Measuring and testing – Gravitational determination
Reexamination Certificate
1999-11-12
2001-11-13
Chapman, John E. (Department: 2856)
Measuring and testing
Gravitational determination
Reexamination Certificate
active
06314809
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to measurement of the force of gravity and other forces and, more particularly, to a method of gravity measurement using Bose-Einstein condensed vapors and atom interferometry.
BACKGROUND OF THE INVENTION
In 1995, Anderson et al. in “Observation of Bose-Einstein Condensation in Dilute Atomic Vapor”, Science, Vol. 269, Jul. 14, 1995, pp.198-201, demonstrated that a dilute vapor of
87
Rb could be cooled to the temperature required for observation of Bose-Einstein condensation. Bose-Einstein condensation (BEC) occurs when noninteracting bosonic atoms, below a certain temperature, suddenly develop a macroscopic population in the lowest energy quantum mechanical state of an external confining potential. In such state, the de Broglie wavelength (i.e., Planck's constant divided by the product of mass and the velocity of the speed of light) associated with an atomic wave packet becomes comparable with or larger than the spacing between particles in the gas.
Atoms in this state have coherence properties which are similar to those of optical lasers. Wolfgang Ketterle's group at MIT (i.e., see “Observation of Interference Between Two Bose Condensates”, Andrews et al., Science, Vol. 275, Jan. 31, 1997, pp. 637-641), reported observation of interference from two independent Bose condensates. Ketterle's group produced two independent condensates and released the condensates from traps used to create two expanding clouds of atoms—one cloud from one condensate, the other cloud from the other condensate—which eventually overlapped. By taking a picture of the atoms in the overlap region, they observed interference fringes which they interpreted as interference of de Broglie waves originating with each of the two condensates. This was the first demonstration of the phase coherence properties of a BEC and indicated that the output of each condensate was essentially a coherent beam of atoms.
Currently, a number of methods are used to measure the force of gravity and other weak forces. Especially in geological exploration, there exists a need for more highly accurate gravity measurements to provide indications of buried mineral and oil deposits.
Accordingly, it is an object of this invention to provide an improved method for the measurement of weak forces.
It is another object of this invention to provide a method for the measurement of the force of gravity that manifests atomic level measurement accuracies.
SUMMARY OF THE INVENTION
The invention uses coherent outputs from two or more Bose-Einstein condensates (BECs) to characterize the acceleration due to gravity. The condensates are created at two or more different heights in the gravitational potential. de Broglie waves are extracted from each of these condensates and are interfered at a detector which is located below the lower condensate. In the same manner as an optical heterodyne experiment, interference of the two “atom laser beams” results in a beatnote whose frequency is given by the energy difference associated with each atom laser beam. This beat frequency is given by the frequency difference of the two atom laser beams and is proportional (via Planck's constant) to the energy difference of the interfering beams. This energy difference allows the force of gravity to be derived at a level of sensitivity approaching 10
−14
g (where g is the acceleration due to gravity).
REFERENCES:
patent: 3761721 (1973-09-01), Altshuler et al.
patent: 4874942 (1989-10-01), Clauser
“Output Coupler for Bose-Einstein Condensed Atoms” Mewes et al., Phys. Rev. Letters, V78, No. 4, Jan. 27, 1997, pp. 582-585.
“Bloch Oscillations of Atoms in an Optical Potential”, BenDahan et al., Phys. Rev. Letters, V76, No. 24, Jun. 10, 1996 pp. 4508-4511.
“Observation of Interference Between Two Bose Condensates”, Andrews et al., Science, V275, Jan. 31, 1997, pp. 637-641.
“Observation of Bose-Einstein Condensation in a Dilute Atomic Vapor”, Anderson et al., Science, V269, Jul. 14, 1995, pp. 198-201.
Anderson Brian P.
Kasevich Mark A.
Chapman John E.
Ohlandt Greeley Ruggiero & Perle L.L.P.
Yale University
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