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发布者： admin 发布时间：2010-06-18

　　

Perspectives

Physics:

A Drop of Quantum Matter

Paulo Nussenzveig and João C. A. Barata

Physics in the 20th century witnessed two major revolutions, relativity and quantum mechanics. General relativity relies on the equivalence principle. When an object in a gravitational field undergoes free fall, it is indistinguishable from the same object in an inertial reference frame—it acts as if it were weightless in outer space. A popular account of a free-fall environment was given by the thought experiment of "Einstein's elevator" (1) (see the figure, panel A). General relativity is mainly formulated in terms of classical objects. On page 1540 of this issue, van Zoest et al. (2) describe an intriguing experiment that brings together fundamentals of general relativity and quantum mechanics. They follow the evolution of a prototypical quantum object, a Bose-Einstein condensate (BEC), under free-fall conditions (see the figure, panel B). The use of BECs in atom interferometers should allow for more sophisticated tests of general relativity.

Instituto de Física, Universidade de São Paulo, Post Office Box 66318, São Paulo, SP 05314-970, Brazil.

Reports

Bose-Einstein Condensation in Microgravity

T. van Zoest,¹ N. Gaaloul,¹ Y. Singh,¹ H. Ahlers,¹ W. Herr,¹ S. T. Seidel,¹ W. Ertmer,¹ E. Rasel,^1,* M. Eckart,² E. Kajari,² S. Arnold,² G. Nandi,² W. P. Schleich,² R. Walser,³ A. Vogel,⁴ K. Sengstock,⁴ K. Bongs,⁵ W. Lewoczko-Adamczyk,⁶ M. Schiemangk,⁶ T. Schuldt,⁶ A. Peters,⁶ T. Könemann,⁷ H. Müntinga,⁷ C. Lämmerzahl,⁷ H. Dittus,⁷ T. Steinmetz,⁸ T. W. Hänsch,⁸ J. Reichel⁹

 

Albert Einstein’s insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.