Carlos Sabín, Angela White, Lucia Hackermuller, Ivette Fuentes
We introduce a primary thermometer which measures the temperature of a Bose-Einstein Condensate ranging from the sub nK regime to the condensate critical temperature. We show, using Fisher information, that the precision of our technique improves the state of the art in thermometry. The temperature of the condensate is mapped onto the quantum phase of an array of atomic dots that interact with the system for short times. We show that the highest precision is achieved when the phase is dynamical rather than geometric and when it is detected through Ramsey interferometry. Entangling the atomic dots can be used to further improve the precision and reach the Heisenberg limit. Standard techniques to determine the temperature of a condensate involve an indirect estimation through mean particle velocities made after releasing the condensate. In contrast to these destructive measurements, our method involves a negligible disturbance of the system.
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http://arxiv.org/abs/1303.6208
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