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Controlled collisions for multi-particle entanglement of optically trapped atoms

Abstract

Entanglement lies at the heart of quantum mechanics, and in recent years has been identified as an essential resource for quantum information processing and computation1,2,3,4. The experimentally challenging production of highly entangled multi-particle states is therefore important for investigating both fundamental physics and practical applications. Here we report the creation of highly entangled states of neutral atoms trapped in the periodic potential of an optical lattice. Controlled collisions between individual neighbouring atoms are used to realize an array of quantum gates, with massively parallel operation. We observe a coherent entangling–disentangling evolution in the many-body system, depending on the phase shift acquired during the collision between neighbouring atoms. Such dynamics are indicative of highly entangled many-body states; moreover, these are formed in a single operational step, independent of the size of the system5,6.

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Figure 1: Schematic multiple quantum gate sequences based on controlled interactions.
Figure 2: Experimentally measured Ramsey fringes for different hold times thold during which atoms undergo a controlled collisional interaction with their neighbouring atoms.
Figure 3: Visibility of Ramsey fringes versus hold times on neighbouring lattice sites for the experimental sequence similar to the one displayed in Fig. 1a.
Figure 4: Spatial interference patterns recorded after applying the multiple quantum gate sequence of Fig. 1b for different collisional interaction times thold.
Figure 5: Visibility of the spatial interference patterns versus different collisional interaction times thold.

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Acknowledgements

We thank H. Briegel and I. Cirac for discussions, and A. Altmeyer and T. Best for experimental assistance. This work was supported by the EU under the QUEST programme, the AFOSR and the Bayerische Forschungsstiftung.

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Correspondence to Immanuel Bloch.

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Mandel, O., Greiner, M., Widera, A. et al. Controlled collisions for multi-particle entanglement of optically trapped atoms. Nature 425, 937–940 (2003). https://doi.org/10.1038/nature02008

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