Coherent quantum state storage and transfer between two phase qubits via a resonant cavity (original) (raw)

Nature volume 449, pages 438–442 (2007)Cite this article

Abstract

As with classical information processing, a quantum information processor requires bits (qubits) that can be independently addressed and read out, long-term memory elements to store arbitrary quantum states1,2, and the ability to transfer quantum information through a coherent communication bus accessible to a large number of qubits3,4. Superconducting qubits made with scalable microfabrication techniques are a promising candidate for the realization of a large-scale quantum information processor5,6,7,8,9. Although these systems have successfully passed tests of coherent coupling for up to four qubits10,11,12,13, communication of individual quantum states between superconducting qubits via a quantum bus has not yet been realized. Here, we perform an experiment demonstrating the ability to coherently transfer quantum states between two superconducting Josephson phase qubits through a quantum bus. This quantum bus is a resonant cavity formed by an open-ended superconducting transmission line of length 7 mm. After preparing an initial quantum state with the first qubit, this quantum information is transferred and stored as a nonclassical photon state of the resonant cavity, then retrieved later by the second qubit connected to the opposite end of the cavity. Beyond simple state transfer, these results suggest that a high-quality-factor superconducting cavity could also function as a useful short-term memory element. The basic architecture presented here can be expanded, offering the possibility for the coherent interaction of a large number of superconducting qubits.

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Figure 1: Schematic description of the experiment set-up.

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Figure 2: Demonstration of strongly coupled circuit QED.

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Figure 3: Experimental data showing the quantum state transfer from qubit A to qubit B via the cavity.

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Figure 4: Demonstration of the coherent transfer of a quantum state through the quantum bus.

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Acknowledgements

We gratefully acknowledge discussions with J. Aumentado, K. Cicak, K. Osborne, R. Schoelkopf and D. Wineland. This work was financially supported by the NIST and the DTO.

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Authors and Affiliations

  1. National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA,
    Mika A. Sillanpää, Jae I. Park & Raymond W. Simmonds

Authors

  1. Mika A. Sillanpää
  2. Jae I. Park
  3. Raymond W. Simmonds

Corresponding author

Correspondence toRaymond W. Simmonds.

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Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

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Sillanpää, M., Park, J. & Simmonds, R. Coherent quantum state storage and transfer between two phase qubits via a resonant cavity.Nature 449, 438–442 (2007). https://doi.org/10.1038/nature06124

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