Testing the limits of quantum mechanics: motivation, state of play, prospects

About:

  I present the motivation for experiments which attempt to generate, and verify the existence of, quantum superpositions of two or more states which are by some reasonable criterion "macroscopically" distinct, and show that various a priori objections to this program made in the literature are flawed. I review the extent to which such experiments currently exist in the areas of free-space molecular diffraction, magnetic biomolecules, quantum optics and Josephson devices, and sketch possible future lines of development of the program.

Short Biography

Professor Anthony J. Leggett, a faculty member of the University of Illinois at Urbana-Champaign since 1983, is widely recognized as a world leader in the theory of low-temperature physics. He was awarded the Nobel Prize in Physics in 2003 (jointly with Alexei A. Abrikosov and Vitaly L. Ginzburg) for his pioneering work on superfluidity.

Anthony Leggett has shaped the theoretical understanding of normal and superfluid helium liquids and other strongly coupled superfluids. He set directions for research in the quantum physics of macroscopic dissipative systems and use of condensed systems to test the foundations of quantum mechanics. His research interests lie mainly within the fields of theoretical condensed matter physics and the foundations of quantum mechanics. He has been particularly interested in the possibility of using special condensed-matter systems, such as Josephson devices, to test the validity of the extrapolation of the quantum formalism to the macroscopic level; this interest has led to a considerable amount of technical work on the application of quantum mechanics to collective variables and in particular on ways of incorporating dissipation into the calculations. He is also interested in the theory of superfluid liquid 3He, especially under extreme nonequilibrium conditions, in high-temperature superconductivity, and in the newly realized system of Bose-condensed atomic gases.