A two-fold quantum delayed-choice experiment in a superconducting circuit

  1. K. Liu,
  2. Y. Xu,
  3. W. Wang,
  4. Shi-Biao Zheng,
  5. Tanay Roy,
  6. Suman Kundu,
  7. Madhavi Chand,
  8. A. Ranadive,
  9. R. Vijay,
  10. Y. P. Song,
  11. L. M. Duan,
  12. and L. Sun
We propose and experimentally demonstrate a two-fold quantum delayed-choice experiment where wave or particle nature of a superconducting interfering device can be post-selected twice after the interferometer. The wave-particle complementarity is controlled by a quantum which-path detector (WPD) in a superposition of its on and off states implemented through a superconducting cavity. The WPD projected to its on state records which-path information, which manifests the particle nature and destroys the interference associated with wave nature of the system. In our experiment, we can recover the interference signal through a quantum eraser even if the WPD has selected out the particle nature in the first round of delayed-choice detection, showing that a quantum WPD adds further unprecedented controllability to test of wave-particle complementarity through the peculiar quantum delayed-choice measurements.
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