Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > A New Design for a Gravimeter

Abstract:
Scientists have developed a novel design for a highly compact, ultra-sensitive quantum device to measure subtle changes in gravity over very short time or distance scales.*

A New Design for a Gravimeter

College Park, MD | Posted on September 1st, 2010

Tools of this sort - called atom interferometers (AIs) - are now used to search for natural resources beneath the Earth's surface, navigate deep underwater or in the air, and measure Newton's gravitational constant to extraordinary precision. But the new design, by researchers from the Joint Quantum Institute and its Physics Frontier Center, offers the possibility of unprecedented temporal resolution by harnessing the very recently demonstrated ability to create "synthetic" magnetic fields.

"The ability to measure gravity over fine time scales will help in finding oil fields and mineral deposits," says coauthor and JQI Fellow Victor Galitski. "Imagine an aircraft flying over an unexplored area. If heavy element deposits are hidden underneath, the gravimeter will react promptly by showing strong fluctuations in the local gravity field."

Atom interferometers rely on a counterintuitive but central precept of quantum mechanics: Everything, including matter - not just subatomic particles, atoms and molecules, but also macroscopic objects such as Buicks and buildings - has wave properties. Just like waves of light or sound, "matter waves" from different objects can interfere with one another constructively (reinforcement) or destructively (cancellation).

In addition, the new design takes advantage of yet another quantum phenomenon: "superposition," a condition in which objects have multiple values of the same property at the same time - the equivalent, in the classical world, of a ball that is simultaneously completely red and completely blue until someone looks at it. Once it is seen (or measured in any other way), however, the superposition disappears and the ball becomes either red or blue.

Conventional AIs exploit interference to measure gravity at a given location, typically by directing a stream of atoms into a beamsplitter, which divides the atoms' wave functions into two branches. Inside the device, each branch is propelled on separate - but completely symmetrical, mirror-image - paths down a cylinder. The only difference between the paths is that one is higher than the other - and therefore responds just slightly differently to the force of gravity. So when the two atom branches are recombined, their matter waves will be out of phase; and the amount of phase difference will be proportional to the difference in gravitational force felt by each.

Although useful, that method does not provide a good way to measure how gravitational force changes over small time periods and short length scales. And it necessarily requires the atoms to travel a relatively large distance, typically tens of centimeters, in order to produce a sufficiently large phase difference.

The JQI/PFC design, by contrast, uses an atom trap only 50 micrometers in diameter - about half the thickness of a human hair - containing millions of atoms chilled to a fraction of a degree above absolute zero. The atoms sit in a weak, inhomogeneous magnetic field, and each has a slightly different spin state (a kind of angular momentum) depending on its position in the field. The atoms are irradiated by a continuous-wave laser that imparts momentum to each atom, the magnitude and direction of which depends on the atom's spin state. This arrangement produces "synthetic" magnetism,** a condition which causes neutral atoms to behave as if they were charged particles in a real magnetic field.

"Recently, JQI researchers led by Ian Spielman have demonstrated that a synthetic magnetic field and synthetic spin can be created in cold-atom systems," says coauthor and JQI Fellow Jacob Taylor of the National Institute of Standards and Technology. "The proposed gravimeter setup is largely inspired by these amazing advances, and it uses the simplest possible configuration of replicas of a uniform synthetic field, which can be created easily in Spielman's experiment."

Then each atom is exposed to microwave radiation tuned to the specific wavelength that will project it into a "superposition" of two opposite spin states. [See Step 1 in the attached figure.] At that point, the trap is displaced by a small amount, about 20 micrometers, which has the effect of moving the atom, with its superposed states, into a different part of the synthetic field. [Step 2 in the figure.] Each of the two spin states starts to move in a spiral motion, but in opposite directions around the interior of the trap. [Step 3 in the illustration, also depicted in the short movie.] While in transit, each superposition state will be affected differently by gravity or any other acceleration. As a result, when their paths once again overlap at the end of their spiral trajectories, they will be slightly out of phase.

Finally, the atom is irradiated with a second microwave pulse [Step 4] that causes the atom to emit light if it is in a certain spin state, and to remain "dark" (no emission) if it is in another. If the superposed spin states had not experienced any external effects, such as gravity, each atom in the trap would have a 50-percent chance of emitting or not emitting. But if the paths of the spin states are affected by gravity, the collective output of the entire set of trapped atoms will emit more or less light - and the degree to which the light output varies is a measure of the strength of the gravitational field.

In addition to its potential practical uses, the new design can help test the fundamental laws of nature, such as Einstein's theory of relativity, which some believe maybreak down at very small time and length scales.

* "Interferometry with Synthetic Gauge Fields," B. M. Anderson, J. M. Taylor, and V. M. Galitski, arxiv.org/abs/1008.3910

** "Synthetic magnetic fields for ultracold neutral atoms," Y.-J. Lin, R.L. Compton, K. Jimenez-Garcia, J.V. Porto and I.B. Spielman, Nature 462, 628 (2009).

####

About Joint Quantum Institute
We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

For more information, please click here

Contacts:

Copyright © Joint Quantum Institute

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Aculon Hires New Business Development Director December 19th, 2014

Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014

Physics

SUNY Poly NanoCollege Faculty Member Selected as American Physical Society Fellow: SUNY Poly Associate Professor of Nanoscience Dr. Vincent LaBella Recognized for Significant Technological Innovations that Enable Interactive Learning December 17th, 2014

Fraud-proof credit card possible because of quantum physics December 16th, 2014

Nanoscale resistors for quantum devices: The electrical characteristics of new thin-film chromium oxide resistors that can be tuned by controlling the oxygen content detailed in the 'Journal of Applied Physics' December 9th, 2014

Unusual Electronic State Found in New Class of Unconventional Superconductors: Finding gives scientists a new group of materials to explore to unlock secrets of some materials' ability to carry current with no energy loss December 8th, 2014

Possible Futures

A novel method for identifying the body’s ‘noisiest’ networks November 19th, 2014

Researchers discern the shapes of high-order Brownian motions November 17th, 2014

VDMA Electronics Production Equipment: Growth track for 2014 and 2015 confirmed: Business climate survey shows robust industry sector November 14th, 2014

Open Materials Development Will Be Key for HP's Success in 3D Printing: HP can make a big splash in 3D printing, but it needs to shore up technology claims and avoid the temptation of the razor/razor blade business model in order to flourish November 11th, 2014

Academic/Education

SUNY Poly NanoCollege Faculty Member Selected as American Physical Society Fellow: SUNY Poly Associate Professor of Nanoscience Dr. Vincent LaBella Recognized for Significant Technological Innovations that Enable Interactive Learning December 17th, 2014

Nanomedicine expert joins Rice faculty: Gang Bao combines genetic, nano and imaging techniques to fight disease December 17th, 2014

FEI and Oregon Health & Science University Install a Complete Correlative Microscopy Workflow in Newly Built Collaborative Science Facility December 16th, 2014

Student Nanotechnology Laboratories Network Set Up in Iran December 15th, 2014

Announcements

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Aculon Hires New Business Development Director December 19th, 2014

Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014

Quantum nanoscience

Fraud-proof credit card possible because of quantum physics December 16th, 2014

Nanoscale resistors for quantum devices: The electrical characteristics of new thin-film chromium oxide resistors that can be tuned by controlling the oxygen content detailed in the 'Journal of Applied Physics' December 9th, 2014

High photosensitivity 2D-few-layered molybdenum diselenide phototransistors December 8th, 2014

Electron pairs on demand: Controlled emission and spatial splitting of electron pairs demonstrated December 4th, 2014

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE