The letter discusses a theoretical framework to understand certain quantum phenomena, which includes simulating hypothetical constructs known as Closed Timelike Curves (CTCs). CTCs in the realm of general relativity are paths through spacetime that, if they could exist, would allow for time loops and, in that sense, "time travel." However, in this letter, CTCs are not being used to propose actual time travel, but are rather a conceptual tool to explore certain quantum behaviors.<p>In the scenario outlined in the paper, the authors simulate CTCs using quantum-teleportation circuits to explore how information can be "sent" back in time, effectively. In other words, they explore a situation where information from the future could be used to amend the state of a quantum system in the past to achieve a metrological advantage. They employ quantum entanglement and post-selection to simulate a scenario where a certain state in a quantum metrology experiment can be determined based on future information, which is then effectively sent back to amend the initial state of the system.<p>The key takeaway is that the authors are not suggesting actual time travel, but are employing the notion of CTCs and quantum simulation to delve into a complex theoretical exploration of quantum metrology. This exploration reveals how entanglement can simulate what would be effects of retrocausality, meaning effects that appear to violate the typical forward flow of cause and effect, to achieve certain advantages in metrology, which is the science of measurement.
From GPT
In essence, this is a very high-level theoretical discussion that uses the concept of time travel as a tool to explore certain quantum phenomena, rather than a proposal or explanation of practical time travel.