Quantum Communications are based on degrees of freedom (DoF) of light that allow for the sharing of
quantum states over long distances. The DoF for Space links are of interest to address the interplay of Quantum
Physics and Gravity as well as the applications as QKD on very long scales.
We shall describe some steps forward in the use of temporal modes for free-space Quantum Communications
(QC). These were initially used to investigate the superposition principle on a Space channel [1,2] and are
recently considered for an Optical Test of the Einstein Equivalence Principle [3].
A relevant development in the Lab use of the temporal modes includes the introduction of a scheme free from
the post-selection loophole, when entangled stated, that may be extended to free-space channels [4]. Moreover,
the experimental efforts to improve both the resolution in the temporal detection and the photon exchange scale
has now reached the level of 250 ps along a real space channel [5] and the altitude of 20000 km [6]
respectively, as well the Space extension of the John Wheeler wave-particle Gedankenexperiment [7].
The QC experiments along Space channels were realized at MLRO - Matera Laser Ranging Observatory of the
ASI Italian Space Agency, in Matera, Italy.
References:
[1] G. Vallone, D. Dequal, M. Tomasin, F. Vedovato, M. Schiavon, V. Luceri, G. Bianco, and P. Villoresi,
“Interference at the Single Photon Level Along Satellite-Ground Channels,” Phys. Rev. Lett., vol. 116, no. 25,
p. 253601, Jun. 2016.
[2] C. Agnesi, F. Vedovato, M. Schiavon, D. Dequal, L. Calderaro, M. Tomasin, D. G. Marangon, A. Stanco, V.
Luceri, G. Bianco, G. Vallone, and P. Villoresi, “Exploring the boundaries of quantum mechanics: advances in
satellite quantum communications,” Philos. Trans. R. Soc. A Math. Phys. Eng. Sci., vol. 376, no. 2123, p.
20170461, May 2018.
[3] D. R. Terno, F. Vedovato, M. Schiavon, A. R. H. Smith, P. Magnani, G. Vallone, and P. Villoresi, “Proposal
for an Optical Test of the Einstein Equivalence Principle,” arXiv Prepr., p. 1811.04835, Nov. 2018.
[4] F. Vedovato, C. Agnesi, M. Tomasin, M. Avesani, J.-Å. Larsson, G. Vallone, and P. Villoresi,
“Postselection-Loophole-Free Bell Violation with Genuine Time-Bin Entanglement,” Phys. Rev. Lett., vol.
121, no. 19, p. 190401, Nov. 2018.
[5] C. Agnesi, L. Calderaro, D. Dequal, F. Vedovato, M. Schiavon, A. Santamato, V. Luceri, G. Bianco, G.
Vallone, and P. Villoresi, “Sub-ns timing accuracy for satellite quantum communications,” J. Opt. Soc. Am. B,
vol. 36, no. 3, p. B59, Mar. 2019.
[6] L. Calderaro, C. Agnesi, D. Dequal, F. Vedovato, M. Schiavon, A. Santamato, V. Luceri, G. Bianco, G.
Vallone, and P. Villoresi, “Towards quantum communication from global navigation satellite system,” Quantum
Sci. Technol., vol. 4, no. 1, p. 015012, Dec. 2018.
[7] F. Vedovato, C. Agnesi, M. Schiavon, D. Dequal, L. Calderaro, M. Tomasin, D. G. Marangon, A. Stanco, V.
Luceri, G. Bianco, G. Vallone, and P. Villoresi, “Extending Wheeler’s delayed-choice experiment to space,”
Sci. Adv., vol. 3, no. 10, p. e1701180, Oct. 2017.