Abstract
We introduce a primary thermometer which measures the temperature of a Bose-Einstein Condensate in the sub-nK regime. We show, using quantum Fisher information, that the precision of our technique improves the state-of-the-art in thermometry in the sub-nK regime. The temperature of the condensate is mapped onto the quantum phase of an atomic dot that interacts 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. 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.
Highlights
We introduce a primary thermometer which measures the temperature of a Bose-Einstein Condensate in the sub-nK regime
The temperature of the condensate is mapped onto the quantum phase of an atomic dot that interacts with the system for short times
In this paper we show how an atomic quantum dot immersed within the condensate can be used to measure the temperature of the condensate with high precision and a negligible disturbance of the system
Summary
We introduce a primary thermometer which measures the temperature of a Bose-Einstein Condensate in the sub-nK regime. Bose Einstein Condensates (BECs)[1] allow the study of quantum effects in systems consisting of up to 108 atoms by cooling them to regimes in which the individual atomic wavefunctions overlap. At temperatures of a few nK and below this method has low spatial resolution and can only be applied reliably if the condensate is allowed to freely expand for a given time[11] Another example is noise thermometry with two coupled Bose-Einstein condensates[12], which has been implemented in a regime in which quantum fluctuations are small (50–80 nK). The scheme can be implemented using an optical lattice with a single atom per site[27], where each atom interacts at a different time with the condensate This system constitutes a primary thermometer which measures the temperatures ranging from the sub nK regime to the condensate critical temperature
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