title: Entanglement between the future and the past in the quantum vacuum.
abstract: We note that massless fields within the future and past light cone may be quantized as independent systems. The vacuum is shown to be a nonseparable state of these systems, exactly mirroring the known entanglement between the spacelike separated Rindler wedges. This leads to a notion of timelike entanglement. We describe an inertial detector which exhibits a thermal response to the vacuum when switched on at t=0, due to this property. The feasibility of detecting this effect is discussed, with natural experimental parameters appearing at the scale of 100 GHz.
authors.affiliation: Centre for Quantum Computing Technology, Department of Physics, University of Queensland, St Lucia, Queensland 4072, Australia. j.olson@physics.uq.edu.au
authors.forename: S Jay
authors.initials: SJ
authors.lastname: Olson
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Ralph