## SPACE-BASED RELATIVISTIC & QUANTUM SCIENCE

QKD explains how you and I can exchange information and make sure that only the two of us can access it. In addition, we would like to know if somebody is messing around with the information we are exchanging. QKD offers a recipe, based on quantum mechanics, which allows us to do this! What we need to do is share a secret

*key*, which allows us (and only us) to encode and decode any information we exchange. There are clever protocols which allow us to share the secret key (the original BB84 is described in [5]) and there are companies that now sell technology based on these principles!

Furthermore, ICT roadmaps of different countries envision that going to space is the future for quantum (and perhaps relativistic?) technologies [6].

I have investigated the effects of gravity on quantum communication schemes. The research was partly inspired by [7]. I was able to show that if a user on the earth tries to exchange a secret key with a user on a spaceship, for example the International Space Station (ISS), the key will be affected by the curvature of space-time around the Earth and these effects are measurable with current technology.

Furthermore, we have shown that by employing relativistic quantum metrology, one can aim at exploiting the effects described above for ultra-precise measurements of relevant parameters, such as distances in a future quantum GPS.

## References

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- "Lorentz Invariance of Entanglement", P. M. Alsing, G. J. Milburn, arXiv:quant-ph/0203051v1 (2002)
- "Quantum Entropy", A. Peres, P. F. Scudo, D. R. Terno, Physical Review Letters 88: 230402 (2002)
- "Notes on black-hole evaporation". W.G. Unruh, Physical Review D 14 (4): 870 (1976)
- "Quantum Cryptography: Public key distribution and coin tossing", C. H. Bennett and G. Brassard, Proceedings of the IEEE International Conference on Computers, Systems, and Signal Processing, Bangalore, p. 175 (1984)
- Quantum Information and Communication European roadmap: http://qurope.eu/projects/quie2t/wp2/deliverables;

Roadmap of Quantum ICT Laboratory of National Institute of Information and Communications Technology of Japan: http://www.nict.go.jp/en/advanced\_ict/quantum/roadmap.html;

Quantum Information Science and Technology Roadmap of USA: http://qist.lanl.gov/qcomp\_map.shtml - "Quantum communication with an accelerated partner", T. G. Downes, T. C. Ralph and N. Walk, Phys. Rev. A 87, 012327 (2013)
- "Black hole explosions?", Hawking, S. W., Nature 248 (5443): 30 (1974).
- "Experimental black hole evaporation”, Unruh, W.G., Phys. Rev. Lett., 46, 1351–1353, (1981).