Tunable spin–spin interactions and entanglement of ions in separate potential wells


Quantum simulation1,2—the use of one quantum system to simulate a less controllable one—may provide an understanding of the many quantum systems which cannot be modelled using classical computers. Considerable progress in control and manipulation has been achieved for various quantum systems3,4,5, but one of the remaining challenges is the implementation of scalable devices. In this regard, individual ions trapped in separate tunable potential wells are promising6,7,8. Here we implement the basic features of this approach and demonstrate deterministic tuning of the Coulomb interaction between two ions, independently controlling their local wells. The scheme is suitable for emulating a range of spin–spin interactions, but to characterize the performance of our set-up we select one that entangles the internal states of the two ions with a fidelity of 0.82(1) (the digit in parentheses shows the standard error of the mean). Extension of this building block to a two-dimensional network, which is possible using ion-trap microfabrication processes9, may provide a new quantum simulator architecture with broad flexibility in designing and scaling the arrangement of ions and their mutual interactions. To perform useful quantum simulations, including those of condensed-matter phenomena such as the fractional quantum Hall effect, an array of tens of ions might be sufficient4,10,11.

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Figure 1: Microfabricated surface-electrode trap.
Figure 2: Motional spectroscopy of two coupled ions.
Figure 3: Characterizing the spin–spin coupling interaction between ions in separate trapping zones.


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We thank K. McCormick, A. Keith and D. Allcock for comments on the manuscript. This research was funded by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), ONR, and the NIST Quantum Information Program. All statements of fact, opinion or conclusions contained herein are those of the authors and should not be construed as representing the official views or policies of IARPA or the ODNI. This work, a submission of NIST, is not subject to US copyright.

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A.C.W. and D.L. designed the experiment, developed components of the experimental apparatus, collected data, analysed results and wrote the manuscript. D.L. developed the theory. Y.C. fabricated the ion-trap chip. K.R.B. built components of the apparatus, most notably the cryostat, and participated in the early design phase of the experiment. E.K. assisted with data analysis. D.J.W. participated in the design and analysis of the experiment. All authors discussed the results and the text of the manuscript.

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Correspondence to A. C. Wilson.

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Wilson, A., Colombe, Y., Brown, K. et al. Tunable spin–spin interactions and entanglement of ions in separate potential wells. Nature 512, 57–60 (2014). https://doi.org/10.1038/nature13565

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