Suspension of Atoms Using Optical Pulses, and Application to Gravimetry

Atoms from a ${}^{87}\mathrm{Rb}$ condensate are suspended against gravity using repeated reflections from a pulsed optical standing wave. Up to 100 reflections are observed, yielding suspension times of over 100 ms. The local gravitational acceleration can be determined from the pulse rate required to achieve suspension. Further, a gravitationally sensitive atom interferometer was implemented using the suspended atoms. This technique could potentially provide a precision measurement of gravity without requiring the atoms to fall a large distance.

Figure 1

Atom trajectories discussed in this Letter, shown with a common scale as indicated. (a) Bouncing atoms using order-1 reflections. (b) Bouncing atoms using order-2 reflections. (c) Interferometer produced with a combination of order-1 and order-2 reflections. Here the colored dashed curves show the two arms of the interferometer, and there are two possible output states. (d) More complex interferometer with large arm spacing. Trajectories (a)–(c) were implemented here.

Figure 2

Suspension of atoms using (a) order-1 and (b) order-2 reflection operations. Data points indicated the number of atoms remaining after the indicated number of reflections. In both cases, the horizontal scale corresponds to a total time of 125 ms.

Figure 3

Results of interferometer experiment. The upper graph shows the total phase shift observed in the output, in radians. The insets are sample plots of the fraction $f_{+}$ of atoms with $p=\hslash k$ exiting the interferometer. The cases of one cycle and 40 cycles are shown. The duration of one cycle is 2.4 ms. The residuals plotted in the lower graph are the difference between the measured phase and the linear fit; the oscillations are attributed to a transient magnetic field produced when the trap is turned off.