Alice and Bob in an expanding spacetime

¹ Universidade Federal de Minas Gerais, Departamento de Física, ICEX - P.O. BOX 702, 30.161-970, Belo Horizonte, MG, Brazil
² Universidade Federal de Ouro Preto, Departamento de Matemática, ICEB - Campus Morro do Cruzeiro, s/n, 35400-000, Ouro Preto, MG, Brazil
³ Department of Mathematical Sciences, Centre for Particle Theory, Durham University - South Road, Durham DH1 3LE, UK

^(a) helder@fisica.ufmg.br (corresponding author)
^(b) gdesouza@iceb.ufop.br
^(c) p.r.w.mansfield@durham.ac.uk
^(d) msampaio@fisica.ufmg.br

Received: 14 August 2015
Accepted: 11 September 2015

Abstract

We investigate the teleportation of a qubit between two observers Alice and Bob in an asymptotically flat Robertson-Walker expanding spacetime. We use scalar or fermionic field modes inside Alice's and Bob's ideal cavities and show the degradation of the teleportation quality, as measured by the fidelity, through a mechanism governed by spacetime expansion. This reduction is demonstrated to increase with the rapidity of the expansion and to be highly sensitive to the coupling of the field to spacetime curvature, becoming considerably stronger as it reduces from conformal to minimal. We explore a perturbative approach in the cosmological parameters to compute the Bogoliubov coefficients in order to evaluate and compare the fidelity degradation of fermionic and scalar fields.