Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Communications in Theoretical Physics

Effects of Electric and Magnetic Fields on Pure Dephasing of Exciton Qubits

Yunfei Liu, Xiao Jing-lin

Published Mar 1, 2009• 0 citations
Publisher

Abstract

In a two-dimensional quantum dot (QD) with parabolic confinement potential, we investigate pure dephasing due to deformation potential exciton-bulk longitudinal acoustic phonons (LAP) interaction for exciton qubits under the influence of external static electric and magnetic fields by adopting the full quantum-mechanical method of Kunihiro Kojima and Akihisa Tomita. The wave function is found and the dependence of the pure dephasing factor on the confinement length of the QD and time and temperature is discussed. We find the external electric and magnetic fields have important effects on pure dephasing of exciton qubits because exciton-LAP interaction increases, leading to more pure dephasing.

DOI
10.1088/0253-6102/51/3/32

Related papers

Effects of LA phonon on pure dephasing for exciton qubit

Yunfei Liu, Xiao Jing-lin, 河北科技师范学院数理系，秦皇岛 066004；内蒙古民族大学物理与电子信息学院，通辽 028043

In a parabolic quantum dot (QD), the exciton vacuum state and the exciton ground state may be employed as a two-level quantum system——a qubit. The pure dephaseing due to deformation potential exciton-bulk longitudinal acoustic phonon (LAP) interaction for the exciton qubit is investigated by using the reduce density matrix. The dependence of dephasing factor on time and the confinement length of the QD and temperature is calculated. It is shown that the pure dephasing factor increases quickly with increasing time when time is smaller than 2.5ps, and the dephasing time is of the order of ps. Even at absolute zero temperature, exciton-LAP interaction still causes excitonic dephasing. The pure dephasing factor increases with increasing temperature quickly when temperature is higher than 3K. At the same time, it is found that the confinement length of the QD has important effects on pure dephasing of qubit, the smaller the quantum size, the faster the pure dephasing is. The results show that using appropriate QD size at low temperature and using ultra-fast laser technology can effectively suppress pure dephasing due to exciton-LAP interaction.

Acta Physica Sinica•Jan 1, 2008•2 citations

Geometrical phases of excitonic qubits in quantum dots

Alagu Thilagam

We investigate the influence of phonon mediated interactions on the non-unitary evolution of geometrical phases in excitonic qubits formed in quantum dots entangled by pure Förster coupling. We consider decoherence to occur via acoustic phonons interacting through the deformation potential and piezoelectric coupling mechanisms. The influences of bath temperature, external electric field, quantum dot size and interdot distance on the evolution of geometrical phases are examined for the GaAs/AlGaAs material system. We extend the theory to determine the effect of dynamic decoupling employing ultrafast π-pulses on the evolution of geometrical phases in the presence of dephasing processes.

Journal of Physics Condensed Matter•Dec 19, 2008•4 citations

Phonon Dephasing of the Exciton in InAs / GaAs Quantum Dots

Andrzej Janutka, Lucjan Jacak, J. Krasnyj +1 more

The interaction of a exciton confined in a semiconductor quantum dot (QD) with bulk phonons (acoustical and optical) responsible for the exciton dephasing is studied. The decoherence of the exciton due to the creation of a polaron with long-living or decaying phonons is described. Characteristic dephasing times for an InAs / GaAs QD are estimated using Green function methods in order to determine fundamental time limitations for use of the QD exciton in quantum information processing.

Open Systems & Information Dynamics•Dec 1, 2004•0 citations

Influence of pure dephasing by phonons on exciton-photon interfaces: Quantum microscopic theory

Kunihiro Kojima, Akihisa Tomita

We have developed a full quantum microscopic theory to analyze the time evolution of transversal and longitudinal components of an exciton-single photon system coupled to bulk acoustic phonons. These components are subjected to two decay processes. One is radiative relaxation and the other is pure dephasing due to exciton-phonon interaction. The former results in a decay with an exponent linear to time, while the latter causes a faster initial decay than the radiative decay. We analyzed the dependence of the components on the duration of the input one-photon pulse, temperature, and radiative relaxation rates. Such a quantitative analysis is important for the developments of atom-photon interfaces which enable coherent transfer of quantum information between photons and atomic systems. We found that, for a GaAs spherical quantum dot in which the exciton interacts with bulk phonons, the maximal probability of the excited state can be increased up to 75%. This probability can be considered as the efficiency for quantum information transfer from photon to exciton.

arXiv:quant-ph/0702198•Physical Review B•May 15, 2006•7 citations

Decoherence of excitonic qubits in Förster coupled quantum dots

Alagu Thilagam, Max A. Lohe

We investigate phonon-assisted mechanisms which contribute to the decoherence of excitonic qubits in quantum dot systems coupled by a Förster-type transfer process. Using the Fermi Golden Rule, we derive explicit expressions for the relaxation and dephasing times for excitonic qubits interacting with acoustic phonons via both the deformation potential and piezoelectric coupling. The decoherence times computed using the Fermi Golden Rule are consistent with those estimated using Bloch–Redfield theory at interdot tunnelling energies small enough for Markovian theories to be valid. Our results show that renormalization of interdot tunnelling frequencies due to phonon interactions is influenced mainly by bias and lattice temperature in GaAs/AlGaAs quantum dot systems.

Journal of Physics Condensed Matter•Jul 17, 2008•8 citations

Effect of inter-dot distance on excitonic dephasing in quantum dot chains

Pier Paolo Marchisio, Irene D’Amico

We present a study of the dephasing of an excitonic qubit trapped within a chain of two semiconductor quantum dots immersed in a bulk material. We consider a specific excitonic wave-function which spreads across the chain. The source of the dephasing is the phonon field of the bulk material interacting with the single exciton within the structure. We show that an excitonic wave function which extends over more than one quantum dot is remarkably more robust against the dephasing. The details of dephasing depends on the distance which separates the two quantum dots. In particular, as this distance increases, the residual coherence increases up to a maximum value. However, the short-time dephasing is shown to be characterised by the appearance of a transient behavior. The actual duration of this transient is determined by the separation between the dots.

Journal of Physics Conference Series•Feb 1, 2010•0 citations
In a two-dimensional quantum dot (QD) with parabolic confinement potential, we investigate pure dephasing due to deformation potential exciton-bulk longitudinal acoustic phonons (LAP) interaction for exciton qubits under the influence of external static electric and magnetic fields by adopting the full quantum-mechanical method of Kunihiro Kojima and Akihisa Tomita. The wave function is found and the dependence of the pure dephasing factor on the confinement length of the QD and time and temperature is discussed. We find the external electric and magnetic fields have important effects on pure dephasing of exciton qubits because exciton-LAP interaction increases, leading to more pure dephasing.
In a parabolic quantum dot (QD), the exciton vacuum state and the exciton ground state may be employed as a two-level quantum system——a qubit. The pure dephaseing due to deformation potential exciton-bulk longitudinal acoustic phonon (LAP) interaction for the exciton qubit is investigated by using the reduce density matrix. The dependence of dephasing factor on time and the confinement length of the QD and temperature is calculated. It is shown that the pure dephasing factor increases quickly with increasing time when time is smaller than 2.5ps, and the dephasing time is of the order of ps. Even at absolute zero temperature, exciton-LAP interaction still causes excitonic dephasing. The pure dephasing factor increases with increasing temperature quickly when temperature is higher than 3K. At the same time, it is found that the confinement length of the QD has important effects on pure dephasing of qubit, the smaller the quantum size, the faster the pure dephasing is. The results show that using appropriate QD size at low temperature and using ultra-fast laser technology can effectively suppress pure dephasing due to exciton-LAP interaction.
We investigate the influence of phonon mediated interactions on the non-unitary evolution of geometrical phases in excitonic qubits formed in quantum dots entangled by pure Förster coupling. We consider decoherence to occur via acoustic phonons interacting through the deformation potential and piezoelectric coupling mechanisms. The influences of bath temperature, external electric field, quantum dot size and interdot distance on the evolution of geometrical phases are examined for the GaAs/AlGaAs material system. We extend the theory to determine the effect of dynamic decoupling employing ultrafast π-pulses on the evolution of geometrical phases in the presence of dephasing processes.
We have developed a full quantum microscopic theory to analyze the time evolution of transversal and longitudinal components of an exciton-single photon system coupled to bulk acoustic phonons. These components are subjected to two decay processes. One is radiative relaxation and the other is pure dephasing due to exciton-phonon interaction. The former results in a decay with an exponent linear to time, while the latter causes a faster initial decay than the radiative decay. We analyzed the dependence of the components on the duration of the input one-photon pulse, temperature, and radiative relaxation rates. Such a quantitative analysis is important for the developments of atom-photon interfaces which enable coherent transfer of quantum information between photons and atomic systems. We found that, for a GaAs spherical quantum dot in which the exciton interacts with bulk phonons, the maximal probability of the excited state can be increased up to 75%. This probability can be considered as the efficiency for quantum information transfer from photon to exciton.
We investigate phonon-assisted mechanisms which contribute to the decoherence of excitonic qubits in quantum dot systems coupled by a Förster-type transfer process. Using the Fermi Golden Rule, we derive explicit expressions for the relaxation and dephasing times for excitonic qubits interacting with acoustic phonons via both the deformation potential and piezoelectric coupling. The decoherence times computed using the Fermi Golden Rule are consistent with those estimated using Bloch–Redfield theory at interdot tunnelling energies small enough for Markovian theories to be valid. Our results show that renormalization of interdot tunnelling frequencies due to phonon interactions is influenced mainly by bias and lattice temperature in GaAs/AlGaAs quantum dot systems.
We present a study of the dephasing of an excitonic qubit trapped within a chain of two semiconductor quantum dots immersed in a bulk material. We consider a specific excitonic wave-function which spreads across the chain. The source of the dephasing is the phonon field of the bulk material interacting with the single exciton within the structure. We show that an excitonic wave function which extends over more than one quantum dot is remarkably more robust against the dephasing. The details of dephasing depends on the distance which separates the two quantum dots. In particular, as this distance increases, the residual coherence increases up to a maximum value. However, the short-time dephasing is shown to be characterised by the appearance of a transient behavior. The actual duration of this transient is determined by the separation between the dots.