O. A. Chuikin

Stimulated emission for a three-level artificial atom in waveguide quantum electrodynamics

  1. O. A. Chuikin,
  2. Ya. S. Greenberg,
  3. V. V. Taravkova,
  4. and O. V. Kibis
This work is devoted to a theoretical study of the interaction of a quantum three-level ladder system with a continuous electromagnetic field in a one-dimensional open waveguide. Weconsider a situation closely resembling stimulated emission – the scattering of a single-photon exponential pulse by an excited three-level emitter. Using the real-space formalism, we obtain an analytical expression for the wavefunction of our system. We show that, for the low anharmonicity of a three-level system inherent to a transmon (the most common type of artificial atom), the influence of the third level can have a significant effect on the system’s behavior. Namely, the presence of the third level largely suppresses the stimulated emission effect if the relative anharmonicity is lower than |αr|<4%. However, for a three-level system, it is possible to obtain correlation effects such as photon bunching in the reflected field, which can also be 'switched off' by tuning the incident photon parameters.[/expand]
arxiv pdf

Superradiant emission spectra of a two-qubit system in circuit quantum electrodynamics

  1. Ya. S. Greenberg,
  2. and O. A. Chuikin
In this paper we study the spontaneous emission spectra and the emission decay rates of a simplest atom system that exhibits sub- and superradiant properties: a system which consists
of two artificial atoms (superconducting qubits) embedded in a one-dimensional open waveguide. The calculations are based on the method of the transition operator which was firstly introduced by R. H. Lehmberg to theoretically describe the spontaneous emission of two-level atoms in a free space. We obtain the explicit expressions for the photon radiation spectra and the emission decay rates for different initial two-qubit configurations with one and two excitations. For every initial state we calculate the radiation spectra and the emission decay rates for different effective distances between qubits. In every case, a decay rate is compared with a single qubit decay to show the superradiant or subradiant nature of a two-qubit decay with a given initial state.
arxiv pdf