Cosmic Bell Experiments: Using Quasars to Test Quantum Theory

UBC Physics & Astronomy Department Colloquium on April 22, 2021. Presented by David Kaiser (MIT). https://phas.ubc.ca/cosmic-bell-exper... Abstract: For decades, physicists have conducted experimental tests of quantum entanglement, a phenomenon that Albert Einstein once dismissed as "spooky action at a distance." Despite Einstein's misgivings, the experiments have consistently found results compatible with quantum theory; today entanglement is at the heart of next-generation devices like quantum computers and quantum encryption. Yet every experimental test has been subject to one or more "loopholes," which (in principle) could account for the results even in the absence of genuine quantum entanglement. This talk describes the latest experimental tests of quantum entanglement, including my group's recent "Cosmic Bell" experiments that used real-time astronomical measurements of light from high-redshift quasars to address the most stubborn of the remaining loopholes. Our experiments provided compelling evidence that quantum entanglement is a robust feature of our world while constraining certain classes of alternative models more thoroughly than ever before. Bio: David Kaiser is Germeshausen Professor of the History of Science and Professor of Physics at the Massachusetts Institute of Technology, where he also serves as Associate Dean for Social and Ethical Responsibilities of Computing. He is the author of several award-winning books about modern physics. His latest book, "Quantum Legacies: Dispatches from an Uncertain World" (2020), was honored as among the best books of the year by "Physics Today" and "Physics World" magazines. A Fellow of the American Physical Society, Kaiser has received MIT's highest awards for excellence in teaching. His work has been featured in "Science", "Nature", the "New York Times", and the "New Yorker" magazine. His group's recent efforts to conduct a "Cosmic Bell" test of quantum entanglement were featured in a documentary film, "Einstein's Quantum Riddle", which premiered in 2019.