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Dynamics of an open double quantum dot system via quantum measurement
摘要： We study the dynamics of a double quantum dot (DQD) system interacting with a Gaussian white noise (GWN) environment which is measured by a quantum point contact (QPC) device. With both the transverse and longitudinal noise taken into account, we utilize an effective method by adding an additional Bloch vector to calculate the cumulant generating functions of the electron transfer in the QPC detector based on the full counting statistics. We study the average detector current, Fano factor, and average waiting time of the electron transfer in the presence of decoherence effects of the DQD system caused by both the QPC and the GWN environment. It indicates that the decoherence effects arising from the QPC and the GWN environment have obviously different influences on the electron transfer detected by the QPC device in both short-time and long-time limits. It is shown that the measurement process would localize the electron in a DQD in a short time and that the distribution of the average current and Fano factor versus level displacement in long-time limit are broadened due to the interaction between the system and GWN environment, which provides a reliable method to explore the dynamical behavior of an open quantum system and to extract the characteristics of the environment by analyzing the detector outcome. Our results provide theoretical support for studies of quantum measurement in a semiconductor device affected by a fluctuant environment.
关键词： full counting statistics,Gaussian white noise,quantum point contact,double quantum dot,decoherence
更新于2025-09-23 15:21:01
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Anomalous Fano Resonance in Double Quantum Dot System Coupled to Superconductor
摘要： We analyze the influence of a local pairing on the quantum interference in nanoscopic systems. As a model system we choose the double quantum dot coupled to one metallic and one superconducting electrode in the T-shape geometry. The analysis is particularly valuable for systems containing coupled objects with considerably different broadening of energy levels. In such systems, the scattering of itinerant electrons on a discrete (or narrow) energy level gives rise to the Fano-type interference. Systems with induced superconducting order, along well understood fano resonances, exhibit also another features on the opposite side of the Fermi level. The lineshape of these resonances differs significantly from their reflection on the opposite side of the Fermi level, and their origin was not fully understood. Here, considering the spin-polarized tunneling model, we explain a microscopic mechanism of a formation of these resonances and discuss the nature of their uncommon lineshapes. We show that the anomalous Fano profiles originate solely from the pairing of nonscattered electrons with scattered ones. We investigate also the interplay of each type of resonances with the Kondo physics and discuss the resonant features in differential conductivity.
关键词： Kondo physics,Fano-type interference,quantum interference,spin-polarized tunneling model,differential conductivity,double quantum dot,superconducting electrode,nanoscopic systems
更新于2025-09-23 15:19:57
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Lasing in a coupled hybrid double quantum dot-resonator system
摘要： We theoretically investigate the possibility of lasing in an electromagnetic resonator coupled to a voltage-biased hybrid double quantum dot comprised of a double quantum dot tunnel coupled simultaneously to a normal metal and a superconducting lead. Using a unitary transformation, we derive a resonator-double quantum dot interaction Hamiltonian in the rotating-wave approximation which reveals the fact that lasing in this system is mediated by electron transitions between Andreev energy levels in the system’s density of states. Moreover, by employing a Markovian master equation incorporating dissipation effects for the electronic and photonic degrees of freedom, we numerically calculate the steady-state reduced density matrix of the system from which we determine the average photon number and its statistics in the resonator in various parameter regimes. We ?nd that at some appropriate parameter con?gurations, lasing can be considerably enhanced due to the possibility of electron transitions between multiple Andreev levels in the system.
关键词： lasing,Andreev energy levels,hybrid double quantum dot,electromagnetic resonator,Markovian master equation
更新于2025-09-23 15:19:57
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Light emission properties in a double quantum dot molecule immersed in a cavity: Phonon-assisted tunneling
摘要： Two main mechanisms dictate the tunneling process in a double quantum dot: overlap of excited wave functions, effectively described as a tunneling rate, and phonon-assisted tunneling. In this paper, we study different regimes of tunneling that arise from the competition between these two mechanisms in a double quantum dot molecule immersed in a unimodal optical cavity. We show how such regimes affect the mean number of excitations in each quantum dot and in the cavity, the spectroscopic resolution and emission peaks of the photoluminescence spectrum, and the second-order coherence function which is an indicator of the quantumness of emitted light from the cavity.
关键词： Double quantum dot,Light-matter interaction,Second-order coherence function,Phonon-assisted tunneling
更新于2025-09-16 10:30:52
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The transition from double to single quantum dot induced by THz laser field
摘要： The combined influence of an intense laser field and a homogeneous magnetic field is considered on laterally coupled double quantum dot with isotropic and anisotropic parabolic confinement. It is shown that intense laser field can recover typical properties to a single quantum dot: it creates Fock–Darwin states in a double quantum dot with anisotropic confinement. Also, the laser and the magnetic field effects on the intraband absorption spectrum reveal blueshift if the laser field is increased and redshift with the gain of the magnetic field.
关键词： Double quantum dot,Fock–Darwin states,Intense laser field,Magnetic field,Intraband absorption
更新于2025-09-16 10:30:52