Quantum tunnelling: Forbidden fruit

Quantum tunnelling is a process by which quantum particles penetrate barriers, usually energy barriers, that are insurmountable to classical objects. In the 1980s physicists predicted the existence of 'dynamical' tunnelling, a quantum process that is classically forbidden by the conservation of a quantity other than the total energy of the system. Now the predictions have borne fruit with the observation of dynamical tunnelling in the ultra-cold atoms of a Bose-Einstein condensate. This opens up new opportunities for the study of nonlinear and classically chaotic systems in the quantum realm, and is also relevant to the study of quantum information.

Dynamical tunnelling of ultracold atoms
W. K. HENSINGER, H. H�FFNER, A. BROWAEYS, N. R. HECKENBERG, K. HELMERSON, C. MCKENZIE, G. J. MILBURN, W. D. PHILLIPS, S. L. ROLSTON, H. RUBINSZTEIN-DUNLOP & B. UPCROFT
Nature 412, 52-55 (5 July 2001)
| First Paragraph | Full Text | PDF (294 K) |

Quantum physics: Air juggling and other tricks
ERIC J. HELLER
Quantum tunnelling breaks the rules of classical physics — and leads to ghost-like transfer of matter through barriers. Demonstrations of a new type of quantum tunnelling have the ghosts taking new liberties.
Nature 412, 33-34 (5 July 2001)
| Full Text | PDF (228 K) |

5 July 2001 table of contents