Can tachyons explain all possible nonlocal effects?
Abstract:
Ever since quantum nonlocal correlations were empirically realised through violations of Bell inequalities, two distinct lines of research have emerged. One natural direction posits underlying mechanisms, in particular models in which superluminal influences, which we refer to as tachyons, propagate between distant entangled particles within a privileged frame. The other focuses on identifying the classes of phenomena that are non-signalling. In this latter approach it has been realised that nonlocal correlations can, in principle, be tampered with by a third party who is spacelike separated from the local measurement sites. This nonlocal effect is termed jamming: the correlations are ‘jammed’ by the jammer via an action at a distance without generating closed causal loops.
In this seminar, I will introduce delayed-choice jamming, in which the jammer's choice, made in the future of all local measurements, rewrites the past record of outcomes and decides whether the distant data reveals nonlocality, while remaining non-signalling. We then ask whether a model in which tachyons travel in a privileged frame can account for this phenomenon, and we show that it fails in every conceivable privileged frame. Thus no theory of tachyons can reproduce all nonlocal effects. The particulars of the frame are secondary. Our analysis is instead driven by dimensionality and symmetry, manifesting in the form of Platonic duality. The implications of our results extend to clarifying what non-signalling and non-locality mean.