Reversing The Flow Of Time

Dr. S.S. Verma, Department of Physics, S.L.I.E.T., Longowal, Distt-Sangrur (Punjab)-148106

2019-03-19 09:13:18



Nature has designed the time to always move in forward direction only. We live in the present only for an undefined smallest fraction of it (time).  Every passing moment is designated as past and every moment of time to come is termed as future.  We know our past but still always eager to know about the future. Man has always desired to move into past and future at his own wish.   Moving into immediate future is an inevitable natural process but in distant future has not been possible.  Traversing into past is only possible in memories but time cannot be made to flow in reverse direction.

The changes we notice over the years vividly illustrate science's​ "arrow of  time" - the likely progression from order to disorder. We cannot reverse this arrow any more than we can erase all our wrinkles or restore a shattered teacup to its original form. Scientists and technologists have always boggled for human control on time flow but without any success so far.  But in a recent article, scientists have reported that quantum simulation gives a sneak peek into the possibilities of time reversal. An international team of scientists led by the U.S. Department of Energy's (DOE) Argonne National Laboratory explored this question in a first-of-its-kind experiment, managing to return a computer briefly to the past. The results suggest new paths for exploring the backward flow of time in quantum systems. They also open new possibilities for quantum computer program testing and error correction.

To achieve the time reversal, the research team developed an algorithm for IBM's public quantum computer that simulates the scattering of a particle. In classical physics, this might appear as a billiard ball struck by a cue, traveling in a line. But in the quantum world, one scattered particle takes on a fractured quality, spreading in multiple directions. To reverse its quantum evolution is like reversing the rings created when a stone is thrown into a pond. In nature, restoring this particle back to its original state  in essence, putting the broken teacup back together  is impossible. The main problem is need of a "supersystem," or external force, to manipulate the particle's quantum waves at every point. Researchers also note that the timeline required for this supersystem to spontaneously appear and properly manipulate the quantum waves would extend longer than that of the universe itself. In order to overcome this complexity the research team set out their algorithm to simulate an electron scattering by a two-level quantum system, "impersonated" by a quantum computer qubit  the basic unit of quantum information  and its related evolution in time. The electron goes from a localized, or "seen," state, to a scattered one. Then the algorithm throws the process in reverse, and the particle returns to its initial state  in other words, it moves back in time, if only by a tiny fraction of a second.

Given that quantum mechanics is governed by probability rather than certainty, the odds for achieving this time-travel feat were pretty good: The algorithm delivered the same result 85 percent of the time in a two-qubit quantum computer. The result deepens our understanding of how the second law of thermodynamics  that a system will always move from order to entropy and not the other way around  acts in the quantum world. The researchers demonstrated in previous work that, by teleporting information, a local violation of the second law was possible in a quantum system separated into remote parts that could balance each other out. The results also give a nod to the idea that irreversibility results from measurement, highlighting the role that the concept of ‘measurement’ plays in the very foundation of quantum physics. The finding may eventually enable better methods of error correction on quantum computers, where accumulated glitches generate heat and beget new ones. A quantum computer able to effectively jump back and clean up errors as it works could operate far more efficiently.