so strongly correlated that their behaviour defies normal explanations – what Einstein called ‘spooky’.

However, quantum entanglement can be lost when the light beams are transmitted from one place to another.

By resolving the loss issue, Tim and his team have enhanced entanglement’s ability to be distributed as an unbreakable key to encrypt information.

“When you use entanglement to share a key with which to encrypt your information, then you can ensure that nobody else has the key. You can distribute that key – but nobody can copy it,” Tim says.

“Entanglement means privacy. By using perfect entanglement, it’s impossible for anyone else to have the same string of numbers as the string of numbers you share with your friend.”

The team hopes to apply this benchmark research to a range of quantum technologies, including communication systems, quantum computers and quantum sensors.

Banner image:  Tim discusses the issue of entanglement with his PhD student Josephine Dias.
Credit:  Kaerin Gardner