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weilawei [soylentnews.org] writes:

Phys.org reports [phys.org],

A team of physicists at the Universities of Bristol, Vienna, the Balearic Islands and the Institute for Quantum Optics and Quantum Information (IQOQI-Vienna) has shown how quantum systems can simultaneously evolve along two opposite time arrows—both forward and backward in time.

The study, published in the latest issue of Communications Physics, necessitates a rethink of how the flow of time is understood and represented in contexts where quantum laws play a crucial role.

Dr. Gonzalo Manzano, co-author from the University of the Balearic Islands, said: "In our work, we quantified the entropy produced by a system evolving in quantum superposition of processes with opposite time arrows. We found this most often results in projecting the system onto a well-defined time's direction, corresponding to the most likely process of the two. And yet, when small amounts of entropy are involved (for instance, when there is so little toothpaste spilled that one could see it being reabsorbed into the tube), then one can physically observe the consequences of the system having evolved along the forward and backward temporal directions at the same time."

Quantum superposition of thermodynamic evolutions with opposing time's arrows, Communications Physics (2021). DOI: 10.1038/s42005-021-00759-1

A preprint [tequantum.eu] of their paper is available.

Original Submission