First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers.
Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of colocated 39 m long, high power Michelson interferometers with flat broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light-crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2×10^{8} independent spectral measurements with 381 Hz frequency resolution to obtain 2.1×10^{-20}m/sqrt[Hz] sensitivity to stationary signals. For signal bandwidths Δf>11  kHz, the sensitivity to strain h or shear power spectral density of classical or exotic origin surpasses a milestone PSD_{δh}<t_{p} where t_{p}=5.39×10^{-44}/Hz is the Planck time.
Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.
Aaron S
AS
Chou
University of Michigan, Ann Arbor, Michigan 48109, USA.
Richard
R
Gustafson
Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.|University of Chicago, Chicago, Illinois 60637, USA.
Craig
C
Hogan
University of Chicago, Chicago, Illinois 60637, USA.|Vanderbilt University, Nashville, Tennessee 37235, USA.
Brittany
B
Kamai
University of Chicago, Chicago, Illinois 60637, USA.|Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
Ohkyung
O
Kwon
University of Chicago, Chicago, Illinois 60637, USA.|Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA.
Robert
R
Lanza
University of Chicago, Chicago, Illinois 60637, USA.|Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA.
Lee
L
McCuller
University of Chicago, Chicago, Illinois 60637, USA.
Stephan S
SS
Meyer
University of Chicago, Chicago, Illinois 60637, USA.
Jonathan
J
Richardson
Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.
Chris
C
Stoughton
Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.
Raymond
R
Tomlin
SpaceX, Hawthorne, California 90250, USA.
Samuel
S
Waldman
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA.
Rainer
R
Weiss