Abstract

We consider the dephasing of two internal states |0⟩ and |1⟩ of a trapped impurity atom, a so-called atomic quantum dot (AQD), where only state |1⟩ couples to a Bose–Einstein condensate (BEC). A direct relation between the dephasing of the internal states of the AQD and the temporal phase fluctuations of the BEC is established. Based on this relation we suggest a scheme to probe BEC phase fluctuations non-destructively via dephasing measurements of the AQD. In particular, the scheme allows to trace the dependence of the phase fluctuations on the trapping geometry of the BEC.

Highlights

  • The coherence properties of Bose–Einstein condensates (BECs) have attracted considerable theoretical and experimental interest since the first experimental realization of BECs in trapped ultracold clouds of alkali atoms [1, 2]

  • We propose a scheme to measure temporal phase fluctuations of the BEC based on a single trapped impurity atom coupled to the BEC, hereafter called an atomic quantum dot (AQD) [10]

  • By identifying the combined system of the AQD and the BEC with an exactly solvable independent boson model [16]–[18], we show that the dephasing of the internal states due to the asymmetric interaction with the BEC is directly related to the temporal phase fluctuations

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Summary

Introduction

The coherence properties of Bose–Einstein condensates (BECs) have attracted considerable theoretical and experimental interest since the first experimental realization of BECs in trapped ultracold clouds of alkali atoms [1, 2]. We propose a scheme to measure temporal phase fluctuations of the BEC based on a single trapped impurity atom coupled to the BEC, hereafter called an atomic quantum dot (AQD) [10]. We consider an AQD with two internal states |0 and |1 , where we assume for simplicity that only state |1 undergoes collisional (s-wave scattering) interactions with the BEC This set-up could be implemented using spin-dependent optical potentials [11], where the impurity atom, trapped separately [12]–[14], and the BEC atoms correspond to different internal atomic states. By identifying the combined system of the AQD and the BEC with an exactly solvable independent boson model [16]–[18], we show that the dephasing of the internal states due to the asymmetric interaction with the BEC is directly related to the temporal phase fluctuations.

The model
Corrections due to a shallow potential
Application
Measurement of the internal states
Conclusion

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