Time is one of the most fundamental and mysterious concepts in physics. We all experience time as a stream of events, but what is time in terms of quantum mechanics? Does time exist as an objective reality or is it just an illusion due to the interaction of quantum systems with the environment?

The research was published in the journal Physical Review Letters. The paper’s authors are Sebastian Gemsheim and Jan Rost of the Max Planck Institute for the Physics of Complex Systems in Dresden, Germany. They developed an idea proposed in 1983 by Donald Page and William Wootters. Page and Wootters argued that time appears to an observer who separates himself from the environment and views it as a clock. Thus, time becomes a relative concept, depending on the state of the observer and the environment.

However, Page and Wootters did not take into account the interaction between the observer and the environment, which is inevitably present in real physical systems. Gemsheim and Rost showed that such interaction does not destroy the notion of time as an emergent property but on the contrary makes it more general and universal. They derived the Schrödinger equation for the observer from the energy state of the overall system consisting of the observer, the environment, and their interactions. The Schrödinger equation describes the dynamics of a quantum system over time. Gemsheim and Rost showed that such an equation can be obtained even when the overall system is in steady state, i.e. independent of time. In this case, time appears as a parameter that characterizes the change in the state of the observer under the influence of the environment.

This result is consistent with other concepts of time origins that take into account interactions but use a semi-classical environmental approximation. Gemsheim and Rost do not make such an approximation and consider this medium to be a purely quantum system. This allowed them to take into account the effects of quantum entanglement between the observer and the environment, which can lead to complex and unusual evolutions of the observer. They thus add the missing link to the relativistic theory of time, opening it up to the dynamical phenomena of interacting systems and entangled quantum states.

Gemsheim and Rost’s work does not claim to produce a definitive solution to the time problem in quantum mechanics. Rather, it is an interesting and original contribution to this complex and philosophical subject. It also demonstrates that quantum mechanics can generate new and unexpected concepts that force us to rethink our understanding of reality.

source: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.140202