This paper explores a double quantum images representation(DNEQR)model that allows for simultaneous storage of two digital images in a quantum superposition state.Additionally,a new type of two-dimensional hyperchaoti...This paper explores a double quantum images representation(DNEQR)model that allows for simultaneous storage of two digital images in a quantum superposition state.Additionally,a new type of two-dimensional hyperchaotic system based on sine and logistic maps is investigated,offering a wider parameter space and better chaotic behavior compared to the sine and logistic maps.Based on the DNEQR model and the hyperchaotic system,a double quantum images encryption algorithm is proposed.Firstly,two classical plaintext images are transformed into quantum states using the DNEQR model.Then,the proposed hyperchaotic system is employed to iteratively generate pseudo-random sequences.These chaotic sequences are utilized to perform pixel value and position operations on the quantum image,resulting in changes to both pixel values and positions.Finally,the ciphertext image can be obtained by qubit-level diffusion using two XOR operations between the position-permutated image and the pseudo-random sequences.The corresponding quantum circuits are also given.Experimental results demonstrate that the proposed scheme ensures the security of the images during transmission,improves the encryption efficiency,and enhances anti-interference and anti-attack capabilities.展开更多
A viable strategy for enhancing photovoltaic performance is to comprehend the underlying quantum physical regime of charge transfer in a double quantum dots(DQD) photocell. This work explored the photovoltaic performa...A viable strategy for enhancing photovoltaic performance is to comprehend the underlying quantum physical regime of charge transfer in a double quantum dots(DQD) photocell. This work explored the photovoltaic performance dependent spatially correlated fluctuation in a DQD photocell. The effects of spatially correlated fluctuation on charge transfer and output photovoltaic efficiency were explored in a proposed DQD photocell model. The results revealed that the charge transport process and the time to peak photovoltaic efficiency were both significantly delayed by the spatially correlated fluctuation, while the anti-spatially correlated fluctuation reduced the output peak photovoltaic efficiency. Further results revealed that the delayed response could be suppressed by gap difference and tunneling coefficient within two dots. Subsequent investigation demonstrated that the delayed response was caused by the spatial correlation fluctuation slowing the generative process of noise-induced coherence, which had previously been proven to improve the quantum photovoltaic performance in quantum photocells. And the reduced photovoltaic properties were verified by the damaged noise-induced coherence owing to the anti-spatial correlation fluctuation and a hotter thermal ambient environment. The discovery of delayed response generated by the spatially correlated fluctuations will deepen the understanding of quantum features of electron transfer, as well as promises to take our understanding even further concerning quantum techniques for high efficiency DQD solar cells.展开更多
The binding energy of a hydrogenic impurity in self-assembled double quantum dots is calculated via the finitedifference method. The variation in binding energy with donor position, structure parameters and external m...The binding energy of a hydrogenic impurity in self-assembled double quantum dots is calculated via the finitedifference method. The variation in binding energy with donor position, structure parameters and external magnetic field is studied in detail. The results found are: (i) the binding energy has a complex behaviour due to coupling between the two dots; (ii) the binding energy is much larger when the donor is placed in the centre of one dot than in other positions; and (iii) the external magnetic field has different effects on the binding energy for different quantum-dot sizes or lateral confinements.展开更多
The effects of optical field on the phenomenon of optical bistability(OB) are investigated in a K-type semiconductor double quantum well(SDQW) under various parametric conditions. It is shown that the OB threshold can...The effects of optical field on the phenomenon of optical bistability(OB) are investigated in a K-type semiconductor double quantum well(SDQW) under various parametric conditions. It is shown that the OB threshold can be manipulated by increasing the intensity of coupling field. The dependence of the shift of OB hysteresis curve on probe wavelength detuning is then explored. In order to demonstrate controllability of the OB in this SDQW, we compare the OB features of three different configurations which could arise in this SDQW scheme, i.e., K-type, Y-type, and inverted Y-type systems. The controllability of this semiconductor nanostructure medium makes the presented OB scheme more valuable for applications in all-optical switches, information storage, and logic circuits of all optical information processing.展开更多
Using the Keldysh nonequilibrium Green function and equation-of-motion technique, this paper studies the mag- netotransport through an Aharonov-Bohm (AB) ring with parallel double quantum dots coupled to ferromagnet...Using the Keldysh nonequilibrium Green function and equation-of-motion technique, this paper studies the mag- netotransport through an Aharonov-Bohm (AB) ring with parallel double quantum dots coupled to ferromagnetic leads. It calculates the transmission probability in both the equilibrium and the nonequilibrium case, analyses the conduc- tance and the tunnel magnetoresistance for various parameters, and obtains some new results. These results show that this system is provided with an excellent spin filtering property, and that a large tunnelling magnetoresistance and a negative tunnelling magnetoresistance can arise by adjusting relative parameters; these facts indicate that this system is a possible candidate for spin valve transistors, and has important applications in spintronics.展开更多
Using the innovative method of the additional Bloch vector,the electron transfer properties of a double quantum dot(DQD) system measured by a quantum point contact(QPC) in a fluctuating environment are investigated.Th...Using the innovative method of the additional Bloch vector,the electron transfer properties of a double quantum dot(DQD) system measured by a quantum point contact(QPC) in a fluctuating environment are investigated.The results show that the environmental noises in transverse and longitudinal directions play different roles in the dynamical evolution of the open quantum systems.Considering the DQD with symmetric energy level,the Fano factor exhibits a slight peak with the increase of transverse noise amplitude σ_(T),which provides a basis for distinguishing dynamical phenomena caused by different directional fluctuation noises in symmetric DQD structures by studying the detector output.In the case of asymmetric DQD,the dependence of a detector current involving the level displacement is distinct when increasing the transverse noise damping coefficient τ_(T) and the longitudinal noise damping coefficient τ_(ε) respectively.Meanwhile,the transverse noise damping coefficient τ_(T) could significantly reduce the Fano factor and enhance the stability of the quantum system compared with the longitudinal one.The Fano factors with stable values as the enhancement of noise amplitudes show different external influences from the detector measurement,and provide a numerical reference for adjusting the noise amplitudes in both transverse and longitudinal directions appropriately in a microscopic experimental process to offset the decoherence effect caused by the measurements.Finally,the research of average waiting time provides unique insights to the development of single electron transfer theory in the short-time limit.展开更多
We analyze the transport through asymmetric double quantum dots with an inhomogeneous Zeeman splitting in the presence of crossed dc and ac magnetic fields. A strong spin-polarized current can be obtained by changing ...We analyze the transport through asymmetric double quantum dots with an inhomogeneous Zeeman splitting in the presence of crossed dc and ac magnetic fields. A strong spin-polarized current can be obtained by changing the dc magnetic field. It is mainly due to the resonant tunnelling. But for the ferromagnetic right electrode, the electron spin resonance also plays an important role in transport. We show that the double quantum dots with three-level mixing under crossed dc and ac magnetic fields can act not only as a bipolar spin filter but also as a spin inverter under suitable conditions.展开更多
By means of the modal expansion method with an R-matrix propagation algorithm, effects of the coupling between resonance photonic states on the resonance tunneling through a double quantum well structure are investiga...By means of the modal expansion method with an R-matrix propagation algorithm, effects of the coupling between resonance photonic states on the resonance tunneling through a double quantum well structure are investigated. We examine the effects on the transmission spectra due to variation of the second well width and middle barrier thickness. Drastic change of the tunneling spectra is found and analyzed when the wells are filled with left-hand media.展开更多
We investigate the spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the density of states in ...We investigate the spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the density of states in the Kondo regime for two different configurations of the leads. It is found that the transport shows some remarkable properties depending on the spin-flip strength. These effects may be useful in exploiting the role of electronic correlation in spintronics.展开更多
We present a phase-and spin-dependent manipulation of leakage of a Majorana mode into a double quantum dot.We study the density of states(DOS)to show the effect of phase change factor on the Majorana leakage into(out)...We present a phase-and spin-dependent manipulation of leakage of a Majorana mode into a double quantum dot.We study the density of states(DOS)to show the effect of phase change factor on the Majorana leakage into(out)of a double quantum dot.The DOS is derived from the Green's function of the quantum dot by the equation of motion method,and exhibits a formant structure whenφ=0,2πand a resonance shape whenφ=0.5πand 1.5π.Also,it changes more strongly under the spin-polarized coefficient than the non-polarized lead.Such a theoretical model can be modified to explore the spin-dependent effect in the hybrid Majorana quantum dot system.展开更多
We study shot noise in tunneling current through a double quantum dot connected to two electric leads. We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dyn...We study shot noise in tunneling current through a double quantum dot connected to two electric leads. We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dynamics. The approach based on the occupation-state basis, despite being widely used in many previous studies, is valid only when the interdot coupling strength is much smaller than the energy difference between the two dots. In contrast, the calculations using the eigenstate basis are valid for an arbitrary interdot coupling. Using realistic model parameters, we demonstrate that the predicted currents and shot-noise properties from the two approaches are significantly different when the interdot coupling is not small. Furthermore, properties of the shot noise predicted using the eigenstate basis successfully reproduce qualitative features found in a recent experiment.展开更多
We study the thermoelectric transport through a double-quantum-dot system with spin-dependent interdot cou- pling and ferromagnetic electrodes by means of the non-equilibrium Green's function in the linear response r...We study the thermoelectric transport through a double-quantum-dot system with spin-dependent interdot cou- pling and ferromagnetic electrodes by means of the non-equilibrium Green's function in the linear response regime. It is found that the thermoelectric coefficients are strongly dependent on the splitting of the interdot coupling, the relative magnetic configurations, and the spin polarization of leads. In particular, the thermoelectric efficiency can reach a considerable value in the parallel configuration when the effective interdot coupling and the tunnel coupling between the quantum dots and the leads for the spin-down electrons are small. Moreover, the thermoelectric efficiency increases with the intradot Coulomb interaction increasing and can reach very high values at appropriate temperatures. In the presence of the magnetic field, the spin accumulation in the leads strongly suppresses the thermoelectric efficiency, and a pure spin thermopower can be obtained.展开更多
We implement a quantum walk in phase space with a new mechanism based on the superconducting resonator-assisted double quantum dots. By analyzing the hybrid system, we obtain the necessary factors implementing a quant...We implement a quantum walk in phase space with a new mechanism based on the superconducting resonator-assisted double quantum dots. By analyzing the hybrid system, we obtain the necessary factors implementing a quantum walk in phase space: the walker, coin, coin flipping and conditional phase shift. The coin flipping is implemented by adding a driving field to the resonator. The interaction between the quantum dots and resonator is used to implement conditional phase shift. Furthermore, we show that with different driving fields the quantum walk in phase space exhibits a ballistic behavior over 25 steps and numerically analyze the factors influencing the spreading of the walker in phase space.展开更多
A parallel-coupled double quantum dot (PCDQD) system with two multi-quantum dot chains is designed. Conductance versus Fermi energy level is investigated utilizing the non-equilibrium Green's function approach. If ...A parallel-coupled double quantum dot (PCDQD) system with two multi-quantum dot chains is designed. Conductance versus Fermi energy level is investigated utilizing the non-equilibrium Green's function approach. If two quantum dots are added on each side of the PCDQD system, additional Breit Wigner and Fano resonances occur in the conductance spectra. If quantum dots are added on one side of the system, small Fano resonances can be observed in the conductance spectra. Adjusting the number of side-coupled quantum dots, the anti-resonance bands emerge at different positions, which makes the system applicable as a quantum switching device. Moreover, the I-V characteristic curve presents the step characteristic and the width of the step decreases with increasing the number of side-coupled quantum dots.展开更多
The 810-nm InGaAlAs/AlGaAs double quantum well (QW) semiconductor lasers with asymmetric waveguide structures, grown by molecular beam epitaxy, show high quantum efficiency and high-power conver- sion efficiency at ...The 810-nm InGaAlAs/AlGaAs double quantum well (QW) semiconductor lasers with asymmetric waveguide structures, grown by molecular beam epitaxy, show high quantum efficiency and high-power conver- sion efficiency at continuous-wave (CW) power output. The threshold current density and slope efficiency of the device are 180 A/cm^2 and 1.3 W/A, respectively. The internal loss and the internal quantum efficiency are 1.7 cm^-1 and 93%, respectively. The 70% maximum power conversion efficiency is achieved with narrow far-field patterns.展开更多
In this paper the binding energy of the shallow.donor in CdTe/ZnTe strained double quantum well was calculated.The effect of the finite well potential and strain,resulting from the lattice mismatch,on the binding ener...In this paper the binding energy of the shallow.donor in CdTe/ZnTe strained double quantum well was calculated.The effect of the finite well potential and strain,resulting from the lattice mismatch,on the binding energy of the impurity is included in a variational framework.The binding energy is obtained as a function of the well width,barrier width,and impurity position in the barrier by using a variational method.The result of the present calculation shows that the variational law of the binding energy is similar to that of unstrained materials.展开更多
A new model of metal/semiconductor/metal double-quantum-ring connected in series is proposed and the transport properties in this model are theoretically studied. The results imply that the transmission coefficient sh...A new model of metal/semiconductor/metal double-quantum-ring connected in series is proposed and the transport properties in this model are theoretically studied. The results imply that the transmission coefficient shows periodic variations with increasing semiconductor ring size. The effects of the magnetic field and Rashba spin-orbit interaction on the transmission coefficient for two kinds of spin state electrons are different. The number of the transmission coefficient peaks is related to the length ratio between the upper arm and the half circumference of the ring. In addition, the transmission coefficient shows oscillation behavior with enhanced external magnetic field, and the corresponding average value is related to the two leads' relative position.展开更多
Let H be a finite Hopf C^* -algebra and H′be its dual Hopf algebra. Drinfeld's quantum double D(H) of H is a Hopf^*-algebra. There is a faithful positive linear functional θ on D(H). Through the associated Ge...Let H be a finite Hopf C^* -algebra and H′be its dual Hopf algebra. Drinfeld's quantum double D(H) of H is a Hopf^*-algebra. There is a faithful positive linear functional θ on D(H). Through the associated Gelfand-Naimark-Segal (GNS) representation, D(H) has a faithful^* -representation so that it becomes a Hopf C^* -algebra. The canonical embedding map of H into D(H) is isometric.展开更多
For a field k and two finite groups G and X, when G acts on X from the right by group automorphisms, there is a Hopf algebra structure on k-space (kX°P)* kG (see Theorem 2.1), called a non-balanced quantum ...For a field k and two finite groups G and X, when G acts on X from the right by group automorphisms, there is a Hopf algebra structure on k-space (kX°P)* kG (see Theorem 2.1), called a non-balanced quantum double and denoted by Dx(G). In this paper, some Hopf algebra properties of Dx (G) are given, the representation types of Dx (G) viewed as a k-algebra are discussed, the algebra structure and module category over Dx(G) are studied. Since the Hopf algebra structure of non-balanced quantum double DX (G) generMizes the usual quantum double D(G) for a finite group G, all results about Dx(G) in this paper can also be used to describe D(G) as a special case and the universal R-matrix of Dx (G) provides more solutions of Yang-Baxter equation.展开更多
The differential cross-section for electronic Raman scattering in double semi-parabolic quantum wells of typical GaAs/AlxGa1-xAs is investigated numerically with the effective-mass approximation. The dependence of the...The differential cross-section for electronic Raman scattering in double semi-parabolic quantum wells of typical GaAs/AlxGa1-xAs is investigated numerically with the effective-mass approximation. The dependence of the differential cross-section on structural parameters such as the barrier width and the well widths is studied. Our results indicate that the electronic Raman scattering is affected by the geometrical size and can be negligible in the symmetric double-well case.展开更多
基金Project supported by the Open Fund of Anhui Key Laboratory of Mine Intelligent Equipment and Technology (Grant No.ZKSYS202204)the Talent Introduction Fund of Anhui University of Science and Technology (Grant No.2021yjrc34)the Scientific Research Fund of Anhui Provincial Education Department (Grant No.KJ2020A0301)。
文摘This paper explores a double quantum images representation(DNEQR)model that allows for simultaneous storage of two digital images in a quantum superposition state.Additionally,a new type of two-dimensional hyperchaotic system based on sine and logistic maps is investigated,offering a wider parameter space and better chaotic behavior compared to the sine and logistic maps.Based on the DNEQR model and the hyperchaotic system,a double quantum images encryption algorithm is proposed.Firstly,two classical plaintext images are transformed into quantum states using the DNEQR model.Then,the proposed hyperchaotic system is employed to iteratively generate pseudo-random sequences.These chaotic sequences are utilized to perform pixel value and position operations on the quantum image,resulting in changes to both pixel values and positions.Finally,the ciphertext image can be obtained by qubit-level diffusion using two XOR operations between the position-permutated image and the pseudo-random sequences.The corresponding quantum circuits are also given.Experimental results demonstrate that the proposed scheme ensures the security of the images during transmission,improves the encryption efficiency,and enhances anti-interference and anti-attack capabilities.
基金the National Natural Science Foundation of China (Grant Nos. 62065009 and 61565008)Yunnan Fundamental Research Projects, China (Grant No. 2016FB009)。
文摘A viable strategy for enhancing photovoltaic performance is to comprehend the underlying quantum physical regime of charge transfer in a double quantum dots(DQD) photocell. This work explored the photovoltaic performance dependent spatially correlated fluctuation in a DQD photocell. The effects of spatially correlated fluctuation on charge transfer and output photovoltaic efficiency were explored in a proposed DQD photocell model. The results revealed that the charge transport process and the time to peak photovoltaic efficiency were both significantly delayed by the spatially correlated fluctuation, while the anti-spatially correlated fluctuation reduced the output peak photovoltaic efficiency. Further results revealed that the delayed response could be suppressed by gap difference and tunneling coefficient within two dots. Subsequent investigation demonstrated that the delayed response was caused by the spatial correlation fluctuation slowing the generative process of noise-induced coherence, which had previously been proven to improve the quantum photovoltaic performance in quantum photocells. And the reduced photovoltaic properties were verified by the damaged noise-induced coherence owing to the anti-spatial correlation fluctuation and a hotter thermal ambient environment. The discovery of delayed response generated by the spatially correlated fluctuations will deepen the understanding of quantum features of electron transfer, as well as promises to take our understanding even further concerning quantum techniques for high efficiency DQD solar cells.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10674040)the Natural Science Foundation of Hebei Province of China (Grant No. A2011205092)the Scientific and Technological Research and Development Projects of Handan City (Grant No. 1128120063-3)
文摘The binding energy of a hydrogenic impurity in self-assembled double quantum dots is calculated via the finitedifference method. The variation in binding energy with donor position, structure parameters and external magnetic field is studied in detail. The results found are: (i) the binding energy has a complex behaviour due to coupling between the two dots; (ii) the binding energy is much larger when the donor is placed in the centre of one dot than in other positions; and (iii) the external magnetic field has different effects on the binding energy for different quantum-dot sizes or lateral confinements.
基金supported by the Lithuanian Research Council(Grant No.VP1-3.1-M-01-V-03-001)
文摘The effects of optical field on the phenomenon of optical bistability(OB) are investigated in a K-type semiconductor double quantum well(SDQW) under various parametric conditions. It is shown that the OB threshold can be manipulated by increasing the intensity of coupling field. The dependence of the shift of OB hysteresis curve on probe wavelength detuning is then explored. In order to demonstrate controllability of the OB in this SDQW, we compare the OB features of three different configurations which could arise in this SDQW scheme, i.e., K-type, Y-type, and inverted Y-type systems. The controllability of this semiconductor nanostructure medium makes the presented OB scheme more valuable for applications in all-optical switches, information storage, and logic circuits of all optical information processing.
基金Project supported by the Scientific Research Fund of the Education Department of Sichuan Province of China (Grant No. 2006A069)Funds for Major Basic Research Project of Sichuan Province of China (Grant No. 2006J13-155)
文摘Using the Keldysh nonequilibrium Green function and equation-of-motion technique, this paper studies the mag- netotransport through an Aharonov-Bohm (AB) ring with parallel double quantum dots coupled to ferromagnetic leads. It calculates the transmission probability in both the equilibrium and the nonequilibrium case, analyses the conduc- tance and the tunnel magnetoresistance for various parameters, and obtains some new results. These results show that this system is provided with an excellent spin filtering property, and that a large tunnelling magnetoresistance and a negative tunnelling magnetoresistance can arise by adjusting relative parameters; these facts indicate that this system is a possible candidate for spin valve transistors, and has important applications in spintronics.
基金Project supported by the Natural Science Foundation of Shandong Province,China(Grant No.ZR2014AM030)。
文摘Using the innovative method of the additional Bloch vector,the electron transfer properties of a double quantum dot(DQD) system measured by a quantum point contact(QPC) in a fluctuating environment are investigated.The results show that the environmental noises in transverse and longitudinal directions play different roles in the dynamical evolution of the open quantum systems.Considering the DQD with symmetric energy level,the Fano factor exhibits a slight peak with the increase of transverse noise amplitude σ_(T),which provides a basis for distinguishing dynamical phenomena caused by different directional fluctuation noises in symmetric DQD structures by studying the detector output.In the case of asymmetric DQD,the dependence of a detector current involving the level displacement is distinct when increasing the transverse noise damping coefficient τ_(T) and the longitudinal noise damping coefficient τ_(ε) respectively.Meanwhile,the transverse noise damping coefficient τ_(T) could significantly reduce the Fano factor and enhance the stability of the quantum system compared with the longitudinal one.The Fano factors with stable values as the enhancement of noise amplitudes show different external influences from the detector measurement,and provide a numerical reference for adjusting the noise amplitudes in both transverse and longitudinal directions appropriately in a microscopic experimental process to offset the decoherence effect caused by the measurements.Finally,the research of average waiting time provides unique insights to the development of single electron transfer theory in the short-time limit.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10874020 and 11174042)the National Basic Research Program of China (Grants No. 2011CB922204)+1 种基金the CAEP,China (Grant No. 2011B0102024)the SRF for ROCS,SEM,China
文摘We analyze the transport through asymmetric double quantum dots with an inhomogeneous Zeeman splitting in the presence of crossed dc and ac magnetic fields. A strong spin-polarized current can be obtained by changing the dc magnetic field. It is mainly due to the resonant tunnelling. But for the ferromagnetic right electrode, the electron spin resonance also plays an important role in transport. We show that the double quantum dots with three-level mixing under crossed dc and ac magnetic fields can act not only as a bipolar spin filter but also as a spin inverter under suitable conditions.
基金Project supported by the National Natural Science Foundation of China (Grant No 10775091)
文摘By means of the modal expansion method with an R-matrix propagation algorithm, effects of the coupling between resonance photonic states on the resonance tunneling through a double quantum well structure are investigated. We examine the effects on the transmission spectra due to variation of the second well width and middle barrier thickness. Drastic change of the tunneling spectra is found and analyzed when the wells are filled with left-hand media.
基金Project supported by Scientific Research Fund of Sichuan Provincial Education Department of China (Grant No 2006A069)Funds for Major Basic Research Project of Sichuan Province, China (Grant No 2006J13-155)
文摘We investigate the spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the density of states in the Kondo regime for two different configurations of the leads. It is found that the transport shows some remarkable properties depending on the spin-flip strength. These effects may be useful in exploiting the role of electronic correlation in spintronics.
基金the Science Foundation of Civil Aviation Flight University of China(Grant No.JG2019-19)。
文摘We present a phase-and spin-dependent manipulation of leakage of a Majorana mode into a double quantum dot.We study the density of states(DOS)to show the effect of phase change factor on the Majorana leakage into(out)of a double quantum dot.The DOS is derived from the Green's function of the quantum dot by the equation of motion method,and exhibits a formant structure whenφ=0,2πand a resonance shape whenφ=0.5πand 1.5π.Also,it changes more strongly under the spin-polarized coefficient than the non-polarized lead.Such a theoretical model can be modified to explore the spin-dependent effect in the hybrid Majorana quantum dot system.
基金Project supported by the National Basic Research Program of China (Grant Nos. 2009CB929300 and 2006CB921205)the National Natural Science Foundation of China (Grant Nos. 10534060 and 0625416)the Research Grant Council of Hong Kong SAR project (Grant No. 500908)
文摘We study shot noise in tunneling current through a double quantum dot connected to two electric leads. We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dynamics. The approach based on the occupation-state basis, despite being widely used in many previous studies, is valid only when the interdot coupling strength is much smaller than the energy difference between the two dots. In contrast, the calculations using the eigenstate basis are valid for an arbitrary interdot coupling. Using realistic model parameters, we demonstrate that the predicted currents and shot-noise properties from the two approaches are significantly different when the interdot coupling is not small. Furthermore, properties of the shot noise predicted using the eigenstate basis successfully reproduce qualitative features found in a recent experiment.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11274208,10974124,and 11004124)the Shanxi Natural Science Foundation,China (Grant No. 2009011001-1)
文摘We study the thermoelectric transport through a double-quantum-dot system with spin-dependent interdot cou- pling and ferromagnetic electrodes by means of the non-equilibrium Green's function in the linear response regime. It is found that the thermoelectric coefficients are strongly dependent on the splitting of the interdot coupling, the relative magnetic configurations, and the spin polarization of leads. In particular, the thermoelectric efficiency can reach a considerable value in the parallel configuration when the effective interdot coupling and the tunnel coupling between the quantum dots and the leads for the spin-down electrons are small. Moreover, the thermoelectric efficiency increases with the intradot Coulomb interaction increasing and can reach very high values at appropriate temperatures. In the presence of the magnetic field, the spin accumulation in the leads strongly suppresses the thermoelectric efficiency, and a pure spin thermopower can be obtained.
基金Project supported by the National Natural Science Foundation of China(Grant No.11474049)CAST Innovation Fund
文摘We implement a quantum walk in phase space with a new mechanism based on the superconducting resonator-assisted double quantum dots. By analyzing the hybrid system, we obtain the necessary factors implementing a quantum walk in phase space: the walker, coin, coin flipping and conditional phase shift. The coin flipping is implemented by adding a driving field to the resonator. The interaction between the quantum dots and resonator is used to implement conditional phase shift. Furthermore, we show that with different driving fields the quantum walk in phase space exhibits a ballistic behavior over 25 steps and numerically analyze the factors influencing the spreading of the walker in phase space.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11447132 and 11504042the Chongqing Science and Technology Commission Project under Grant Nos cstc2014jcyj A00032 and cstc2016jcyj A1158the Scientific Research Project for Advanced Talents of Yangtze Normal University under Grant No 2017KYQD09
文摘A parallel-coupled double quantum dot (PCDQD) system with two multi-quantum dot chains is designed. Conductance versus Fermi energy level is investigated utilizing the non-equilibrium Green's function approach. If two quantum dots are added on each side of the PCDQD system, additional Breit Wigner and Fano resonances occur in the conductance spectra. If quantum dots are added on one side of the system, small Fano resonances can be observed in the conductance spectra. Adjusting the number of side-coupled quantum dots, the anti-resonance bands emerge at different positions, which makes the system applicable as a quantum switching device. Moreover, the I-V characteristic curve presents the step characteristic and the width of the step decreases with increasing the number of side-coupled quantum dots.
文摘The 810-nm InGaAlAs/AlGaAs double quantum well (QW) semiconductor lasers with asymmetric waveguide structures, grown by molecular beam epitaxy, show high quantum efficiency and high-power conver- sion efficiency at continuous-wave (CW) power output. The threshold current density and slope efficiency of the device are 180 A/cm^2 and 1.3 W/A, respectively. The internal loss and the internal quantum efficiency are 1.7 cm^-1 and 93%, respectively. The 70% maximum power conversion efficiency is achieved with narrow far-field patterns.
文摘In this paper the binding energy of the shallow.donor in CdTe/ZnTe strained double quantum well was calculated.The effect of the finite well potential and strain,resulting from the lattice mismatch,on the binding energy of the impurity is included in a variational framework.The binding energy is obtained as a function of the well width,barrier width,and impurity position in the barrier by using a variational method.The result of the present calculation shows that the variational law of the binding energy is similar to that of unstrained materials.
基金Project supported by the Natural Foundation of the Bureau of Education of Hebei Province,China(No.Z2008103)
文摘A new model of metal/semiconductor/metal double-quantum-ring connected in series is proposed and the transport properties in this model are theoretically studied. The results imply that the transmission coefficient shows periodic variations with increasing semiconductor ring size. The effects of the magnetic field and Rashba spin-orbit interaction on the transmission coefficient for two kinds of spin state electrons are different. The number of the transmission coefficient peaks is related to the length ratio between the upper arm and the half circumference of the ring. In addition, the transmission coefficient shows oscillation behavior with enhanced external magnetic field, and the corresponding average value is related to the two leads' relative position.
文摘Let H be a finite Hopf C^* -algebra and H′be its dual Hopf algebra. Drinfeld's quantum double D(H) of H is a Hopf^*-algebra. There is a faithful positive linear functional θ on D(H). Through the associated Gelfand-Naimark-Segal (GNS) representation, D(H) has a faithful^* -representation so that it becomes a Hopf C^* -algebra. The canonical embedding map of H into D(H) is isometric.
基金Supported by Doctoral Foundation of Qingdao University of Science and Technology (20080022398)the National Natural Science Foundation of China (11271318, 11171296)the Specialized Research Fund for the Doctoral Program of Higher Education of China (20110101110010)
文摘For a field k and two finite groups G and X, when G acts on X from the right by group automorphisms, there is a Hopf algebra structure on k-space (kX°P)* kG (see Theorem 2.1), called a non-balanced quantum double and denoted by Dx(G). In this paper, some Hopf algebra properties of Dx (G) are given, the representation types of Dx (G) viewed as a k-algebra are discussed, the algebra structure and module category over Dx(G) are studied. Since the Hopf algebra structure of non-balanced quantum double DX (G) generMizes the usual quantum double D(G) for a finite group G, all results about Dx(G) in this paper can also be used to describe D(G) as a special case and the universal R-matrix of Dx (G) provides more solutions of Yang-Baxter equation.
基金Project supported by the Shiraz University of Technology, Iran
文摘The differential cross-section for electronic Raman scattering in double semi-parabolic quantum wells of typical GaAs/AlxGa1-xAs is investigated numerically with the effective-mass approximation. The dependence of the differential cross-section on structural parameters such as the barrier width and the well widths is studied. Our results indicate that the electronic Raman scattering is affected by the geometrical size and can be negligible in the symmetric double-well case.