TY - JOUR
AB - In all our well-established theories, it is assumed that events are embedded in a global causal structure such that, for every pair of events, the causal order between them is always fixed. However, the possible interplay between quantum mechanics and general relativity may require a revision of this paradigm. The process matrix framework keeps the validity of quantum physics locally but does not assume the existence of a global causal order. It allows to describe causal structures corresponding to a quantum superposition of ‘A is before B’ and ‘B is before A’. So far, the framework has been developed only for finite-dimensional systems, and a straightforward generalization to infinite dimensions leads to singularities. Such generalization is necessary for continuous-variable systems and is a prerequisite for quantum fields on indefinite causal structures. Here we develop the process-matrix framework for continuous-variable systems. We encounter and solve the problems of singularities. Moreover, we study an example of a process in infinite dimensions, and we derive correlations exhibiting intereference due to processes in which A is before B and B is before A.
AU - Giacomini, F.
AU - Castro-Ruiz, E.
AU - Brukner, Č.
DA - 2016/11/16/
DO - 10.1088/1367-2630/18/11/113026
JF - New Journal of Physics
PY - 2016
SE - 2016/05/24/
SP - 113026
TI - Indefinite causal structures for continuous-variable systems
UR - http://iopscience.iop.org/article/10.1088/1367-2630/18/11/113026/pdf
VL - 18
ER -