The density of Bose-Einstein condensates, exhibiting interference of their quantum mechanical wave functions. From https://sites.google.com/site/bigelowcatgroup/bec.
BSU’s Materials Science and Engineering Dept had a guest today from the University of Rochester, Prof. Nick Bigelow. Prof. Bigelow spoke this afternoon in the physics department about his experiments producing Bose-Einstein condensates in his optics lab. He did a great job of explaining their subtle physics at a level that our undergrads and even our lowly astronomers could understand.
In his lab, he uses lasers to cool small pockets of low-density rubidium gas to a Bose-Einstein condensation state and then spins up a torus of the gas with variously polarized laser beams. The quantum mechanical wave function describing the gas torus must then have an integer number of oscillations over its circumference.
By putting the spinning torus of gas into contact with other Bose-Einstein condensates with known wave functions (either spinning or not), Bigelow’s group can demonstrate the effects of interference between the quantum mechanical wave functions for the two condensates. The figure at top left shows the clouds of gas that form, exhibiting graceful density enhancements (warmer colors) that result from interference of the wavefunctions.
As lucid and compelling as Bigelow’s talk was, it highlighted again for me how strange and counter-intuitive quantum mechanical systems are. It reminded me of Richard Feynman‘s famous quote, “If you think you understand quantum mechanics, you don’t understand quantum mechanics” (which, I just learned, is not a Feynman quote at all, but a paraphrase of a Bohr quote).