Perceiving the flow of time requires the happening of events and their detection by the observer. This proposal explores the implication of quantum mechanics on the perception of the passage of time. It focuses on the role played by quantum speed limits (QSL),
a set fundamental bounds that regulate the pace of quantum evolution in Nature at which complexity can emerge. Indeed, QSL determine the minimum time scale for something to happen. In other words, no event can be recorded in a time scale smaller than that dictated by QSL. As a result, we expect QSL to govern the flow of time, and in doing so, the subjective experience in the perception of reality.

Currently available QSL are however “too conservative” and fail to capture the evolution of observable reality, e.g. they are extensive on the system size and become trivial for large systems. Rare is the observation, by either a classical or quantum being, that probes directly the speed of evolution of a quantum state. Rather, observers in the Universe register (snapshots of) the time evolution of a set of observables (the properties of the system being measured). In this project we shall unveil universal QSL to the evolution of quantum observables that depend not only on the system of interest but also on the perceiving being. We will explore the implications of QSL in the perception of the passage of time and reality for a local observer and at cosmological level.

Specifically: (i) QSL for arbitrary observables in both isolated and open quantum systems will be derived. (ii) These bounds will be used to analyze the emergence of classical behavior from a quantum substrate, as well as the generation of quantumness during the evolution of a quantum being. (iii) Combining QSL and full quantum dynamics, the decay of an unstable composite system will be fully characterized and used to discuss cosmological implications on the history of an unstable universe.