n-EDM Collaboration n-EDM Collaboration Meeting:Meeting:Precision Precision

MagnetometryMagnetometry

Alex Sushkov and Dima Alex Sushkov and Dima Budker Budker

BerkeleyBerkeley UIUC, December 2-3, 2004UIUC, December 2-3, 2004

The Concept

Medium

Linear Polarization

Circular Components

MagneticField

Commercial dense flint glasses: Commercial dense flint glasses: V~3V~31010-5-5 rad/G/cm rad/G/cm

Atomic vapor (very-high vacuum): Atomic vapor (very-high vacuum): V~10V~1044 rad/G/cm rad/G/cm

~10~102020 greater rotation "per atom" greater rotation "per atom"

Cold Atomic Cold Atomic MagnetometerMagnetometer

• Expected B-field from 3He spins:B ~ 2×1012 • 10-20/2000 • 2.1 • 8 ~ 2×10-10 G

• State-of-the-art SQUIDs ~ 3×10-11 G/Hz1/2 at 4 K• Demonstrated warm atomic magnetometers ~ 10-11 G/Hz1/2

• The goal for the cold Ag magnetometer: B-field sensitivity ~ 10-12 G/Hz1/2 or better and operation around 4 K• This corresponds to spin-relaxation time of ~ 30 seconds• Spin-relaxation times around 60 seconds have been indirectly observed [Yabuzaki]

Cold Atomic Cold Atomic MagnetometerMagnetometer

Cold Atomic Cold Atomic MagnetometerMagnetometer

Cold Atomic Cold Atomic MagnetometerMagnetometer

Quantum Non-Demolition Quantum Non-Demolition and Spin-Squeezingand Spin-Squeezing

• How do the noise properties of an atomic magnetometer or an EDM experiment scale with the number N of the species under study?• 1/√N?• Fundamental noise sources for an atomic magnetometer:

• quantum projection noise• photon shot-noise

• For short measurement times (τ « τrel/√N), the optimal sensitivity scales as N-3/4

• But at longer measurement times (τ ~ τrel) the optimal sensitivity scales as 1/√N, as for a usual shot-noise limited system• If strongly squeezed probe light is used, the Heisenberg limit may, in principle, be reached for very short measurement times, but once again the 1/√N scaling is restored for τ ~ τrel

M. Auzinsh, D. Budker D. F. Kimball, S. M. Rochester, J. E. Stalnaker,

A. O. Sushkov, and V. V. Yashchuk, Phys. Rev. Lett. 93(17), 173002 (2004); physics/0403097 .