Three-Path Atom Interferometry with Large Momentum Separation

Abstract

We demonstrate the scale up of a symmetric three-path contrast interferometer to large momentum separation. The observed phase stability at separation of 112 photon recoil momenta exceeds the performance of earlier free-space interferometers. In addition to the symmetric interferometer geometry and Bose-Einstein condensate source, the robust scalability of our approach relies on the suppression of undesired diffraction phases through a careful choice of atom optics parameters. The interferometer phase evolution is quadratic with number of recoils, reaching a rate as high as 7 × 10 7 radians/s. We discuss the applicability of our method towards a new measurement of the fine-structure constant and a test of QED.

Measurement of a Li7 tune-out wavelength by phase-patterned atom interferometry

“…Measurement of TO in metastable helium [38] has also inspired a rich interaction with theory [41,62]. Our tension with theory suggests that an independent measurement of TO in ultracold 6,7 Li [63-71] could add a valuable contribution to the dialogue between theory and experiment.…”

“…In atom interferometers, phase differences between matter waves propagating on separated paths translate into measurable population differences at the output ports [1]. The phase difference is typically uniform across the sample [2][3][4][5][6][7][8][9][10][11][12][13][14][15] or has a constant gradient [16][17][18][19]. Detection methods tend to average out intricate spatial phase patterns that may be introduced during the interferometer.…”

“…Image analysis extracts the resulting population pattern despite a signal-to-noise ratio well below unity for any single image. We implement this technique to measure the tune-out (TO) wavelength of 7 Li near 671 nm, the wavelength where the ground state's polarizability α, or AC Stark shift f AC , vanishes. TO wavelengths are important in fundamental and applied physics, offering a versatile tool in quantum state engineering [24].…”

Excited-band Bloch oscillations for precision atom interferometry

“…However, the performance was limited by the efficiency of momentum transfer, resulting in signal reduction for large momenta. Comparing the momentum transfer efficiency of 98.45% per k in [18] with the highest values in Fig.6(e), we can conservatively expect a four-fold increase in momentum separation with magic-depth excited-state BOs, leading to a sixteen-fold improvement in sensitivity to α for the same interferometer time. By operating at T BO,opt for b = 4 to reduce the acceleration time, and in a vertical geometry to increase the free evolution time, an overall improvement of more than a factor of 100 is attainable, allowing for a sub-partper-billion measurement of the fine structure constant and consequent test of QED theory.…”

“…The sinusoidal fit returns a visibility of 13% and a phase error δΦ = 0.57 rad. Our current level of light intensity fluctuations of < 2% [18], should contribute < 40 mrad to the phase uncertainty (arising from the local curvature of E at U MD and detailed below) [23]. The lower visibility and higher phase noise observed in Fig.…”