The Arrow of Time, or Time's Arrow, is a concept developed in 1927 by the British astronomer Arthur Eddington involving the "one-way direction" or "asymmetry" of time. This direction, according to Eddington, can be determined by studying the organization of atoms, molecules, and bodies, might be drawn upon a four-dimensional relativistic map of the world ("a solid block of paper").

Physical processes at the microscopic level are believed to be either entirely or mostly time-symmetric: if the direction of time were to reverse, the theoretical statements that describe them would remain true. Yet at the macroscopic level[when defined as?] it often appears that this is not the case: there is an obvious direction (or flow) of time. Read more

Time-reversal of an unknown quantum state   PhysOrg - August 11, 2020
Physicists have long sought to understand the irreversibility of the surrounding world and have credited its emergence to the time - symmetric, fundamental laws of physics. According to quantum mechanics, the final irreversibility of conceptual time reversal requires extremely intricate and implausible scenarios that are unlikely to spontaneously occur in nature. Physicists had previously shown that while time-reversibility is exponentially improbable in a natural environment - it is possible to design an algorithm to artificially reverse a time arrow to a known or given state within an IBM quantum computer. However, this version of the reversed arrow-of-time only embraced a known quantum state and is therefore compared to the quantum version of pressing rewind on a video to "reverse the flow of time."

Arrow of time: New understanding of causality, free choice, and why we remember the past but not the future   Science Daily - July 28, 2015
Theoretical physicists have developed a fully-symmetric formulation of quantum theory which establishes an exact link between asymmetry and the fact that we can remember the past but not the future. The laws of classical mechanics are independent of the direction of time, but whether the same is true in quantum mechanics has been a subject of debate. While it is agreed that the laws that govern isolated quantum systems are time-symmetric, measurement changes the state of a system according to rules that only appear to hold forward in time, and there is difference in opinion about the interpretation of this effect. Now theoretical physicists have developed a fully time-symmetric formulation of quantum theory which establishes an exact link between this asymmetry and the fact that we can remember the past but not the future -- a phenomenon that physicist Stephen Hawking has named the "psychological" arrow of time. The laws of classical mechanics are independent of the direction of time, but whether the same is true in quantum mechanics has been a subject of debate. While it is agreed that the laws that govern isolated quantum systems are time-symmetric, measurement changes the state of a system according to rules that only appear to hold forward in time, and there is difference in opinion about the interpretation of this effect.