A way forward for fundamental physics in space

Abstract

Space-based research can provide a major leap forward in the study of key open questions in the fundamental physics domain. They include the validity of Einstein’s Equivalence principle, the origin and the nature of dark matter and dark energy, decoherence and collapse models in quantum mechanics, and the physics of quantum many-body systems. Cold-atom sensors and quantum technologies have drastically changed the approach to precision measurements. Atomic clocks and atom interferometers as well as classical and quantum links can be used to measure tiny variations of the space-time metric, elusive accelerations, and faint forces to test our knowledge of the physical laws ruling the Universe. In space, such instruments can benefit from unique conditions that allow improving both their precision and the signal to be measured. In this paper, we discuss the scientific priorities of a space-based research program in fundamental physics.

Emergence of Classicality in Stern–Gerlach Experiment via Self‐Gravity

“…We believe this experimental test should be easier to implement compared to the interference experiments which are being attempted on the mesoscopic scale. [37][38][39]…”

Gravitational Redshift Induces Quantum Interference

“…These effects might be due to, for example, asymmetries as a consequence of anisotropic background spacetimes (effects that can be witnessed by comparing results from experiments with photons propagating in different directions), an ultraviolet cutoff or coarse graining of spacetime among many. [ 44 ] In this case, propagation through a long baseline can provide the necessary cumulation of effects that can lead to successful detection. Since the mode‐mixing predicted here is a definitive signature of quantum field theory in curved spacetime, any deviation could be amplified in an interferometric‐like measurement and therefore detected.…”

“…To date, there are many experiments that have been already performed, and more are planned. [42][43][44] An even more compelling problem is the validity of the EEP in the quantum domain. While it is implicitly assumed that it does apply, there are different arguments why testing it for free falling quantum systems would be greatly beneficial for our current understanding.…”

Interaction between Everett worlds and fundamental decoherence in Non-unitary Newtonian Gravity

“…Viable platforms for large-mass experiments include non-interferometric opto-and magneto-mechanical systems [31,32] and matter-wave interferometers with molecules and nanoparticles [33], while ground-to space optical links, such as the entangled-photon pairs of the Space QUEST mission [34] and the long-baseline quantum links proposed in the context of the DSQL mission [35], are currently pursued because of the peculiar experimental conditions with respect to the ground (see for a detailed account Ref. [36] and references therein). Finally, a novel underground experiment in operation at Gran Sasso National Laboratory [19] is very promising as well thanks to a reduced exposition to cosmic radiation.…”