Physicists Albert Einstein, Boris Podolsky, and Nathan Rosen proposed the Einstein-Podolsky-Rosen (EPR) Paradox mental experiment in 1935 to highlight that quantum mechanics do not fully explain physical reality. They suggested that quantum theory does not include “elements of reality,” proposing the ability to build a theory that involves hidden variables.
According to the experiment, two dormant particles may have specific physical quantity values, like position or impulse. Even if unmeasured, if one of the particle’s values gets measured, the result could be precisely predicted in the other particle, irrespective of the distance between them. This violates the principle of locality, which states that action on one particle cannot instantly affect the other.
Several physicists conducted different experiments to test the paradox and its implications related to interpreting quantum mechanics. However, none of them could adequately isolate the particles from external influences and control their conditions.
Nevertheless, a team of scientists from China and the United States recently achieved the most comprehensive and accurate EPR paradox test to-date using the Micius satellite launched by China in 2016 to experiment on quantum communication and cryptography. Using a satellite, they produced pairs of photons and transmitted them to two ground stations located more than 1,000 kilometers apart. Then, they calculated the photons’ polarization and compared the results.
Based on the test, the correlation between the photon polarization exceeded what classical probability theory predicted. This confirms the existence of quantum entanglement, refuting the local hidden theory. Hence, they validated the quantum mechanics and countered Einstein, Podolsky, and Rosen’s argument.
The experiment is a significant advancement towards comprehending quantum mechanics’ fundamental nature and how it could be applied to quantum technologies such as quantum communication, quantum calculation, and quantum metrology. The study is published in Physical Review X.