Quantum Pseudodot Research Articles

The temperature dependence on the coherence time of a quantum pseudodot qubit

In this work, the energies and eigenfunctions of ground state and first-excited states (GFES) of a strongly coupled polaron in a quantum pseudo-dot (QPD) were studied by using variational method of Pekar type (VMPT). A single qubit can be realized in this two-level quantum system. Then, we calculated the coherence time of a QPD qubit by employing the Fermi Golden Rule. The temperature effects on the coherence time are taken into account by using the quantum statistics theory (QST) and self-consistent calculation method. According to the obtained results, it is found that the coherence time increases with decreasing temperature. Also, this time is a decaying function of the chemical potential of the two-dimensional electron gas and the zero point of the PHP.

Cumulative Effects of Laser and Spin–Orbit Interaction (SOI) on the Thermal Properties of Quantum Pseudo-dot

Cumulative Effects of Laser and Spin–Orbit Interaction (SOI) on the Thermal Properties of Quantum Pseudo-dot

Ground-state and excited-state energy of parabolic potential quantum pseudodot system

Using the variational method of the Pekar type, we studied the ground-state energy and the excited-state energy of a parabolic potential quantum pseudodot. Through numerical calculation and derivation, we found that (1) the ground-state energy E0 increases with the increase of V0; (2) when λ > 6, E0 and E1 are increasing functions of λ, but when λ < 5, E0 and E1 are decreasing functions of λ. In these processes, the change of ωc is not significant. (3) E1 is a decreasing function of l1 and l2.

Study of RbCl quantum pseudo-dot qubits using Shannon and Laplace entropies

In this work, an electron was considered which is coupled to the LO-phonon in RbCl quantum pseudo-dot. The Pekar variational method was used to calculate the eigenenergies and eigenfunctions of the ground and the first-excited states of the system. Two different entropies were considered, the Shannon and Laplace, to study decoherence of RbCl pseudodot qubit for different parameters. According to the obtained results, it is found that the entropy has the oscillatory periodic evolution as a function of the time due to the form of the confinement potential. It is also found that the entropies oscillate under a sinusoidal envelope with increasing the confinement parameters.

Periodicity of probability density and effects of Rashba Spin–orbit interaction on excitation energy of bound polaron in quantum pseudodot

Abstract We study the probability density and the excitation energy of the bound polaron in the quantum pseudodot under the Rashba spin–orbit interaction by using the unitary transformation of Lee–Low–Pines and the variational method of Pekar. The results of a numerical calculation show that the probability density of the bound polaron in the superposition state is periodic and oscillates with the period T 0 . Due to the Rashba spin–orbit interaction, the excitation energy splits into different branches. It also can be seen that the excitation energy changes with the phonon wave vector when the two-dimensional electron gas’s chemical potential, the electron–LO phonon coupling, the Coulomb bound potential and the Rashba coupling parameter take different values.

Study of RbCl quantum pseudodot qubits by using of non-extensive entropies

In this work, an electron which is strongly coupled to the strong electron–phonon (e–p) in RbCl quantum pseudodot qubit is considered. First, we employ the Pekar variational method and obtain the eigenenergies and eigenfunctions of the ground and the first excited states of the system. Then, we have employed three different entropies such as Tsallis, Landsberg–Vedral, and Escort for the system subjected to an applied electric field. In this regard, we have studied the effect of polaronic radius, electric field, e–p coupling strength, and non-extensive parameter. It is found that the entropies oscillate with passing time. The entropies increase with enhancing electric field, e–p coupling strength and decrease with polaronic radius. The results show that the missing information in the RbCl pseudodot qubit can be controlled by changing the system parameters. According to the results, it is deduced that the entropy is an important quantity to display the total storage or missing information in a qubit.

The Effects of Electric Field on the Coherence Time of RbCl Quantum Pseudodot Qubit

We academically explore the properties of the coherence time (CT) of an electron powerful coupled to the phonons in a RbCl quantum pseudodot (QPD) qubit with an exterior electric field alongside the ρx direction. By employing the Pekar type variational method (PTVM) and the Fermi golden rule, the CT changes with the electric field, the chemical potential of the two-dimensional electron gas (CPTDEG), the zero point of the pseudoharmonic potential (ZPPHP) and the polaron radius is studied. The examined results indicate ① that the CT of RbCl QPD qubit decays with aggrandizing electric field, ② that the CT is a decreasing function of the CPTDEG, the ZPPHP and the polaron radius, ③ that here we can find that we can adjust the CT by changing the external electric field, the CPTDEG, the ZPPHP and the polaron radius.

The magnetic field effect on the coherence time of qubit in RbCl crystal quantum pseudodot

In an external z-direction magnetic field, the coherence property of qubit in RbCl crystal quantum pseudodot (QPD) is discussed. The coherence time of QPD qubit is calculated by using the Pekar type variational method and the Fermi Golden Rule. It is analytically derived that the coherence time versus the cyclotron frequency of the magnetic field and the QPD parameters (the chemical potential of the two-dimensional electron gas, the zero point of pseudoharmonic potential, and the polaron radius) in QPD system. According to the results, it is found that the parameters and the magnetic field adjusts the coherence time of the qubit in the RbCl crystal QPD.

The Effect of Coulomb Impurity Potential on the Coherence Time of RbCl Quantum Pseudodot Qubit

We have considered the pseudoharmonic potential (PHP) for a RbCl quantum pseudodot (QPD) qubit with a hydrogen-like impurity at the center. By employing the Pekar variational method and the Fermi Golden Rule, we study the properties of the coherence time of an electron strongly interacting with longitudinal optical phonon in a RbCl QPD qubit. The coherence time changing with the Coulombic impurity potential strength, the two-dimensional chemical potential of the electron gas, the PHP zero point and the polaron radius is theoretically investigated. The obtained results indicate that ① the coherence time of RbCl QPD qubit decreases with increasing Coulombic impurity potential strength, ② the coherence time is a decaying function of the two-dimensional chemical potential of the electron gas and the PHP zero point, ③ the smaller the polaron radius is, the smaller the coherence time is.

Rashba effects on the first excited state of the bound polaron in a quantum pseudodot

By using the Lee-Low-Pines unitary transformation and the Pekar type variational method, we studied Rashba effects on the first excited state of the bound polarons in a quantum pseudodot. In the paper, we have derived the energy of the first excited state of the polaron, which is a function of the electron-LO phonon coupling strength, the wave vector, the constraint size, the chemical potential and the Coulomb bound potential. According to the theoretical analysis, we get the following conclusions: The first excited state energy increases with the wave vector and the chemical potential increasing, and decreases with the increase of the electron-LO phonon coupling strength and the constraint size rising. And when the condition is different, the law of change of the first excited state energy of the polaron with the Coulomb bound potential is different. Under the influence of the Rashba spin-orbit interaction, the first excited state energy splits into different branches. Relatively, the Rashba effect is obviously affected by the constraint size.

Influences of temperature and Rashba spin-orbit interaction on oscillation period of bound polaron in quantum pseudodot

In the present work, we study the influences of the temperature and the Rashba spin-orbit interaction on the oscillation period of the bound polaron in the quantum pseudodot using the Lee-Low-Pines unitary transformation, the variational method of Pekar-type and the quantum statistical theory. We have derived the oscillation period of the bound polaron in the superposition state and reported the temperature dependences and the Rashba spin-orbit interaction effects of the oscillation period of polaron when the wave vector, the electron-LO phonon coupling, the Coulomb bound potential and the chemical potential take different values.

Temperature Effects on the First Excited State of the Polaron in an Asymmetric Quantum Pseudodot Under Magnetic Field

Using the variational method of the Pekar type, we investigate the first excited state energy of the polaron in an asymmetric quantum pseudodot under the magnetic field. Temperature effects on the polaron are calculated by employing the quantum statistical theory, and the influences of the chemical potential, the zero point of pseudo-harmonic potential (PHP), the cyclotron frequency, the electron–phonon coupling strength and the transverse and the longitudinal effective confinement lengths are taken into account. The results show that the first excited state energy decreases (increases) when the temperature is increased at lower (higher) temperature region. And it is an increasing function of the chemical potential, the zero point of PHP, the cyclotron frequency and the electron–phonon coupling strength. Simultaneously, it is a decreasing one of the transverse and the longitudinal effective confinement lengths.

Effect of hydrogen-like impurity on a qubit in quantum pseudodot at finite temperature

Influences of temperature on the qubit's properties in a quantum pseudodot (QPD) are studied by using the variational method of Pekar type (VMPT) and quantum statistics theory (QST). The formation of qubit requires two special conditions: One is the strong-coupling between the electron and the bulk longitudinal optical (LO) phonon, and the other is the hydrogen-like impurity (HLI) locating at the center of the QPD. So, we choose strong-coupling RbCl crystal as an example and calculate the electron probability density (EPD) and the oscillating period (OP) of the QPD qubit changing with the temperature and the Coulombic impurity potential (CIP).

The ground-state lifetime of polaron in a two-dimensional quantum pseudodot system

We study the ground-state lifetime (GSL) of polaron in a two-dimensional RbCl quantum pseudodot (QPD) system by using a variational method of Pekar type (PTVM) and the quantum statistical theory. Considering the polaron effect, we derive the dependent relations of the temperature, the electric field, the chemical potential (CP) of the two-dimensional electron gas (TDEG), the polaron radius (PR) and the zero point (ZP) of the pseudoharmonic potential (PHP) on the GSL of polaron. The calculated results show that the GSL $$\tau$$ of polaron will decrease when the CP $$V_{0}$$ of the TDEG, the electric field and the PR $$R_{p}$$ increase, but will increase while the ZP $$r_{0}$$ of the PHP, the ground-state energy (GSE) and the temperature parameter $$\gamma$$ become larger, respectively. That means that by changing the electric field, the temperature, the PR, the CP of the TDEG and the ZP of the PHP, one can adjust the GSL of polaron, which may offer new insight into studying many related applications in quantum computation (QC) and control of electron transition.

Application of entropies to the study of the decoherence of magnetopolaron in 0-D nanosystem

Many methods have been experimented to study decoherence in quantum dot (QD). Tsallis, Shannon and Gaussian entropy have been used to study decoherence separately; in this paper, we compared the results of the Gaussian, Shannon, and Tsallis entropies in 0-D nanosystem. The linear combination operator and the unitary transformation was used to derive the magnetopolaron spectrum that strongly interacts with the LO phonons in the presence of an electric field in the pseudoharmonic and delta quantum dot. Numerical results revealed for the quantum pseudo dot that: (i) the amplitude of Gauss entropy is greater than the amplitude of Tsallis entropy which in turn is greater than the amplitude of Shannon entropy. The Tsallis entropy is not more significant in nanosystem compared to Shannon and Gauss entropies, (ii) with an increase of the zero point, the dominance of the Gauss entropy on the Shannon entropy was observed on one hand and the dominance of the Shannon entropy on the Tsallis entropy on the other hand; this suggested that in nanosystem, Gauss entropy is more suitable in the evaluation of the average of information in the system, for the delta quantum dot it was observed that (iii) when the Gauss entropy is considered, a lot of information about the system is missed. The collapse revival phenomenon in Shannon entropy was observed in RbCl and GaAs delta quantum dot with the enhancement of delta parameter; with an increase in this parameter, the system in the case of CsI evolved coherently; with Shannon and Tsallis entropies, information in the system is faster and coherently exchanged; (iv) the Shannon entropy is more significant because its amplitude outweighs the others when the delta dimension length enhances. The Tsallis entropy involves as wave bundle; which oscillate periodically with an increase of the oscillation period when delta dimension length is improved.

Influences of the Temperature on the Ground State of the Coupling Polaron in an Asymmetric Quantum Pseudodot Under the External Magnetic Field

We studied that the influences of the temperature on the ground state energy of the coupling polaron in an asymmetric quantum pseudodot (QPD) under the external magnetic field by using the quantum statistical theory (QST) and the variational method of the Pekar-type (VMPT). And the relations between the ground state energy and the external magnetic field, the chemical potential of the two-dimensional electron gas, the pseudoharmonic potential (PHP) zero point, the coupling strength and the effective confinement lengths are discussed. The results of our study have shown that the ground state energy firstly declines and then rises as the temperature is increased from a low value. We also find that the ground state energy rises with the enhancing external magnetic field and the chemical potential of the two-dimensional electron gas. And the ground state energy declines firstly and then reinforces as the PHP zero point is enhanced. What’s more, the ground state energy is reductive function of the coupling strength and the effective confinement lengths.

Constructiveness and destructiveness of temperature in asymmetric quantum pseudo dot qubit system

By using the variational method of the Pekar type, we theoretically study the temperature effects on the asymmetric quantum pseudo dot qubit with a pseudoharmonic potential under an electromagnetic field. The numerical results are analyzed and discussed in detail and show that the relationships of the ground and first excited state energies, the electron oscillation period and the electron probability density in the superposition state of the ground state and the first-excited state with the temperature, the chemical potential, the pseudoharmonic potential, the electric field strength, the cyclotron frequency, the electron phonon coupling constant, the transverse and longitudinal effective confinement length, respectively.

Temperature effects of the electron probability density on quantum pseudodot qubit

With variational method of Pekar type and quantum statistics theory, the temperature effects on electron probability density (EPD) of a strongly-coupling electron-LO-phonon (polaron) in RbCl material quantum pseudodots (QPDs) are studied. The qubit in the QPD system can be built by the two-level energy states. The EPD periodically oscillates in the special material QPD with a certain period as the electron is located in the superposition state of the ground and first excited states. The changing functions of EPD and the oscillating period with the system temperature and the chemical potential of the two-dimensional electron gas are found.

Electromagnetically induced transparency in a quantum pseudo-dot with spin–orbit interaction

Electromagnetically induced transparency of a quantum pseudo-dot with Rashba spin–orbit interaction and under the influence of external magnetic field is investigated. To study electromagnetically induced transparency the dependence of absorption coefficient and refractive index of the probe light pulse on the Rashba spin–orbit interaction strength, magnetic field, dot size and parameters of pseudo-harmonic potential is explained. Results show the considerable effects of SOI and other mentioned parameters on the electromagnetically induced transparency of the system.

Temperature effect of a quantum pseudodot qubit

Considering a variational method of the Pekar type and the quantum statistics theory, the temperature effects on the probability density and the oscillating frequency of an electron-LO-phonon strongly coupling in a RbCl quantum pseudodot (QPD) are investigated. It is discovered that a qubit may be made up of a QPD two-level-system. Furthermore, when an electron locates in the superposition state of the ground and first excited states, the electron's probability density varies periodically with time and oscillates in the RbCl QPD with an independent period. The electron's probability density increases (decreases) with increasing temperature at low (high) temperature. At low (high) temperature, the oscillating frequency decreases (increases) with an increase of the temperature, the chemical potential of the two-dimensional electron gas and the zero point of the pseudoharmonic potential. The oscillating frequency is a decreasing function of the polaron radius.