John Clauser

University of California, Berkeley

John Francis Clauser is an American physicist whose experimental work on quantum entanglement laid the foundation for quantum information science. In 1972, working at UC Berkeley, he performed the first experimental test of Bell's inequalities together with Stuart Freedman. Their results confirmed that quantum mechanics violates Bell inequalities — demonstrating that nature is fundamentally nonlocal and ruling out a large class of hidden-variable theories. Clauser's methodology, later refined by Alain Aspect and Anton Zeilinger, formed the basis for the entire field of experimental quantum optics and quantum cryptography. He shared the 2022 Nobel Prize in Physics with Aspect and Zeilinger for these experiments establishing the reality of quantum entanglement. Quantum entanglement is now the central resource in quantum computing, quantum cryptography, and quantum teleportation — multibillion-dollar research areas that Clauser's foundational experiments made possible.