Atom interferometry using Kapitza-Dirac scattering in a magnetic trap

We demonstrate two atom interferometric schemes based on Kapitza-Dirac scattering in a magnetic trap. In the first method, two Kapitza-Dirac scattering pulses are applied with a small time delay between them. High contrast interference is observed both using a thermal cloud and a Bose-Einstein condensate (BEC). In the second method, two Kapitza-Dirac scattering pulses are applied to a BEC with a time separation sufficiently large that the interfering orders complete half an oscillation in the magnetic trap; this enables interferometry between spatially separated paths.

Figure 1

(a) Schematic of the first interferometry method, represented in momentum space. This method can be used for both a thermal cloud and a BEC. (b) Schematic of the second interferometry method, represented in position space. This method can be used to realize a large-separation atom interferometer.

Figure 2

(a) Thermal-cloud interference with different time intervals, $\Delta t$, between Kapitza-Dirac scattering pulses. (b) Fringe period of interference for a thermal cloud vs $1/\Delta t$. (c) BEC interference, for $\Delta t=420\mu \text{s}$ between pulses.

Figure 3

(Color online) Experimental and simulated interference patters for $\omega =45\text{Hz}$, $\Delta t=200\mu \text{s}$, $t_{\text{TOF}}=20\text{ms}$, and the indicated temperature values. Experimental temperatures are estimated using TOF, and have uncertainties of $\pm 50\text{nK}$.

Figure 4

(Color online) Asymmetry between the number of BEC atoms with a final momentum $+2p_{\text{r}}$, $P_{+}$, and the number of BEC atoms with a final momentum $-2p_{\text{r}}$, $P_{-}$, defined by $A=\frac{P_{+}-P_{-}}{P_{+}+P_{-}}$, as a function of the initial momentum $p_0$, for $\Delta t=100\mu \text{s}$. Squares are experimental data; solid line is a simulation based on propagators; dashed line is an analytic calculation, following Eq. (5).

Figure 5

Large-separation atom interferometer. After undergoing a half-period oscillation in the magnetic trap: (a) BEC interference can clearly be seen for various $\Delta t$; (b) a thermal cloud shows weak interference $\left(\Delta t=8.3\text{ms}\right)$.

Figure 6

Interference after a full-period oscillation. $\Delta t=16.5\text{ms}$.