Andrea Tononi (ICFO, Barcelona, Spain)
Description
Temporal Bell inequalities in a many-body system
We formulate a temporal Clauser-Horne inequality by considering two parties choosing two observables to measure at different consecutive times. For two entangled antipodal spins joined by a spin chain, we show that the inequality is violated during a small finite time interval between the measurements. This fact contrasts with the time evolution in vacuum, which is describable in terms of a hidden-variable theory. Our result demonstrates that the finite velocity for quantum information spreading in the chain prevents signaling and therefore the immediate vanishing of quantumness.