Collection Number C21004
Collection Date -
Collection Type Conference/School
In physics, a reference frame is an abstract coordinate system that specifies observations within that frame. While quantum states depend on the choice of reference frame, the form of physical laws is assumed to be covariant. Recently, it has been proposed to consider reference frames as physical systems and as such assume that they obey quantum mechanics. In my talk, I will present recent results in the field of "quantum reference frames" (QRF).
"The process matrix framework was invented to capture a phenomenon known as indefinite or quantum causal structure. Due to the generality of that framework, however, for many process matrices there is no clear physical interpretation. A popular approach towards a quantum theory of gravity is the Page-Wootters formalism, which associates to time a Hilbert space structure similar to spatial position. By explicitly introducing a quantum clock, it allows to describe time-evolution of systems via correlations between this clock and said systems encoded in history states.
"Spatio-temporal relations are often taken to be more primitive than causal relations. Such a relationship is assumed whenever it is suggested that it is part of the definition of a causal relation that the cause must precede the effect in time. There are good reasons, however, to take causation to be the more primitive notion, with spatio-temporal relations merely describing aspects of causal relations.
The kappa-Minkowski noncommutative spacetime has been studied for a long time as an example of quantum spacetime with nontrivial commutation relations between spatial and temporal coordinates which, at first sight, seem to break Poincaré invariance. However kappa-Minkowski is invariant under a Hopf-algebra deformation of the Poincaré group, which involves some noncommutative structures that prevent the sharp localization of reference frames.
Composite quantum particles as ideal quantum clocks — operational approach to quantum aspects of time
In general relativity time requires an operational description, for example, associated with the reading of an idealised clock following some world line. I will show that in quantum physics idealised clocks can be modelled as composite quantum particles and discuss what foundational insights into the notion of time is enabled by this approach.