COLLOQUIUM: Quantum Physics: A Possible Theory of the World as a Whole (March 2017)

Описание: Speaker: Vlatko Vedral, CQT, NUS

Abstract:
Quantum mechanics is commonly said to be a theory of microscopic things: molecules, atoms, subatomic particles. Most physicists, though, think it applies to everything, no matter what the size. The reason its distinctive features tend to be hidden is not a simple matter of scale. Over the past few years experimentalists have seen quantum effects in a growing number of macroscopic systems. The quintessential quantum effect, entanglement, can even occur in large systems as well as warm ones - including living organisms - even though molecular jiggling might be expected to disrupt entanglement.

I will discuss how techniques from information theory, quantum and statistical physics, can all be combined to elucidate the physics of macroscopic objects. Can it be that part of the macroscopic world is quantum, while the rest is, in some sense, classical? This question is also of fundamental importance to the development of future quantum technologies, whose behavior takes place invariably in the macroscopic non-equilibrium quantum regime.

I will discuss the concept of quantum macroscopicity and argue that it should be quantified in terms of coherence based on a set of conditions that should be satisfied by any measure of macroscopic coherence. I will show that this enables a rigorous justification of a previously proposed measure of macroscopicity based on the quantum Fisher information. This might shed new light on the standard Schrödinger cat type interference experiment that is meant to demonstrate the existence of macroscopic superpositions and entanglement.