Physicists develop theories for particular regimes. As an example, general relativity describes the Universe at large scales: experiments probed its validity at distances in range from the cosmic scale and up to several meters. In contrast, quantum mechanics describes physics at the lower scales. We have verified its laws at the smallest currently obtainable distances (Large Hadron collider experiments) and in range up to hundreds of kilometers. However, we expect to see many new interesting effects at the intersection of quantum and relativistic regimes. It may provide us more clues on the “last big mystery” of modern physics – quantum gravity.
In http://arxiv.org/pdf/1206.4949v2.pdf, authors propose tests with artificial satellites to probe quantum mechanics on larger scales (length scales in suggested experiments are close to the radius of curvature of spacetime). Physicists hope to perform their tests in the near future and obtain valuable insights on the interplay between quantum phenomena and gravity. Technology is not avanced enough to enable such experiments; scientists can only outline basic ingredients, provide a roadmap and estimate potentially observable phenomena in experiments with artificial satellites (both in Earth orbit and in the rest of the solar system).
In general, we could divide suggested experiments into several categories. Some of them would examine well-known physics in a new regime. Physicists encountered several revelations in their understanding of nature by probing old theories in a new regime. Scientists would either obtain unexpected results even for well-established theories or prove their validity at the larger scales. Other experiments aim to provide more answers for physical phenomena on which our knowledge is uncertain. We already hypothesize possible outcomes for such experiments, but there is no proof even in the standard regime of the theory (the parallel transport of spins in curved spacetime). A third class would examine whether alternative theories for the specific regime are better or worse than the conventional approach. Last is meaningful, as in the already probed regime, all theories provide the same outcomes. The final category contains tests that search for new phenomena that is unexplainable by any standard theory and lead to new physics.
All these sorts of experiments could be subdivided according to the particular phenomena involved. The first group contains entanglement tests – mostly variations of the Bell’s experiment. These tests are most approachable in the near future. Other groups of experiments probe relativistic effects in the quantum information theory, quantum-field theories in non-inertial frames, quantum gravity and quantum communication.
This work provides a concise guide to the most important experiments in quantum mechanics and relativity for the future as the authors – most prominent experimentalists and theoreticians in the field – see it. I’ve definitely enjoyed this reading.