Atom-chip Bose-Einstein condensation in a portable vacuum cell

Abstract

A $^{87}\mathrm{Rb}$ Bose-Einstein condensate (BEC) is produced in a portable atom-chip system less than $30\ifmmode\times\else\texttimes\fi{}30\ifmmode\times\else\texttimes\fi{}15\phantom{\rule{0.3em}{0ex}}\mathrm{cm}$, where the ultrahigh vacuum is maintained by a small, $8\phantom{\rule{0.3em}{0ex}}\mathrm{L}∕\mathrm{s}$, ion pump and nonevaporable getter. An aluminum nitride chip with lithographically patterned copper is used to seal the vacuum system, provide the electrical feedthroughs, and create the magnetic trap potentials. All cooling and trapping processes occur $0.6--2.5\phantom{\rule{0.3em}{0ex}}\mathrm{mm}$ from ambient laboratory air. A condensate of about 2000 $^{87}\mathrm{Rb}$ atoms in $F=2,{m}_{F}=2$ is achieved after $4.21\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ of rf forced evaporation. A magneto-optical trap lifetime of $30\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ indicates the vacuum near the chip surface is about ${10}^{\ensuremath{-}10}\phantom{\rule{0.3em}{0ex}}\text{torr}$. This work suggests that a chip-based BEC-compatible vacuum system can occupy a volume of less than $0.5\phantom{\rule{0.3em}{0ex}}\mathrm{L}$.