Researchers have proposed a theoretical approach that could allow messages to be sent into the past using principles from quantum mechanics. Indeed, it could be happening right now already!
The concept does not enable physical travel through time but focuses on information transfer through causal loops at the quantum scale.
The work, accepted for publication in Physical Review Letters, builds on ideas from general relativity and quantum entanglement.
It draws a parallel to the causal loop depicted in Christopher Nolan’s film Interstellar, where a message is sent to the past via a watch.
Co-author Dr Kaiyuan Ji, a researcher at Cornell University, told New Scientist: “The father remembers how the daughter decodes his future message. So he can instruct himself on what is the best way to encode the message.”
Professor Seth Lloyd of the Massachusetts Institute of Technology (MIT) described an earlier related experiment from 2010: “It was the equivalent of sending a photon a few nanoseconds backwards in time, and having it try to kill its former self.”
Lloyd noted the practical challenges: “Nobody’s built an actual physical, closed time-like curve, and there are reasons to think it’s very hard to make one. But all channels are noisy.”
The paper explains how prior knowledge of how a message was decoded could improve encoding in the future: “The father, who is in the future, may retrieve his memory of past events he has witnessed, even including the daughter’s decoding of the message which he is about to send! It would thus not be surprising that he will consult his memory of the daughter’s decoding when encoding his message, so as to maximize the efficiency of the communication.”
According to the research, this approach could make backward time messages clearer than those sent forward in normal time, even over noisy channels.
The team suggests the idea could be tested experimentally at the quantum level and may offer insights into communication through noisy systems.
The concept relies on closed time-like curves (CTCs), paths allowed by general relativity where something could theoretically return to its own past.
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