Dephasing-insensitive quantum information storage and processing with superconducting qubits

  1. Qiujiang Guo,
  2. Shi-Biao Zheng,
  3. Jianwen Wang,
  4. Chao Song,
  5. Pengfei Zhang,
  6. Kemin Li,
  7. Wuxin Liu,
  8. Hui Deng,
  9. Keqiang Huang,
  10. Dongning Zheng,
  11. Xiaobo Zhu,
  12. H. Wang,
  13. C.-Y. Lu,
  14. and Jian-Wei Pan
A central task towards building a practical quantum computer is to protect individual qubits from decoherence while retaining the ability to perform high-fidelity entangling gates involving
arbitrary two qubits. Here we propose and demonstrate a dephasing-insensitive procedure for storing and processing quantum information in an all-to-all connected superconducting circuit involving multiple frequency-tunable qubits, each of which can be controllably coupled to any other through a central bus resonator. Although it is generally believed that the extra frequency tunability enhances the control freedom but induces more dephasing impact for superconducting qubits, our results show that any individual qubit can be dynamically decoupled from dephasing noise by applying a weak continuous and resonant driving field whose phase is reversed in the middle of the pulse. More importantly, we demonstrate a new method for realizing two-qubit phase gate with inherent dynamical decoupling via the combination of continuous driving and qubit-qubit swapping coupling. We find that the weak continuous driving fields not only enable the conditional dynamics essential for quantum information processing, but also protect both qubits from dephasing during the gate operation.

10-qubit entanglement and parallel logic operations with a superconducting circuit

  1. Chao Song,
  2. Kai Xu,
  3. Wuxin Liu,
  4. Chuiping Yang,
  5. Shi-Biao Zheng,
  6. Hui Deng,
  7. Qiwei Xie,
  8. Keqiang Huang,
  9. Qiujiang Guo,
  10. Libo Zhang,
  11. Pengfei Zhang,
  12. Da Xu,
  13. Dongning Zheng,
  14. Xiaobo Zhu,
  15. H. Wang,
  16. Y.-A. Chen,
  17. C.-Y. Lu,
  18. Siyuan Han,
  19. and J.-W. Pan
Here we report on the production and tomography of genuinely entangled Greenberger-Horne-Zeilinger states with up to 10 qubits connecting to a bus resonator in a superconducting circuit,
where the resonator-mediated qubit-qubit interactions are used to controllably entangle multiple qubits and to operate on different pairs of qubits in parallel. The resulting 10-qubit density matrix is unambiguously probed, with a fidelity of 0.668±0.025. Our results demonstrate the largest entanglement created so far in solid-state architectures, and pave the way to large-scale quantum computation.