Sensitive Measurement of Forces at the Micron Scale Using Bloch Oscillations of Ultracold Atoms

We show that Bloch oscillations of ultracold fermionic atoms in the periodic potential of an optical lattice can be used for a sensitive measurement of forces at the micrometer length scale, e.g., in the vicinity of a dielectric surface. In particular, the proposed approach allows us to perform a local and direct measurement of the Casimir-Polder force which is, for realistic experimental parameters, as large as ${10}^{-4}$ gravity.

Figure 1

Sketch of the physical situation considered in this Letter: an ultracold sample of fermionic atoms is trapped in a vertical optical lattice in proximity of a dielectric surface and performs Bloch oscillations under the combination of gravity and of the CP force.

Figure 2

Momentum distribution of a Fermi gas performing Bloch oscillations at different times within an oscillations period: solid lines are experimental data, dashed lines are theoretical calculations including adiabatic switch-off of the lattice. $E_F/2\delta =0.9$.

Figure 3

Relative shift $\Delta T_B/T_B$ of the Bloch oscillation period due to the CP force. The solid line is the prediction (4) using the thermal potential (3), the circles are the result of a numerical simulation as described in the text.

Figure 4

Upper panel (a) momentum distribution of a Fermi gas at a distance $D=10\mu \mathrm{m}$ from the surface at beginning (dashed line) and after 1000 periods of Bloch oscillations (solid line). Lower panel (b) momentum distribution of a BEC after 2 periods of Bloch oscillations.