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Research in the field of Relativistic Quantum Information (RQI) brings together the two pillars of modern physics: quantum theory and general relativity. RQI research is yielding results ranging from new insights into the laws of nature to concrete applications in quantum computing and quantum communications.

Postdoctoral fellow Aharon Brodutch at the Institute for Quantum Computing (IQC) investigates an area of RQI that involves the interaction between weak gravity (such as that of the earth) and photons. Recently, Brodutch collaborated with colleagues from the University of ��ݮ��Ƶ and Macquarie University, Australia, to determine the set-up of a satellite experiment that detects gravitational effects on the quantum degrees of freedom of a photon.  

The researchers considered a theoretical interferometer in space to find the measurement precision needed to detect the effect of gravity on a photon traveling along a beam of light. Using one satellite and two different paths of light rays going to the satellite using time delays, they found that in terms of polarization the gravitational effect is too small to be measured with an interferometer.

The next theoretical experiment considered a phase-shift in the interferometer. Instead of looking at polarization, the focus was on the phase of the photon going through two different arms. In this experiment for a realistic satellite mission, Brodutch and collaborators found that a phase difference is measureable. After accounting for realistic problems, such as the movement of the satellite and other relativistic effects, the theoretical experiment is extremely close to practical implementation.

“The next step will be tackling more realistic problems, like atmosphere and stabilizing the pathways of the interferometer,” says Brodutch. “This is the most optimistic result in terms of experimental feasibility.”

, the third paper in this series, appeared in Physical Review D in March.

Also in March, a second paper by Brodutch appeared; this time in Physical Review Letters. Brodutch provided a modified calculation in a published .��