Y. Xu

Witnessing quantum resource conversion within deterministic quantum computation using one pure superconducting qubit

  1. W. Wang,
  2. B. Yadin,
  3. Y. Ma,
  4. J. Ma,
  5. Y. Xu,
  6. L. Hu,
  7. H. Wang,
  8. Y. P. Song,
  9. Mile Gu,
  10. and L. Sun
Deterministic quantum computation with one qubit (DQC1) is iconic in highlighting that exponential quantum speedup may be achieved with negligible entanglement. Its discovery catalyzed
heated study of general quantum resources, and various conjectures regarding their role in DQC1’s performance advantage. Coherence and discord are prominent candidates, respectively characterizing non-classicality within localized and correlated systems. Here we realize DQC1 within a superconducting system, engineered such that the dynamics of coherence and discord can be tracked throughout its execution. We experimentally confirm that DQC1 acts as a resource converter, consuming coherence to generate discord during its operation. Our results highlight superconducting circuits as a promising platform for both realizing DQC1 and related algorithms, and experimentally characterizing resource dynamics within quantum protocols.
arxiv pdf

Perfect remote quantum state transfer in a superconducting qubit chain with parametrically tunable couplings

  1. X. Li,
  2. Y. Ma,
  3. J. Han,
  4. Tao Chen,
  5. Y. Xu,
  6. W. Cai,
  7. H. Wang,
  8. Y. P. Song,
  9. Zheng-Yuan Xue,
  10. Zhang-qi Yin,
  11. and Luyan Sun
Faithfully transferring quantum state is essential for quantum information processing. Here, we demonstrate a fast (in 84~ns) and high-fidelity (99.2%) quantum state transfer in a
chain of four superconducting qubits with nearest-neighbor coupling. This transfer relies on full control of the effective couplings between neighboring qubits, which is realized only by parametrically modulating the qubits without increasing circuit complexity. Once the couplings between qubits fulfill specific ratio, a perfect quantum state transfer can be achieved in a single step, therefore robust to noise and accumulation of experimental errors. This quantum state transfer can be extended to a larger qubit chain and thus adds a desirable tool for future quantum information processing. The demonstrated flexibility of the coupling tunability is suitable for quantum simulation of many-body physics which requires different configurations of qubit couplings.
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