Anton Frisk Kockum

The giant acoustic atom — a single quantum system with a deterministic time delay

  1. Lingzhen Guo,
  2. Arne Grimsmo,
  3. Anton Frisk Kockum,
  4. Mikhail Pletyukhov,
  5. and Göran Johansson
We investigate the quantum dynamics of a single transmon qubit coupled to surface acoustic waves (SAWs) via two distant connection points. Since the acoustic speed is five orders of
magnitude slower than the speed of light, the travelling time between the two connection points needs to be taken into account. Therefore, we treat the transmon qubit as a giant atom with a deterministic time delay. We find that the spontaneous emission of the system, formed by the giant atom and the SAWs between its connection points, initially follows a polynomial decay law instead of an exponential one, as would be the case for a small atom. We obtain exact analytical results for the scattering properties of the giant atom up to two-phonon processes by using a diagrammatic approach. The time delay gives rise to novel features in the reflection, transmission, power spectra, and second-order correlation functions of the system. Furthermore, we find the short-time dynamics of the giant atom for arbitrary drive strength by a numerically exact method for open quantum systems with a finite-time-delay feedback loop.
arxiv pdf

Quantum Acoustics with Surface Acoustic Waves

  1. Thomas Aref,
  2. Per Delsing,
  3. Maria K. Ekström,
  4. Anton Frisk Kockum,
  5. Martin V. Gustafsson,
  6. Göran Johansson,
  7. Peter Leek,
  8. Einar Magnusson,
  9. and Riccardo Manenti
It has recently been demonstrated that surface acoustic waves (SAWs) can interact with superconducting qubits at the quantum level. SAW resonators in the GHz frequency range have also
been found to have low loss at temperatures compatible with superconducting quantum circuits. These advances open up new possibilities to use the phonon degree of freedom to carry quantum information. In this paper, we give a description of the basic SAW components needed to develop quantum circuits, where propagating or localized SAW-phonons are used both to study basic physics and to manipulate quantum information. Using phonons instead of photons offers new possibilities which make these quantum acoustic circuits very interesting. We discuss general considerations for SAW experiments at the quantum level and describe experiments both with SAW resonators and with interaction between SAWs and a qubit. We also discuss several potential future developments.
arxiv pdf