Bandlimited entanglement harvesting

Abstract

There are many reasons to believe that there is a fundamental minimum length scale below which distances cannot be reliably resolved. One method of constructing a quantum field with a finite minimum length scale is to use bandlimited quantum field theory, where the spacetime is mathematically both continuous and discrete. This is a modification to the field, which has been shown to have many consequences at the level of the field. We consider an operational approach and use a pair of particle detectors (two-level qubits) as a local probe of the field, which are coupled to the vacuum of the bandlimited massless scalar field in a time-dependent way through a switching function. We show that, mathematically, the bandlimit modifies the spatial profile of the detectors so that they are only quasilocal. We explore two different types of switching functions, Gaussian and Dirac delta. We find that, with Gaussian switching, the bandlimit exponentially suppresses the deexcitation of the detectors when the energy gap between the two levels is larger than the bandlimit. If the detectors are prepared in ground state, in certain regions of the parameter space they are able to extract more entanglement from the field than if there was no bandlimit. When the detectors couple with Dirac-delta switching, we show that a particle detector is most sensitive to the bandlimit when it couples to a small but finite region of spacetime. We find that the effects of a bandlimit are detectable using local probes. This work is important because it illustrates the possible observable consequences of a fundamental bandlimit in a quantum field.