IQC Research Assistant Professor Eduardo Martin-Martinez, in collaboration with PhD student Robert Jonsson and Professor Achim Kempf, both of the Department of Applied Mathematics at the University of Waterloo, have found a possible communication channel that does not require energy transmission from the sender to the receiver, but instead requires only the receiver to spend energy to run its detector, similar to a collect call.
They found that any interaction of matter with a massless quantum field produces a perturbation – like an echo – that could travel more slowly than the speed of light. This is unlike typical communication, which is done via the emission and absorption of light. This echo can be used to transmit information, an effect that is made possible with quantum fields of certain dimension or in the presence of space time curvature. Since it is the receiver who spends the energy to read the information carried in the echo, this kind of communication without energy exchange may be called “Quantum Collect Calling.” This new type of communication channel makes it possible for the sender to transmit information without energy exchange, without the receiver being present and without spending extra energy to broadcast to many receivers. The paper, Information Transmission Without Energy Exchange, was published in Physical Review Letters March 20.
Martin-Martinez and collaborators (A. Blasco, L.J. Garay and M. Martin-Benito) have already taken the next step to see if this new type of communication channel can be used to look more closely at the early stages of the universe by accessing information that was previously inaccessible. Their fundamental results, A glimpse of the early universe without real light, show that information transmitted through these echoes travels more resiliently than it would by light, only showing signs of decay over time. Remarkably, they also showed that, in a matter-dominated universe, the information does not decay at all as a function of distance between the sender and receiver. Echoes traveling from the very start of the universe could shed some light on this event, providing helpful insight for cosmologists.
“Information about background signals from the early universe will also be propagated through this echo. The challenge (now) is to figure out precisely what form the echoes will take and how to build receivers that can pick them up,” Martin-Martinez told New Scientist in January.
The published paper, titled Violation of the Strong Huygen's Principle and Timelike Signals from the Early Universe appeared in Physical Review LettersApril 7.
Martin-Martinez, also a visiting fellow at the Perimeter Institute for Theoretical Physics, is one of the few researchers in Canada exploring Relativistic Quantum Information (RQI), a multidisciplinary field that combines general relativity with quantum information theory. He brings relativistic approaches to quantum information research and uses quantum theories to explore relativity and the structure of space time.