Magnetics Business & Technology - Spring 2014 - (Page 22)
RESEARCH & DEVELOPMENT
JILA Team Develops 'Spinning Trap' to Measure Electron Roundness
Artist's conception of JILA's new technique for measuring the electron's roundness, or electric dipole moment (EDM). The method involves
trapping molecular ions of hafnium fluoride (red and blue spheres, respectively) in spinning electric and magnetic fields. Researchers measure
changes over time in the "spin" direction of the molecules' unpaired electrons (arrows in yellow spheres), which act like tiny bar magnets. Specific patterns in the rate of change, reflecting alterations in the gap between two magnetic energy levels in the molecules, would indicate the
existence and size of an EDM. Credit: Baxley/JILA
JILA researchers have developed a method of spinning electric
and magnetic fields around trapped molecular ions to measure
whether the ions' tiny electrons are truly round, research with major implications for future scientific understanding of the universe.
JILA Spin Trap to measure electron EDM.
The JILA team used their new spinning method to make their
first measurement of the electron's roundness, technically, the
electron's electric dipole moment (eEDM), a measure of the uniformity of the electron's charge between its poles. The JILA team's
measurement is not yet as precise as eEDM measurements made
by other groups. But the main purpose of the research at this time
is to demonstrate a powerful new technique that may eventually
provide the best eEDM measurements, and may also be useful in
quantum information and simulation experiments.
JILA is a joint institute of the National Institute of Standards and
Technology (NIST) and the University of Colorado Boulder.
JILA/NIST Fellow Eric Cornell says his quest to measure the eEDM,
five years and counting, is as challenging as looking for a single virus
particle on an object the size of Earth.
"Our paper presents a new method for getting to a better limit
on the electron's electric dipole moment," Cornell says. "Our hope
is eventually to leapfrog over existing limits and get a still better
result, but that will be at least a couple years out."
Decades ago, physicists believed the electron was perfectly
round. In the 1980s, the idea of a slight asymmetry became acceptable, but any eEDM was thought to be too tiny to see. Some current
theories predict that the eEDM might be only a bit smaller than the
latest measurements indicate and might arise from exotic, as-yetunknown particles.
Magnetics Business & Technology * Spring 2014
Scientists are now trying to push the limits of eEDM measurements to either validate or disapprove some of the competing theories. The current experimental upper limit is much, much larger
than the eEDM predicted by the Standard Model of physics. But
extensions to this model such as supersymmetry predict a value
close to the experimental limits. By making more precise measurements, scientists hope to test these new theories.
Scientists try to measure the speedy electron's properties by attaching it to a bigger object, like a molecule. The JILA team focused
on electrons associated with hafnium fluoride ions, so-called polar
molecules with a positive charge at one end and a negative charge
at the other end. Polar molecules can be trapped and manipulated
with electric fields to remain in target states for 100 milliseconds,
long enough for a precision measurement. The electric field inside
the molecules is used to amplify the potential signal of eEDM.
JILA's method involves rotating electric and magnetic fields fast
enough to trap the molecular ions but slowly enough for the ions
to be aligned with the electric field. The ions rotate in individual
micro-circles while scientists measure their properties. The EDM is
the difference between two magnetic energy levels. The method
was developed in a collaboration between Cornell and JILA/NIST
Fellow Jun Ye, who has conducted research with polar molecules.
The rotating field technique may be useful in quantum information experiments because a quantum bit could hold information for
longer time periods in its electric and magnetic energy levels than
in more commonly used quantum states. The ability to manipulate
interactions of molecular ions might also simplify simulations of
other spin-based quantum systems. In addition, the new technique
might be used to investigate any variations over time in the fundamental "constants" of nature used in scientific calculations.
Table of Contents for the Digital Edition of Magnetics Business & Technology - Spring 2014
Magnetic Design and Applications Using Halbach Theory
Test & Measurement
Optimizing Magnetic Core Gapping for Low-Loss Sine-Wave Inductors
White Paper: Toroidal Line Power Transformers
Magnetics, Materials & Assemblies
Research & Development
Software & Design
Marketplace / Advertising Index
Spontaneous Thoughts: NdFeB: It's About the Cerium
Magnetics Business & Technology - Spring 2014