Scaling up the precision in BEC Contrast Interferometry
We are working on a Yb BEC based contrast interferomter with a major goal of measuring the fine structure constant and thus testing QED at high precision
(details of earlier work can be found in [1]). We have recently reached a new milestone in this project. This is summarized
in the preliminary data presented in the figure. The upper panel shows the phase evolution vs interferometer time and demonstrates a phase evolution rate which is quadratic with momentum separation between interferometer
paths. The slope of each fitted line grows as N^2. The two outer paths of the 3path interferometer are separated by 4*N recoil momenta. Thus N=13 corresponds
to 52 recoil momentum separation. The phase stability of the interferometer is shown in the lower panel. The standard deviation of the interferometer phase
is small, remaining less than 200mrad even for 52 recoil momentum separation (N=13). This scaledup interferometer is already more than 100 times as sensitive
as our earlier one [1] and further scaling up with higher N seems feasible. We want to make a measurement well below 1 ppb for the fine structure constant and
thus test QED theory at high precision.
References:
[1] A.O. Jamison, B. PlotkinSwing, and S. Gupta, Advances in precision contrast
interferometry with Yb BoseEinstein condensates, Phys. Rev. A. 90, 063606 (2014).

