Y. Lu

Deterministic loading and phase shaping of microwaves onto a single artificial atom

  1. W.-J. Lin,
  2. Y. Lu,
  3. P. Y. Wen,
  4. Y.-T. Cheng,
  5. C.-P. Lee,
  6. K.-T. Lin,
  7. K.-H. Chiang,
  8. M. C. Hsieh,
  9. J. C. Chen,
  10. C.-S. Chuu,
  11. F. Nori,
  12. A. F. Kockum,
  13. G.-D. Lin,
  14. P. Delsing,
  15. and I.-C. Hoi
Loading quantum information deterministically onto a quantum node is an important step towards a quantum network. Here, we demonstrate that coherent-state microwave photons, with anoptimal temporal waveform, can be efficiently loaded onto a single superconducting artificial atom in a semi-infinite one-dimensional (1D) transmission-line waveguide. Using a weak coherent state (average photon number N<<1 with an exponentially rising waveform, whose time constant matches the decoherence time of the artificial atom, we demonstrate a loading efficiency of above 94% from 1D semi-free space to the artificial atom. We also show that Fock-state microwave photons can be deterministically loaded with an efficiency of 98.5%. We further manipulate the phase of the coherent state exciting the atom, enabling coherent control of the loading process. Our results open up promising applications in realizing quantum networks based on waveguide quantum electrodynamics (QED).[/expand]
arxiv pdf

Random access quantum information processors

  1. R. K. Naik,
  2. N. Leung,
  3. S. Chakram,
  4. P. Groszkowski,
  5. Y. Lu,
  6. N. Earnest,
  7. D. C. McKay,
  8. Jens Koch,
  9. and D.I. Schuster
Qubit connectivity is an important property of a quantum processor, with an ideal processor having random access — the ability of arbitrary qubit pairs to interact directly. Here,
we implement a random access superconducting quantum information processor, demonstrating universal operations on a nine-bit quantum memory, with a single transmon serving as the central processor. The quantum memory uses the eigenmodes of a linear array of coupled superconducting resonators. The memory bits are superpositions of vacuum and single-photon states, controlled by a single superconducting transmon coupled to the edge of the array. We selectively stimulate single-photon vacuum Rabi oscillations between the transmon and individual eigenmodes through parametric flux modulation of the transmon frequency, producing sidebands resonant with the modes. Utilizing these oscillations for state transfer, we perform a universal set of single- and two-qubit gates between arbitrary pairs of modes, using only the charge and flux bias of the transmon. Further, we prepare multimode entangled Bell and GHZ states of arbitrary modes. The fast and flexible control, achieved with efficient use of cryogenic resources and control electronics, in a scalable architecture compatible with state-of-the-art quantum memories is promising for quantum computation and simulation.
arxiv pdf