Two-electron double quantum dot coupled to coherent photon and phonon fields

Vasileios N. Stavrou, Xuedong Hu

利正 藤澤

Y.-Y. Liu, Karl D. Petersson, J. Stehlik +2 more

We study a voltage biased InAs double quantum dot (DQD) that is coupled to a superconducting transmission line resonator. Inelastic tunneling in the DQD is mediated by electron phonon coupling and coupling to the cavity mode. We show that electronic transport through the DQD leads to photon emission from the cavity at a rate of 10 MHz. With a small cavity drive field, we observe a gain of up to 15 in the cavity transmission. Our results are analyzed in the context of existing theoretical models and suggest that it may be necessary to account for inelastic tunneling processes that proceed via simultaneous emission of a phonon and a photon.

Kazuyuki Kuroyama, Sadashige Matsuo, Seigo Tarucha +1 more

We have theoretically studied phonon-mediated spin-flip processes of electrons in a GaAs double quantum dot (DQD) holding two spins, under a phonon temperature gradient over the DQD. Transition rates of interdot phonon-assisted tunnel processes and intradot spin-flip processes involving spin triplet states are formalized by the electron-phonon interaction accompanied with the spin-orbit interaction. The calculations of the spin-flip rates and the occupation probabilities of the spin-states in the two-electron DQD with respect to the phonon temperature difference between the dots are quantitatively consistent with our previous experiment. This theoretical study on the temperature gradient effect onto spins in coupled QDs would be essential for understanding spin-related thermodynamic physics.

L. Debora Contreras-Pulido, F. Rojas

We demonstrate theoretical stationary and dynamical generation of Bell states in a system of two parallel double quantum dots with one mobile electron each (proposed as two charge qubits) driven by an external potential difference applied to the second of the double dots. For coherent dynamics, it is shown that each one of the four Bell states is obtained through a suitable nonentangled initial condition as well as through the control of the time-dependent external electric field. We analyze dissipative effects on such state formation, due to the coupling with a thermal bath of phonons. Via a Markovian master equation approach, which includes the electron-phonon interaction, we found that Bell-state probabilities are preserved for very low temperature but are adversely affected as the temperature increases. In addition, we include concurrence and charge distribution calculations in order to characterize the double-dot array. This electrostatic mechanism could be of interest in quantum-computation, -information, and -communication schemes.

T. Mihaescu, A. Isar, M. A. Macovei

The quantum dynamics of a double quantum dot two-level system, coupled to a leaking microwave resonator mode, is theoretically investigated. The double quantum dot is driven by applying a continuous field giving rise to time-dependent modulations of its energy separation between the ground levels of each dot, forming the qubit. Therefore, the cavity resonances occur when the difference between the resonator and the qubit frequencies equals the multiple of the modulation frequency, respectively. In the strong Coulomb interaction limit and the weak couplings of the combined system, i.e. the qubit and the single-mode cavity, to corresponding electronic, phononic or photonic reservoirs, we have demonstrated that the output cavity electromagnetic field is formed of a single-photon flux obeying the sub-Poissonian quantum photon statistics. This was proved via Fano's factor behaviour or by comparing the resonator's second- and third-order photon correlation functions, respectively. The phonon, the cavity mode dephasing or the environmental temperatures influence on the quantum properties of the photons are also discussed.