Bose-Einstein Condensate ``Level'': a tool box for precesion measurement

A trapped, phase separated, two component Bose-Einstein condensate (BEC) can be configured to give a single BEC bubble that floats freely in the surrounding BEC. We point out that this system gives a unique template to carry out mesoscopic quantum studies and to detect weak forces. We demonstrate the detection capabilities by proposing and studying a ``Quantum Level'' for fundamental quantum fluctuation studies and for mapping the potential energy landscape near a surface with exquisite accuracy. The above method open up a new avenue for research where the quantum state of a trapped ultra-cold gases such as a BEC is cast as a measurement-tool rather than a system-under-investigation.