Abstract
The fundamentals of quantum mechanics that we met in Unit 5 characteristically appear on microscopic scales. Macroscopic quantum systems in which liquids, or electric currents, flow without friction or resistance have been known since the early part of the previous century: these are the superfluids and superconductors of traditional condensed matter physics that are discussed in Unit 8. In this unit we focus on an entirely new state of matter only recently created in the laboratory: this is the gaseous macroscopic quantum mechanical system known as a Bose-Einstein Condensate, or BEC. These quantum gases show the full panoply of quantum wave behavior as the individual particles of Unit 5, but now on a size scale visible to the naked eye because many millions, to many billions, of atoms occupy exactly the same quantum state, and thus form a coherent quantum whole. The quantum nature of a BEC can be directly visualized as the quantum effects are not hidden within liquids or solids as is the case with the more traditional superfluids and superconductors. Rather, they may be actually photographed, as the gas itself is a naked macroscopic quantum system. This unit starts by introducing the basic principles necessary to understand BECs, then details how the cooling and trapping introduced in Unit 5 led to the creation and subsequent manipulation of these quantum gases. Finally, we will see how atomic gases of ultra-cold fermions have evolved, in direct analogy to the Cooper paring needed to form bosonic pairs of electrons in superconductors, to molecular BECs, formed from pairs of the fermionic atoms.
About the series:
Explore the frontiers of physics research with the scientists on the front lines in this 11-unit course in modern physics for high school physics teachers, undergraduate students, and science enthusiasts.
Dark matter, string theory, particle accelerators, and other big topics in modern physics come together in this 11-part multimedia course for high school physics teachers, undergraduate students, and all adults who are fascinated by physics and cosmology. The course covers a broad scale, from sub-atomic particle physics, through atomic and molecular physics, to cosmology. The 11 video programs feature 22 case studies of researchers from leading research labs and universities who are breaking new ground in their fields. An extensive companion Web site provides background information and concepts found in a printable online textbook, interactive simulations, a course facilitator's guide, and multiple other resources.
Produced by the Harvard-Smithsonian Center for Astrophysics Science Media Group in association with the Harvard University Department of Physics. 2010.