Dear Colleagues,

The most fundamental understanding that we have of nature is given by quantum mechanics, for small length scales, and by general relativity in the large length regime. However, the inability to unify the underlying concepts of these two theories remains one of the biggest unsolved problems in physics. Fortunately, a new generation of experiments is quickly developing and promise to provide deeper insights into the interface between gravity and quantum theory. This includes the study of large quantum superposition states involving clocks or increasingly massive objects, space-based quantum experiments, and the measurement of gravitational parameters at smaller (laboratory) length scales using quantum systems, such as cold neutrons and atoms. Recently, there has been fast progress in the high-sensitivity measurements of the Newtonian constant, of the gravity field-gradient and curvature and of short-range gravitational forces. There have even been proposals to use these systems to measure gravitational waves and demonstrate quantum field theory in curved space–time. Gravitational waves have been recently detected and quantum optics has been playing a central role in the most advanced experiments. However, we are still lacking experiments that help us understand general relativity at small lengths or large energies where quantum effects become relevant.

This Special Issue of Atoms will highlight theory and experiments that aim at measuring gravitational effects in the laboratory focusing on the latest updates in topics, such as measurements of gravitational waves, quantum tests of the equivalence principle, quantum metrology for gravitational fields and space-based quantum experiments. This includes classical and quantum methods with an open interdisciplinary scope.

Dr. Ivette Fuentes
Dr. Philippe Bouyer
Guest Editors

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