Rotation, acceleration, and gravity sensors using quantum-mechanical matter-wave interferometry with neutral atoms and molecules
First Claim
1. Apparatus for measuring the spatial gradient of a gravitational field, comprisinga means for producing neutral particles selected from atoms and molecules,an interferometer, including propagation path defining means, in which the particles and their associated matter waves propagate along a plurality of positionally separated paths, with a geometry in which the paths are positionally separated from each other and have a negligible average lateral positional displacement from each other, wherein the paths circuit about opposite sides of two approximately equal adjacent areas in a figure-eight configuration, with each path circuiting in an opposite sense about each of the two areas, and a region where the quantum-mechanical matter-waves associated with the particles interfere,a means for detecting the interference between the matter waves,a means for providing some isolation between the interferometer and the vibrations of its environment.
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Abstract
The invention is a neutral atom (and/or molecule) matter-wave interferometer (and/or set of interferometers) that can be used as an inertial sensor with a sensitivity exceeding that of conventional mechanical sensors and multiple circuit optical interferometers (including ring lasers) by many powers of ten. An interferometer in which matter-wave propagation beam paths enclose a finite area will sense rotations via the Sagnac effect. One with the paths displaced from each other will sense acceleration plus gravity. Interferometers with paths that follow a figure-eight pattern yield a gravitational gradiometer. Laser cooling and slowing of a beam of neutral atoms provides a low energy nearly monochromatic source. Diffraction gratings are employed as beam splitters. Such gratings may consist of apertures in a sheet of solid material, near-resonant standing-wave laser beams, or crystal faces. Path curvature due to acceleration and rotation is canceled by magnetic and/or electric field gradients that produce an effective levitation of slow atoms. A feedback system that maintains an interferometer phase null is employed with its error signal yielding the inertial effect signals. Magnetic and/or electric fields are used for producing matter-wave phase shifts. The invention may be used to measure acceleration, rotation, position, orientation, gravity, the mass distribution of nearby matter, and an electric current. Other important applications are mass tomography, geodesy, and petroleum exploration.
87 Citations
51 Claims
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1. Apparatus for measuring the spatial gradient of a gravitational field, comprising
a means for producing neutral particles selected from atoms and molecules, an interferometer, including propagation path defining means, in which the particles and their associated matter waves propagate along a plurality of positionally separated paths, with a geometry in which the paths are positionally separated from each other and have a negligible average lateral positional displacement from each other, wherein the paths circuit about opposite sides of two approximately equal adjacent areas in a figure-eight configuration, with each path circuiting in an opposite sense about each of the two areas, and a region where the quantum-mechanical matter-waves associated with the particles interfere, a means for detecting the interference between the matter waves, a means for providing some isolation between the interferometer and the vibrations of its environment.
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2. Apparatus for measuring an electric current, comprising
a means for producing neutral particles selected from atoms and molecules, an interferometer, including propagation path defining means, in which the particles and their associated matter waves propagate along a plurality of positionally separated paths and a region where the quantum-mechanical matter-waves associated with the particles interfere, at least one electric conductor passing near at least one of the propagation paths, carrying a current to be measured, a means for measuring the matter-wave phase shift produced by the electric current'"'"'s magnetic field.
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3. Apparatus for producing neutral particle matter-wave interference, comprising
a source of neutral particles selected from atoms and molecules, means for collimating the neutral particles into a beam, a means for diminishing the spread of velocity vectors among particles issuing from the source, a neutral atom interferometer, further comprising a sequence of spaced, substantially planar solid sheets, each sheet having at least one aperture therethrough positioned so that the particles and their associated matter waves propagate through said apertures, and with the aperture arrangement on at least one of the sheets configured so that there is at least one imaginary straight line segment that passes through a solid portion of that sheet when drawn between two points that both lie within the geometrical plane of that sheet and that both lie inside an aperture of that sheet, a region where the quantum-mechanical matter-waves associated with the particles interfere, means for detecting particles that pass through the slits in the sequence of sheets.
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19. Apparatus for producing neutral particle matter-wave interference, comprising
a source of neutral particles selected from atoms and molecules, means for collimating the neutral particles into a beam, a neutral atom interferometer, further comprising a crystal face that reflectively splits the beam into a plurality of positionally separated coherent beams which propagate along positionally separated paths, at least one crystal face that reflects at least one of the spatially separated beams, a crystal face where the quantum-mechanical matter-waves associated with the particles in the spatially separated beams interfere and reflect, means for detecting particles that have been reflected by the crystal faces.
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23. Method for obtaining information concerning the mass distribution of adjacent matter by measuring the spatial gradient of the gravitational field produced by the matter, comprising
producing a collimated beam of neutral particles selected from atoms and molecules, forming an interferometer by propagating the particles and their associated matter waves along a plurality of positionally separated paths in an interferometer with a geometry in which the paths are positionally separated from each other and have a negligible average lateral positional displacement from each other, by providing paths that circuit about opposite sides of two approximately equal adjacent areas in a figure-eight configuration with each path circuiting in an opposite sense about each of the two areas, locating the interferometer near the matter whose mass distribution is to be measured, detecting the interference of the matter waves in a region where the quantum-mechanical matter-waves associated with the particles interfere,
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30. Method for measuring an electric current, comprising
producing neutral particles selected from atoms and molecules, collimating the particles into a beam, propagating the particles and their associated matter waves along a plurality of positionally separated paths to a region where the quantum-mechanical matter-waves associated with the particles interfere, passing near at least one of the propagation paths an electric current to be measured, measuring the phase shift of the matter waves produced by the magnetic field produced by the electric current.
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31. Method for producing and detecting neutral particle matter-wave interference, comprising
providing a source of neutral particles selected from atoms and molecules, collimating the neutral particles into a beam, diminishing the spread of velocity vectors of particles issuing from the source, providing a neutral atom interferometer, by further aligning a sequence of spaced substantially planar solid sheets, each sheet having at least one aperture therethrough, propagating the particles and their associated matter waves through said apertures, configuring the aperture arrangement on at least one of the sheets so that there is at least one imaginary straight line segment that passes through a solid portion of that sheet when drawn between two points that both lie within the geometrical plane of that sheet and that both lie inside an aperture of that sheet, providing a region where the quantum-mechanical matter-waves associated with the particles interfere, detecting the particles that pass through the apertures in the sequence of sheets.
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48. Method for producing neutral particle matter-wave interference, comprising
providing a source of neutral particles selected from atoms and molecules, collimating the neutral particles into a beam, reflectively splitting the beam into a plurality of positionally separated coherent beams at a crystal face, propagating the plurality of beams along positionally separated paths, reflecting at a crystal face at least one of the positionally separated beams to make it converge with at least one of the other beams, locating a reflecting crystal face in a region where the spatially separated beams converge and interfere, detecting the particles that have been reflected by the crystal faces.
Specification