Evidence of Noise-Suppression with Superconductive Atom Chip


Tetsuya Mukai, Christoph Hufnagel, and Fujio Shimizu*
Physical Science Laboratory
*The University of Electro-Communications / NTT Research Professor

 Strong confinement in trapping neutral atoms is necessary to realize full quantum control over atomic system. Although micro-magnetic trap on chip is a promising candidate to realize a strong trapping confinement, the electro-magnetic noise and thermal noise reduce the trapping lifetime seriously in the vicinity of a chip surface. To overcome this problem we developed a persistent supercurrent atom chip [1], and in 2008 we have shown an evidence of noise-suppression of superconductive atom chip even in the vicinity of a strip with large transporting current.
 The experiment was done by measuring the number of atoms leftover after keeping atoms in a chip potential with specific atom-surface distance. An absorption measurement with reflected image was employed for precise trap height identification (Fig. 1). The chip pattern that we used for this experiment has an MgB2 superconductive loop circuit as shown in Fig. 2. Figure 3 represents the measured trapping lifetime over the atom-surface distance, which was deduced from the decay late of trapped atoms. The lifetime of our persistent supercurrent atom chip was reaching more than an order longer than that of normal conductive counterparts. With miniaturized wire strip, we will realize a strong trapping confinement in quantum regime, and in future we will pursue the realization of full quantum control over atomic system.
 This research was partially supported by Japan Science and Technology Agency CREST.

[1] T. Mukai, C. Hufnagel et al., Phys. Rev. Lett. 98 (2007) 260407.

Fig. 1. Sample absorption image of trapped atomic cloud with reflection in the vicinity of a chip surface.
Fig. 2. (a) Chip pattern of persistent supercurrent atom chip. (b) Cross section of the chip wire and the trap geometry.
Fig. 3. Trapping lifetime over the atom-surface distance. (Ref: Eur. Phys. J. D 51 (2009) 173 and Phys. Rev. A 66 (2002) 041604.)

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