Beating noise via superposition of order

August 25, 2020

Information can successfully be transmitted through noisy channels using quantum mechanics, according to new research from The University of Queensland and Griffith University.

We all know it's impossible to take a picture through thick smoke or fog--physicists would say, 'it's impossible to send information through a completely noisy channel'.

But UQ physicist Dr Jacqui Romero from the ARC Centre of Excellence for Engineered Quantum Systems (EQUS) said that you can get your picture if you use quantum mechanics, using a principle called 'superposition of order'.

"This is another example of quantum physics assisting classical communication," Dr Romero said.

"Classically, no information can be transmitted through a single completely noisy channel, let alone two completely noisy channels.

"But with quantum mechanics, adding a second channel actually provides a way to successfully get the information through.

"We show that by combining the noisy channels such that you don't know which noisy channel was applied first, it becomes possible to transmit some information."

UQ PhD student Kaumudibikash Goswami, also at EQUS, said that if you're sending information through two noisy media A and B then you would normally think about doing it in an order: either send the information through A, then B, or vice versa.

"The quantum superposition of order means that we lose this idea of an order of events, or of one event causing another," Mr Goswami said.

"This is what allows us to successfully transmit information through the noisy channels.

"More surprisingly, if one medium is noise-free, then superposition of order can completely nullify the effect of the other noisy medium, leading to perfect transmission of information.

"This can be useful in satellite communication as well as secret sharing."
The research is published in Physical Review Research.

University of Queensland

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