L. M. Duan

Verifying quantum information scrambling dynamics in a fully controllable superconducting quantum simulator

  1. J.-H. Wang,
  2. T.-Q. Cai,
  3. X.-Y. Han,
  4. Y.-W Ma,
  5. Z. L. Wang,
  6. Z.-H Bao,
  7. Y. Li,
  8. H.-Y Wang,
  9. H.-Y Zhang,
  10. L.-Y Sun,
  11. Y.-K. Wu,
  12. Y. P. Song,
  13. and L. M. Duan
Quantum simulation elucidates properties of quantum many-body systems by mapping its Hamiltonian to a better-controlled system. Being less stringent than a universal quantum computer,
noisy small- and intermediate-scale quantum simulators have successfully demonstrated qualitative behavior such as phase transition, localization and thermalization which are insensitive to imperfections in the engineered Hamiltonian. For more complicated features like quantum information scrambling, higher controllability will be desired to simulate both the forward and the backward time evolutions and to diagnose experimental errors, which has only been achieved for discrete gates. Here, we study the verified scrambling in a 1D spin chain by an analogue superconducting quantum simulator with the signs and values of individual driving and coupling terms fully controllable. We measure the temporal and spatial patterns of out-of-time ordered correlators (OTOC) by engineering opposite Hamiltonians on two subsystems, with the Hamiltonian mismatch and the decoherence extracted quantitatively from the scrambling dynamics. Our work demonstrates the superconducting system as a powerful quantum simulator.
arxiv pdf

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.
arxiv pdf

Quantum network of superconducting qubits through opto-mechanical interface

  1. Zhang-qi Yin,
  2. W. L. Yang,
  3. L. Sun,
  4. and L. M. Duan
We propose a scheme to realize quantum networking of superconducting qubits based on the opto-mechanical interface. The superconducting qubits interact with the microwave photons, which
then couple to the optical photons through the opto-mechanical interface. The interface generates a quantum link between superconducting qubits and optical flying qubits with tunable pulse shapes and carrier frequencies, enabling transmission of quantum information to other superconducting or atomic qubits. We show that the scheme works under realistic experimental conditions and it also provides a way for fast initialization of the superconducting qubits under 1 K instead of 20 mK operation temperature.
arxiv pdf