Dear Colleagues,

With the development of ultracold atom experimental technology, ultracold atoms provide an excellent research platform for many-body quantum physics and quantum precision measurements. Using the well-developed quantum control technology, people can study many novel many-body quantum effects based on ultracold atomic systems, and can prepare and manipulate some non-Gaussian multi-particle entangled states that can be used for quantum precision measurement.

This Special Issue invites contributions reporting on the basic research on of cold atoms and applications in precision measurements. Moreover, contributions should fall within the scope of the journal Symmetry.

Prof. Dr. Wuming Liu
Dr. Xiaofei Zhang
Prof. Dr. Chaofei Liu
Guest Editors

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• cold atoms
• cold molecules
• ultracold atoms
• many-body quantum physics
• precision measurements

Title: Quantum test of the equivalence principle with cold atoms
Authors: Liang Yuan, Sheng-Jun Yang
Affiliation: Shenzhen Institute for Quantum Science and Engineering, School of Science, Southern University of Science and Technology, Shenzhen 518055, China
Abstract: For a hundred years, general relativity is the best theory to describe the gravity and space-time, and successfully explain many physical phenomena. Meanwhile, quantum mechanics provides the most accurate description of the microscopic world, and quantum science technology has evoked broad development today. All the candidate theories that want to unify gravity and quantum mechanics predict the breaking of the equivalence principle, i.e. the heart of general relativity. Thus, it is imperative to carry out experimental verification of the equivalence principle when matter exists significant quantum effects. Cold atoms provide as the test masses having well-defined properties and potential nonlocal correlations, and also will improve the limits reached by classical tests with macroscopic bodies. Stringent test results using cold atoms may tell us whether and how to reformulate the equivalence principle to a quantum version. In this paper, we review the principle and development of test of the equivalence principle with cold atoms. The status and key technologies involved in experiments are discussed in details. In addition, we prospect new questions and opportunities of this topic for further exploration.