Double Quantum Dots as Dissipative Two Level Systems ( Quantum Dot Structures)

利正 藤澤

Kevin Ingersent

Tomosuke Aono, Kiyoshi Kawamura Kiyoshi Kawamura

A double quantum dot system is a typical example of a dissipative two level system. The ratio of the coupling of the two dots and the width of the energy level is the important parameter determining whether the quantum coherence can be seen clearly. Indications of quantum coherence between two dots appear not only in the stationary states but also in the relaxation processes from non-stationary states.

Alexander V. Tsukanov, I. Yu. Kateev

Abstract A circuit of a measuring chip for determining an arbitrary pure state of a charge qubit is proposed. The strength of the current flowing through a single-electron transistor in the steady-state mode depends on the state of the qubit. To enhance the sensitivity of the transistor, its working part is built from three quantum dots (QDs) with the energy levels forming a symmetric configuration. The parameters of the system are calculated using a microscopic model of two-dimensional QDs. The time dependences of the population of the structure’s states are obtained and the current strength, sensitivity, and measuring contrast as functions of the geometric parameters of the system are determined. The effect of dissipative processes related to the acoustic phonons on the measurements is investigated and the rates of electron relaxation and dephasing in a two-level system are calculated.

Runan Shang, Hai-Ou Li, Gang Cao +4 more

A double quantum dot defines a qubit by a two-level system. The coupling between two qubits induces a double two-level system into a four-level system. We study experimentally the coupling between two capacitive coupled GaAs/AlGaAs double quantum dots while tuning the energy detuning of each double quantum dot simultaneously. Applying microwave photons (at a frequency of 20 GHz) on this system and observing the resonance tunneling with a quantum point contact detector, we obtain an excitation spectrum which is consistent with the numerical simulation result of a coupled two-qubit Hamiltonian. This study demonstrates that a double quantum dot can be exploited as an extraordinary platform for controlled quantum gates.

Gu Zhang, E. Novais, Harold U. Baranger