Towards communication in a curved spacetime geometry

Abstract

The current race in quantum communication – endeavouring to establish a global quantum network – must account for special and general relativistic effects. The well-studied general relativistic effects include Shapiro time-delay, gravitational lensing, and frame dragging which all are due to how a mass distribution alters geodesics. Here, we report how the curvature of spacetime geometry affects the propagation of information carriers along an arbitrary geodesic. An explicit expression for the distortion onto the carrier wavefunction in terms of the Riemann curvature is obtained. Furthermore, we investigate this distortion for anti de Sitter and Schwarzschild geometries. For instance, the spacetime curvature causes a 0.10 radian phase-shift for communication between Earth and the International Space Station on a monochromatic laser beam and quadrupole astigmatism; can cause a 12.2% cross-talk between structured modes traversing through the solar system. Our finding shows that this gravitational distortion is significant, and it needs to be either pre- or post-corrected at the sender or receiver to retrieve the information.

Observer dependence of photon bunching: The influence of the relativistic redshift on Hong-Ou-Mandel interference

“…In the past decade a new body of work has developed the theory of photons propagating in (weakly) curved spacetime from different perspectives [14,15,29,30]. We assume that a photon can be indeed modelled by using a massless scalar field, and that it is effectively strongly confined to the direction of propagation in a (weakly curved) static spacetime.…”

“…We assume that a photon can be indeed modelled by using a massless scalar field, and that it is effectively strongly confined to the direction of propagation in a (weakly curved) static spacetime. In this way, we can effectively assume that the photon is localized along a litghtlike path, and therefore we can ignore the deformation effects that occur in the perpendicular directions [29,30]. Nevertheless, we expect that the gravitational redshift will still affect the photon, and this effect in the context of a localized wavepacket has been pioneered in the literature [14,15].…”

“…We employ Equations ( 26),( 28) and (29) to obtain the relation between the interference patterns obtained by two distinct observer pairs…”

Light propagation and atom interferometry in gravity and dilaton fields

“…Similarly, in light-pulse atom interferometers [25,26,52] matter propagates within dilaton fields and consequently such devices are susceptible [53] to both EPP violations [19-21, 23, 54] and dark matter [16][17][18]22]. However, with light pulses being an essential tool to manipulate the atoms, their modified behavior in gravity [55][56][57][58][59][60][61] and dilaton fields has to be taken into account for a consistent description of such experiments.…”

Gravitational redshift induces quantum interference

“…A realistic photon is characterized by a finite bandwidth, instead of an (infinitely) sharp frequency. We assume that we can discard all effects due to the extension of the photon along directions that are orthogonal to that of propagation, and that these can be taken into account separately [26]. A photon operator is therefore constructed as Âω0 := ∞ 0 dωF ω0 (ω/σ) âω , where the (complex) function F ω0 (ω/σ) determines the frequency profile.…”