An improved measurement of the electron electric dipole moment using YbF molecules.

Lead Research Organisation: Imperial College London
Department Name: Dept of Physics

Abstract

We have developed a method to measure the shape of the electron by carefully studying how it behaves when it is placed in an electric field. Each electron that we study is part of a molecule (ytterbium fluoride), which amplifies the applied electric field and also serves as an anchor so that the electron is not swept away by the field. We use lasers and radiofrequency fields to prepare the electron's spin in a particular direction. The electric field causes this spin direction to rotate by an amount that depends on the electron's shape, and we measure this angle of rotation. We have recently made the most sensitive measurement of the electron's shape and we now plan to exploit our method to improve the precision of the measurement by a factor of 20.

This atomic physics experiment will provide important new information about the fundamental laws of physics that describe sub-atomic particles. We also hope to shed some light on one of the biggest mysteries in physics: why there is so much more matter than antimatter in the universe.

The best theory of particle physics at the moment, the Standard Model, predicts the behaviour of sub-atomic particles with amazing accuracy, but it is obviously incomplete. For instance, it doesn't include the effects of gravity, it can't explain why the different forces of nature have such widely differing strengths, and it can't reproduce the observed matter/antimatter asymmetry. Physicists have proposed many ideas to extend the Standard Model, but we don't know which, if any, of these proposed theories is the right one.

Our measurement of the electron's shape can help sort this out, because the different proposed theories predict different shapes. By increasing the accuracy of our measurement, we can test these theories. One of the favourite theoretical ideas is called supersymmetry. Our recent measurement has already ruled out some versions of this theory. With the planned improvement, our new measurement will either rule out most versions of supersymmetry, or will provide some evidence that supersymmetry is correct.

Physicists think that the universe started with the big bang, which should have created equal amounts of matter and antimatter, yet today we only see tiny amounts of antimatter, coming from unusual things like cosmic rays and radioactive decay. This is a puzzle because it implies an asymmetry between the laws governing matter and antimatter that is not in the Standard Model. Our measurement is relevant because the shape of the electron is extremely sensitive to such an asymmetry. Even a tiny difference would distort the shape significantly, so our measurement may help to solve this mystery about the evolution of the early universe.

Planned Impact

WHO WILL BENEFIT FROM THIS RESEARCH?
A. Academic beneficiaries (see "academic beneficiaries" section)

B. Commercial beneficiaries. It is likely that future commercial devices based on the quantum control of molecules will benefit from this research.

C. General Public.

HOW WILL THEY BENEFIT?
A. The academics will benefit from understanding more deeply how the laws of physics operate at energies above 1TeV and how they affect the evolution of the early universe through the matter/antimatter asymmetry. Those using molecules for metrology and high-precision studies will benefit from our learning how to make more intense molecular sources and how to control them better. Chemists seeking improved control and understanding of elementary reactions can also benefit from our source development and from our understanding of quantum coherence and control over single quantum levels.

B. It is likely that future devices will be based on quantum control of cold molecules. Molecular clocks are one obvious example. Even though these may not use the particular molecular species that we use here, the techniques that we develop and the physicists whom we train will provide valuable input for the future needs of industry in this area of molecular quantum devices.

C. The general public will benefit from our efforts to explain what we are doing and why. Many people are intrigued and excited by tabletop experiments such as this, which answer deep scientific questions. Public engagement of this sort encourages political support for science and that in turn generates a society with scientific competence.

Publications

10 25 50
publication icon
Bulleid NE (2013) Characterization of a cryogenic beam source for atoms and molecules. in Physical chemistry chemical physics : PCCP

publication icon
Hudson J (2014) Stochastic multi-channel lock-in detection in New Journal of Physics

publication icon
Rabey IM (2016) Low magnetic Johnson noise electric field plates for precision measurement. in The Review of scientific instruments

publication icon
Sauer B (2013) Time reversal symmetry violation in the YbF molecule in Hyperfine Interactions

publication icon
Sauer B (2017) A big measurement of a small moment in New Journal of Physics

 
Description We have developed a major new technique for optical/microwave/rf pumping in a very complex manifold of molecular states and have applied this technique to build a new instrument of world-leading sensitivity in searching for the electron EDM. This work also has direct application to the future possibility of laser cooling molecules.
Exploitation Route It is likely that future devices will be based on quantum control of cold molecules. Molecular clocks are one obvious example. Even though these may not use the particular molecular species that we used here, the techniques that we developed and the physicists whom we trained will provide valuable input for the future needs of industry in this area of
molecular quantum devices.
Sectors Digital/Communication/Information Technologies (including Software),Education,Energy

 
Description Our findings have been used to make an improved measurement of the electron's permanent electric dipole moment.
First Year Of Impact 2011
Sector Education
Impact Types Cultural

 
Description ERC Advanced Grants
Amount £1,853,561 (GBP)
Funding ID 320789 
Organisation European Research Council (ERC) 
Sector Public
Country European Union (EU)
Start 02/2013 
End 01/2018
 
Description PPRP 2018
Amount £1,263,790 (GBP)
Funding ID ST/S000011/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 10/2018 
End 09/2022
 
Description Particle Physics Consolidated Grant - Measurement of the eEDM
Amount £724,632 (GBP)
Funding ID ST/N000242/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 10/2015 
End 09/2019
 
Description Research Grant - Measurement of the electron edm: eEDM (CG)
Amount £83,183 (GBP)
Funding ID ST/K001604/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 10/2012 
End 09/2016
 
Description Revealing the undiscovered forces that break matter-antimatter symmetry by measuring the shape of electrons (Templeton)
Amount £888,745 (GBP)
Funding ID 61104 
Organisation The John Templeton Foundation 
Sector Academic/University
Country United States
Start 10/2018 
End 06/2021
 
Description The study of elementary particles and their interactions (Consolidated Grant 2019 - 2022)
Amount £14,105,169 (GBP)
Funding ID ST/S000739/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 10/2019 
End 09/2022
 
Description Prof. Tim Steimle, Arizona State University 
Organisation Arizona State University
Department School of Molecular Sciences
Country United States 
Sector Academic/University 
PI Contribution xxx
Collaborator Contribution xxx
Impact 1. X. Zhuang, A. Le, T. C. Steimle, N.E. Bulleid, I. J. Smallman, R.J. Hendricks, S.M. Skoff, J. J. Hudson, B. E. Sauer, E. A. Hinds and M. R. Tarbutt, "Franck-Condon factors and radiative lifetime of the A2P1/2-X2S+ transition of ytterbium monofluoride, YbF", Phys. Chem. Chem. Phys. 13 19013 (2011). DOI: 10.1039/c1cp21585j 2. Smallman IJ, Wang F, Steimle TC, Tarbutt MR, Hinds EA "Radiative branching ratios for excited states of (YbF)-Yb-174: Application to laser cooling" JMS 300:3-6 01 Jun 2014 doi: 10.1016/j.jms.2014.02.006 3. M.R. Tarbutt and T.C. Steimle, "Modeling magneto-optical trapping of CaF molecules", Phys. Rev. A 92, 053401 (2015) DOI:10.1103/PhysRevA.92.053401
Start Year 2010
 
Description BBC Science programme - From Ice to Fire: The Incredible Science of Temperature 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact An interview was filmed in our lab as part of BBC science programme - Title, From Ice To Fire - The Incredible Science Of Temperature, in which scientist Helen Czerski explores the physics and dynamics at the heart of the subject. In episode one, Helen ventures to the bottom of the temperature scale, revealing how cold has shaped the world around us and why frozen doesn't mean what you might think. She meets the scientists pushing temperature to the very limits of cold, where the normal laws of physics break down and a new world of scientific possibility begins. The extraordinary behaviour of matter at temperatures close to absolute zero is driving the advance of technology, from superconductors to quantum computing.
Year(s) Of Engagement Activity 2018
URL https://www.bbc.co.uk/iplayer/episode/b09rzqp3/from-ice-to-fire-the-incredible-science-of-temperatur...