A millimeter magnetic trap for a dual (⁸⁵Rb and ⁸⁷Rb) species atom interferometer

We present a magnetic trap for cold atoms near a surface of a millimeter-sized atom chip. The trap allows us to capture a large number of atoms with modest electrical currents (40 A) and to generate large magnetic gradients (>300 G cm^-1). Here we report a mixture containing 6 × 10⁹ atoms for the two rubidium isotopes ⁸⁷Rb and ⁸⁵Rb. This device does not require cleanroom facilities nor micro-machining technologies which makes its construction easier. In addition our design allows the implementation of an optical dipole trap with a laser beam passing through the chip.