The incoherent control of finite-level quantum systems is investigated. Following a brief introduction to coherent control paradigms in quantum control, a control problem that can not be accomplished using only cohere...The incoherent control of finite-level quantum systems is investigated. Following a brief introduction to coherent control paradigms in quantum control, a control problem that can not be accomplished using only coherent control is presented. For such a control problem, it is proved that it can be accomplished using incoherent control based on projective measurement and coherent control for two classes of finite-level quantum systems, i.e., eigenstate controllable quantum systems and wavefunction controllable quantum systems.展开更多
Using time-dependent multilevel approach （TDML）, this paper studies the dynamics of coherent control of Rydberg lithium atoms and demonstrates that Rydberg lithium atoms can be transferred to states of higher princi...Using time-dependent multilevel approach （TDML）, this paper studies the dynamics of coherent control of Rydberg lithium atoms and demonstrates that Rydberg lithium atoms can be transferred to states of higher principal quantum number by exposing them to specially designed frequency-chirped laser pulses. The population transfer from n=70 to n=75 states of lithium atoms with efficiency more than 90% is achieved by means of the sequential adiabatic rapid passages. The results agree well with the experimental ones and show that the coherent control of the population transfer from the lower n to the higher n states can be accomplished by the optimization of the chirping parameters and the intensity of laser field.展开更多
Analytical propagation formulas are derived for partially coherent controllable dark-hollow beams （CDHBs） through a thin lens based on the generalized Huygens-Fresnel integral. The expressions of the position for ma...Analytical propagation formulas are derived for partially coherent controllable dark-hollow beams （CDHBs） through a thin lens based on the generalized Huygens-Fresnel integral. The expressions of the position for maximum irradiance on-axis and the relative focal shift are evaluated by the analytical propagation formulas. Our numerical results show that both the relative focal shift and the effective beam width of focused partially coherent CDHBs are mainly determined by the initial transverse coherence width 6g and the Fresnel number Nw, which are also affected by the changes of both the dark-size adjusting parameter p and the order N of CDHBs.展开更多
We investigate the coherent control of spin tunneling for a spin–orbit(SO)coupled boson trapped in a driven triple well.In the high-frequency limit,the quasienergies of the system are obtained analytically and the fi...We investigate the coherent control of spin tunneling for a spin–orbit(SO)coupled boson trapped in a driven triple well.In the high-frequency limit,the quasienergies of the system are obtained analytically and the fine energy band structures are shown.By regulating the driving parameters,we reveal that the directed spin-flipping or spin-conserving tunneling of an SOcoupled boson occurs along different pathways and in different directions.The analytical results are demonstrated by numerical simulations and good agreements are found.Further,an interesting scheme of quantum spin tunneling switch with or without spin-flipping is presented.The results may have potential applications in the design of spintronic devices.展开更多
Using the numerical solution of the time-dependent SchrSdinger equation of a one-dimensional model atom in a two-colour laser field, we have investigated the effects of the potential models on coherent control of atom...Using the numerical solution of the time-dependent SchrSdinger equation of a one-dimensional model atom in a two-colour laser field, we have investigated the effects of the potential models on coherent control of atomic multiphoton ionization. It is found that the photoelectron spectra are obviously different for the long-range （Coulomb-like） and short-range （with no excited bound states） potential model atoms, which are produced by two-colour coherent control of atomic multiphoton ionization in a few laser cycles. Our results indicate that two-colour coherent control of atomic multiphoton ionization can be observed in simulations, depending on the choice of the model potentials.展开更多
A femtosecond laser pulse can be tailored to control the two-photon transitions using the ultra-fast pulse-shaping technique. This paper theoretically and experimentally demonstrates that two-photon transitions in mol...A femtosecond laser pulse can be tailored to control the two-photon transitions using the ultra-fast pulse-shaping technique. This paper theoretically and experimentally demonstrates that two-photon transitions in molecular system with broad absorption line can be effectively controlled by square phase-modulation in frequency domain, and the influence of all parameters characterizing the square phase-modulation on two-photon transitions is systemically investigated and discussed. The obtained results have potential application in nonlinear spectroscopy and molecular physics.展开更多
In this paper, we study theoretically and experimentally the coherent control of non-resonant two-photon transition in a molecular system （Perylene dissolved in chloroform solution） by shaping the femtosecond pulses...In this paper, we study theoretically and experimentally the coherent control of non-resonant two-photon transition in a molecular system （Perylene dissolved in chloroform solution） by shaping the femtosecond pulses with simple phase patterns （cosinusoidal and π phase step-function shape）. The control efficiency of the two-photon transition probability is correlated with both the laser field and the molecular absorption bandwidth. Our results demonstrate that, the two-photon transition probability in a molecular system can be reduced but not completely eliminated by manipulating the laser field, and the control efficiency is minimal when the molecular absorption bandwidth is larger than twice the laser spectral bandwidth.展开更多
Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades.An intriguing demonstration of coherent control is a so-called“dark pulse”that cancels 2-photon transition pro...Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades.An intriguing demonstration of coherent control is a so-called“dark pulse”that cancels 2-photon transition probabilities despite exposing the target to the full power spectrum of transform-limited laser pulses.However,for larger functional molecules in condensed phase at room temperature,ensemble measurements do typically not allow exerting full control over competing pathways due to the unavoidable influence of the surrounding(mostly complex)environment.Here,we demonstrate room-temperature coherent control exploiting a nonresonant 2-photon transition into a higher excited state of single conjugated polymer chains embedded in a disordered matrix,including proof-of-principle experiments on bulk films.To manipulate the 2-photon transition probability,we exploit complex pulse sequences,created by a systematically varied cosinusoidal spectral phase applied to the excitation laser spectrum.For single molecules,the phase-dependent response varies from molecule to molecule,which reflects the spectral heterogeneity(position,linewidth)of their 2-photon transitions.These data indicate that coherent control of single molecules requires optimization of parameters for each individual molecule.The experimental data are reproduced by a simple model that allows to directly retrieve the 2-photon absorption spectrum of each single molecule.Our coherent-control approach is a powerful and robust way to obtain spectral characteristics of higher excited states of single molecules and to manipulate the excited-state dynamics in condensed phase at room temperature.It holds the potential to be useful for the characterization of complex organic functional materials.展开更多
A periodic layered medium, with unit cells consisting of a dielectric and an electromagnetically-induced transparency （EIT）-based atomic vapor, is designed for light propagation manipulation. Considering that a dest...A periodic layered medium, with unit cells consisting of a dielectric and an electromagnetically-induced transparency （EIT）-based atomic vapor, is designed for light propagation manipulation. Considering that a destructive quantum interference relevant to a two-photon resonance emerges in EIT-based atoms interacting with both control and probe fields, an EIT-based periodic layered medium exhibits a flexible frequency-sensitive optical response, where a very small variation in the probe frequency can lead to a drastic variation in reflectance and transmittance. The present EIT-based periodic layered structure can result in controllable optical processes that depend sensitively on the external control field. The tunable and sensitive optical response induced by the quantum interference of a multi-level atomic system can be applied in the fabrication of new photonic and quantum optical devices. This material will also open a good perspective for the application of such designs in several new fields, including photonic microcircuits or integrated optical circuits.展开更多
This work conducts robust H^(∞)analysis for a class of quantum systems subject to perturbations in the interaction Hamiltonian.A necessary and sufficient condition for the robustly strict bounded real property of thi...This work conducts robust H^(∞)analysis for a class of quantum systems subject to perturbations in the interaction Hamiltonian.A necessary and sufficient condition for the robustly strict bounded real property of this type of uncertain quantum system is proposed.This paper focuses on the study of coherent robust H^(∞)controller design for quantum systems with uncertainties in the interaction Hamiltonian.The desired controller is connected with the uncertain quantum system through direct and indirect couplings.A necessary and sufficient condition is provided to build a connection between the robust H^(∞)control problem and the scaled H^(∞)control problem.A numerical procedure is provided to obtain coefficients of a coherent controller.An example is presented to illustrate the controller design method.展开更多
This paper theoretically investigates the coherent phase control in electron-argon scattering assisted by a bichro- matic laser field. The laser field is composed of a fundamental component and its second harmonic. Th...This paper theoretically investigates the coherent phase control in electron-argon scattering assisted by a bichro- matic laser field. The laser field is composed of a fundamental component and its second harmonic. The incoming and out going states of electron are described by the Volkov wave functions, and the electron-target interaction is treated as a screening potential. Numerical results for differential cross section of multiphoton processes vs the phase difference between the two components of laser field are discussed for several scattering angles and impact energies.展开更多
In this paper, the dynamics of coherent laser control of potassium atoms is studied by using the time-dependent multilevel approach （TDMA）. The calculation results of population transfer are presented with different...In this paper, the dynamics of coherent laser control of potassium atoms is studied by using the time-dependent multilevel approach （TDMA）. The calculation results of population transfer are presented with different laser fields. The results show that the population can be transferred to target state completely by a specially designed laser field.展开更多
A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ...A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ion yield is observed. More than ten-fold changes of ion yield ratio between different products can be realized. The experimental observations further explain the compositions and formation pathways of peaks in the mass spectra. The controlling mechanisms are also discussed.展开更多
The propagation of a weak probe field in a four-level N-type quantum system in the presence of spontaneously generated coherence(SGC) is theoretically investigated. The optical properties of the system are studied and...The propagation of a weak probe field in a four-level N-type quantum system in the presence of spontaneously generated coherence(SGC) is theoretically investigated. The optical properties of the system are studied and it is shown that the group velocity of light pulse can be controlled by relative phase of applied fields. By changing the relative phase of applied fields, the group velocity of light pulse changes from transparent subluminal to the transparent superluminal light propagation. Thus, the phase-controlled absorption-free superluminal light propagation is obtained without applying an incoherent laser fields to the system. The propagation of a weak probe light pulse is studied by solving the Maxwell's wave equation on numerical grid in space and time. Moreover, we study the third order self- and cross-Kerr susceptibility of probe field and calculate the nonlinear cross-phase shift for different values of intensity of applied fields. In addition, we take into account the effect of Doppler broadening on the light pulse propagation and it is found that a suitable choice of laser propagation directions allows us to preserve our results even in the presence of Doppler effect. It is demonstrated that by increasing the Doppler width of distribution to the room temperature,the dispersion changes from transparent subluminal to transparent superluminal light propagation which is our major motivation for this work.展开更多
Reservoir engineering is the term used in quantum control and information technologies to describe manipulating the environment within which an open quantum system operates. Reservoir engineering is essential in appli...Reservoir engineering is the term used in quantum control and information technologies to describe manipulating the environment within which an open quantum system operates. Reservoir engineering is essential in applications where storing quantum information is required. From the control theory perspective, a quantum system is capable of storing quantum information if it possesses a so-called decoherence free subsystem （DFS）. This paper explores pole placement techniques to facilitate synthesis of decoherence free subsystems via coherent quantum feedback control. We discuss limitations of the conventional ＇open loop＇ approach and propose a constructive feedback design methodology for decoherence free subsystem engineering. It captures a quite general dynamic coherent feedback structure which allows systems with decoherence free modes to be synthesized from components which do not have such modes.展开更多
Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect.In the present study,the effect of shark-skin-insp...Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect.In the present study,the effect of shark-skin-inspired riblets on coherent vortex structures in a turbulent boundary layer（TBL） is investigated.This is done by means of tomographic particle image velocimetry（TPIV） measurements in channel fl ws over an acrylic plate of drag-reducing riblets at a friction Reynolds number of 190.The turbulent fl ws over drag-reducing riblets are verifie by a planar time-resolved particle image velocimetry（TRPIV） system initially,and then the TPIV measurements are performed.Two-dimensional（2D） experimental results with a dragreduction rate of around 4.81% are clearly visible over triangle riblets with a peak-to-peak spacing s＋of 14,indicating from the drag-reducing performance that the buffer layer within the TBL has thickened;the logarithmic law region has shifted upward and the Reynolds shear stress decreased.A comparison of the spatial topological distributions of the spanwise vorticity of coherent vortex structures extracted at different wall-normal heights through the improved quadrant splitting method shows that riblets weaken the amplitudesof the spanwise vorticity when ejection（Q2） and sweep（Q4） events occur at the near wall,having the greatest effect on Q4 events in particular.The so-called quadrupole statistical model for coherent structures in the whole TBL is verified Meanwhile,their spatial conditional-averaged topological shapes and the spatial scales of quadrupole coherent vortex structures as a whole in the overlying turbulent fl w over riblets are changed,suggesting that the riblets dampen the momentum and energy exchange between the regions of near-wall and outer portion of the TBL by depressing the bursting events（Q2 and Q4）,thereby reducing the skin friction drag.展开更多
A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled ...A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled quantum teleportation network involving more users is in demand,which satisfies different combinations of users for practical requirements.Here we propose a highly versatile and controlled teleportation network that can switch among various combinations of different users.We use a single continuous-variable six-partite Greenberger-Horne-Zeilinger(GHZ)state to realize such a task by choosing the different measurement and feedback operations.The controlled teleportation network,which includes one sub-network,two sub-networks and three sub-networks,can be realized for different application of user combinations.Furthermore,the coherent feedback control(CFC)can manipulate and improve the teleportation performance.Our approach is flexible and scalable,and would provide a versatile platform for demonstrations of complex quantum communication and quantum computing protocols.展开更多
We discuss the influences of two different types of mechanisms of quantum coherence on optical bistability in a semiconductor quantum well structure.In the first mechanism,only quantum coherence induced by the resonan...We discuss the influences of two different types of mechanisms of quantum coherence on optical bistability in a semiconductor quantum well structure.In the first mechanism,only quantum coherence induced by the resonant coupling of a strong control laser is considered.In the second mechanism,the decay coherence is taken into account under the condition where the control field is weak.In two different cases,optical bistability can be obtained through choosing appropriate physical parameters.Our studies show quantum coherence makes the optical nonlinear effect of the system become stronger,which takes an important role in the process of generating optical bistability.A semiconductor quantum well with flexibility and easy integration in design could potentially be exploited in real solid-state devices.展开更多
The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an ...The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an open anisotropic Rabi lattice by applying quantum dressed master equation embedded with the mean-field approximation.The expanded antibunching effect of photons due to anisotropic qubit–photon interaction,is strongly suppressed by including inter-site photon tunneling,whereas the giant photon bunching keeps robust with weak inter-site photon tunneling strength.The microscopic processes for photon antibunching and bunching effects are presented based on incoherent transitions between eigenstates.The photon squeezing is also analyzed under the influences of qubit–photon coupling and anisotropic factor.The quadrature squeezing shows persistency by tuning on the inter-site photon tunneling,and becomes dramatically pronounced at the small anisotropic factor.Moreover,the increasing number of qubits significantly enhances quadrature squeezing with strong qubit–photon interaction.We hope such results may provide physical insights into efficient generation and manipulation of nonclassical features of photons in quantum light–matter interacting lattice systems.展开更多
基金supported by the National Natural Science Foundation of China(60805029and60703083)the project from the State KeyLaboratory of Industrial Control Technology,Zhejiang University
文摘The incoherent control of finite-level quantum systems is investigated. Following a brief introduction to coherent control paradigms in quantum control, a control problem that can not be accomplished using only coherent control is presented. For such a control problem, it is proved that it can be accomplished using incoherent control based on projective measurement and coherent control for two classes of finite-level quantum systems, i.e., eigenstate controllable quantum systems and wavefunction controllable quantum systems.
基金Project supported by the National Natural Science Foundation of China(Grant No.10774039)the Basic Research Program of Education Bureau of Henan Province of China(Grant No.072300410130)
文摘Using time-dependent multilevel approach （TDML）, this paper studies the dynamics of coherent control of Rydberg lithium atoms and demonstrates that Rydberg lithium atoms can be transferred to states of higher principal quantum number by exposing them to specially designed frequency-chirped laser pulses. The population transfer from n=70 to n=75 states of lithium atoms with efficiency more than 90% is achieved by means of the sequential adiabatic rapid passages. The results agree well with the experimental ones and show that the coherent control of the population transfer from the lower n to the higher n states can be accomplished by the optimization of the chirping parameters and the intensity of laser field.
基金Supported by the National Natural Science Foundation of China under Grant No 61201193
文摘Analytical propagation formulas are derived for partially coherent controllable dark-hollow beams （CDHBs） through a thin lens based on the generalized Huygens-Fresnel integral. The expressions of the position for maximum irradiance on-axis and the relative focal shift are evaluated by the analytical propagation formulas. Our numerical results show that both the relative focal shift and the effective beam width of focused partially coherent CDHBs are mainly determined by the initial transverse coherence width 6g and the Fresnel number Nw, which are also affected by the changes of both the dark-size adjusting parameter p and the order N of CDHBs.
基金supported by the Scientific Research Foundation of Hunan Provincial Education Department under Grants No.21B0063 and No.18C0027the Hunan Provincial Natural Science Foundation of China under Grants No.2021JJ30435 and No.2017JJ3208the National Natural Science Foundation of China under Grant No.11747034。
文摘We investigate the coherent control of spin tunneling for a spin–orbit(SO)coupled boson trapped in a driven triple well.In the high-frequency limit,the quasienergies of the system are obtained analytically and the fine energy band structures are shown.By regulating the driving parameters,we reveal that the directed spin-flipping or spin-conserving tunneling of an SOcoupled boson occurs along different pathways and in different directions.The analytical results are demonstrated by numerical simulations and good agreements are found.Further,an interesting scheme of quantum spin tunneling switch with or without spin-flipping is presented.The results may have potential applications in the design of spintronic devices.
基金Project supported by the National Natural Science Foundation of China （Grant No 10674112） and the Young Teachers Foundation of Northwest Normal University （Grant No NWNU-QN-04-25）.
文摘Using the numerical solution of the time-dependent SchrSdinger equation of a one-dimensional model atom in a two-colour laser field, we have investigated the effects of the potential models on coherent control of atomic multiphoton ionization. It is found that the photoelectron spectra are obviously different for the long-range （Coulomb-like） and short-range （with no excited bound states） potential model atoms, which are produced by two-colour coherent control of atomic multiphoton ionization in a few laser cycles. Our results indicate that two-colour coherent control of atomic multiphoton ionization can be observed in simulations, depending on the choice of the model potentials.
基金supported by the National Natural Science Foundation of China (Grant No 10574046)National Key Project for Basic Research of China (Grant Nos 2006CB806006 and 2006CB921105)+2 种基金Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT), Program for New Century Excellent Talents in University (NCET-04-0420)the Doctoral Program of High Education (Grant No 20050269011)Phosphor Program sponsored by Shanghai Science and Technology Committee (Grant No 06QH14003)
文摘A femtosecond laser pulse can be tailored to control the two-photon transitions using the ultra-fast pulse-shaping technique. This paper theoretically and experimentally demonstrates that two-photon transitions in molecular system with broad absorption line can be effectively controlled by square phase-modulation in frequency domain, and the influence of all parameters characterizing the square phase-modulation on two-photon transitions is systemically investigated and discussed. The obtained results have potential application in nonlinear spectroscopy and molecular physics.
基金Project supported by Shanghai Leading Academic Discipline Project (Grant No. B408)National Key Program for Basic Research of China (Grant Nos. 2006CB806006 and 2006CB921105)+1 种基金Ministry of Education of China (Grant No. 30800)Shanghai Municipal Science and Technology Commission (Grant Nos. 07DZ22025,09142200501 and 09ZR1409300)
文摘In this paper, we study theoretically and experimentally the coherent control of non-resonant two-photon transition in a molecular system （Perylene dissolved in chloroform solution） by shaping the femtosecond pulses with simple phase patterns （cosinusoidal and π phase step-function shape）. The control efficiency of the two-photon transition probability is correlated with both the laser field and the molecular absorption bandwidth. Our results demonstrate that, the two-photon transition probability in a molecular system can be reduced but not completely eliminated by manipulating the laser field, and the control efficiency is minimal when the molecular absorption bandwidth is larger than twice the laser spectral bandwidth.
基金supported by the China Scholarship Council(no.202006170068).
文摘Coherent control has been achieved in atoms and small molecules in gas phase during the past few decades.An intriguing demonstration of coherent control is a so-called“dark pulse”that cancels 2-photon transition probabilities despite exposing the target to the full power spectrum of transform-limited laser pulses.However,for larger functional molecules in condensed phase at room temperature,ensemble measurements do typically not allow exerting full control over competing pathways due to the unavoidable influence of the surrounding(mostly complex)environment.Here,we demonstrate room-temperature coherent control exploiting a nonresonant 2-photon transition into a higher excited state of single conjugated polymer chains embedded in a disordered matrix,including proof-of-principle experiments on bulk films.To manipulate the 2-photon transition probability,we exploit complex pulse sequences,created by a systematically varied cosinusoidal spectral phase applied to the excitation laser spectrum.For single molecules,the phase-dependent response varies from molecule to molecule,which reflects the spectral heterogeneity(position,linewidth)of their 2-photon transitions.These data indicate that coherent control of single molecules requires optimization of parameters for each individual molecule.The experimental data are reproduced by a simple model that allows to directly retrieve the 2-photon absorption spectrum of each single molecule.Our coherent-control approach is a powerful and robust way to obtain spectral characteristics of higher excited states of single molecules and to manipulate the excited-state dynamics in condensed phase at room temperature.It holds the potential to be useful for the characterization of complex organic functional materials.
基金supported by the Taiwan Science Council (Nos.NSC 99-2811-M-216-001 and NSC 99-2112-M-216-002)the National Natural Science Foundation of China (Nos.60990320 and 60990322)+1 种基金the Natural Science Foundation of Zhejiang Province in China (No.Y6100280)the Fundamental Research Funds for the Central Universities of China
文摘A periodic layered medium, with unit cells consisting of a dielectric and an electromagnetically-induced transparency （EIT）-based atomic vapor, is designed for light propagation manipulation. Considering that a destructive quantum interference relevant to a two-photon resonance emerges in EIT-based atoms interacting with both control and probe fields, an EIT-based periodic layered medium exhibits a flexible frequency-sensitive optical response, where a very small variation in the probe frequency can lead to a drastic variation in reflectance and transmittance. The present EIT-based periodic layered structure can result in controllable optical processes that depend sensitively on the external control field. The tunable and sensitive optical response induced by the quantum interference of a multi-level atomic system can be applied in the fabrication of new photonic and quantum optical devices. This material will also open a good perspective for the application of such designs in several new fields, including photonic microcircuits or integrated optical circuits.
基金supported by the National Natural Science Foundation of China(61803132,61828303,61803389)the U.S.Office of Naval Research Global(N62909-19-1-2129)the Australian Research’s Discovery Projects Funding Scheme under Project DP190101566。
文摘This work conducts robust H^(∞)analysis for a class of quantum systems subject to perturbations in the interaction Hamiltonian.A necessary and sufficient condition for the robustly strict bounded real property of this type of uncertain quantum system is proposed.This paper focuses on the study of coherent robust H^(∞)controller design for quantum systems with uncertainties in the interaction Hamiltonian.The desired controller is connected with the uncertain quantum system through direct and indirect couplings.A necessary and sufficient condition is provided to build a connection between the robust H^(∞)control problem and the scaled H^(∞)control problem.A numerical procedure is provided to obtain coefficients of a coherent controller.An example is presented to illustrate the controller design method.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10874169 and 10674125)the National Basic Research Program of China (Grant No. 2007CB925200)S.-M. Li is grateful to Deutscher Akademischer Austauschdienst and Deutsche Forschungsgemeinschaft for financial support during his stay in Germany
文摘This paper theoretically investigates the coherent phase control in electron-argon scattering assisted by a bichro- matic laser field. The laser field is composed of a fundamental component and its second harmonic. The incoming and out going states of electron are described by the Volkov wave functions, and the electron-target interaction is treated as a screening potential. Numerical results for differential cross section of multiphoton processes vs the phase difference between the two components of laser field are discussed for several scattering angles and impact energies.
基金Project supported by the Natural Science Foundation of Henan province, China （Grant No 0411011900）.
文摘In this paper, the dynamics of coherent laser control of potassium atoms is studied by using the time-dependent multilevel approach （TDMA）. The calculation results of population transfer are presented with different laser fields. The results show that the population can be transferred to target state completely by a specially designed laser field.
基金Project supported by the National Basic Research Program of China (973 Program) (Grant No.2013CB922200)the National Natural Science Foundation of China,(Grant Nos.10774056 and 10974070)+1 种基金the Fundamental Research Funds for the Central Universities,China (Grant No.200903371)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No.20100061110045)
文摘A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ion yield is observed. More than ten-fold changes of ion yield ratio between different products can be realized. The experimental observations further explain the compositions and formation pathways of peaks in the mass spectra. The controlling mechanisms are also discussed.
文摘The propagation of a weak probe field in a four-level N-type quantum system in the presence of spontaneously generated coherence(SGC) is theoretically investigated. The optical properties of the system are studied and it is shown that the group velocity of light pulse can be controlled by relative phase of applied fields. By changing the relative phase of applied fields, the group velocity of light pulse changes from transparent subluminal to the transparent superluminal light propagation. Thus, the phase-controlled absorption-free superluminal light propagation is obtained without applying an incoherent laser fields to the system. The propagation of a weak probe light pulse is studied by solving the Maxwell's wave equation on numerical grid in space and time. Moreover, we study the third order self- and cross-Kerr susceptibility of probe field and calculate the nonlinear cross-phase shift for different values of intensity of applied fields. In addition, we take into account the effect of Doppler broadening on the light pulse propagation and it is found that a suitable choice of laser propagation directions allows us to preserve our results even in the presence of Doppler effect. It is demonstrated that by increasing the Doppler width of distribution to the room temperature,the dispersion changes from transparent subluminal to transparent superluminal light propagation which is our major motivation for this work.
文摘Reservoir engineering is the term used in quantum control and information technologies to describe manipulating the environment within which an open quantum system operates. Reservoir engineering is essential in applications where storing quantum information is required. From the control theory perspective, a quantum system is capable of storing quantum information if it possesses a so-called decoherence free subsystem （DFS）. This paper explores pole placement techniques to facilitate synthesis of decoherence free subsystems via coherent quantum feedback control. We discuss limitations of the conventional ＇open loop＇ approach and propose a constructive feedback design methodology for decoherence free subsystem engineering. It captures a quite general dynamic coherent feedback structure which allows systems with decoherence free modes to be synthesized from components which do not have such modes.
基金supported by the National Natural Science Foundation of China (Grants 11332006,11272233,and 11411130150)the foundation from the China Scholarship Council (CSC) (Grant 201306250092)the Foundation Project for Outstanding Doctoral Dissertations of Tianjin University
文摘Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect.In the present study,the effect of shark-skin-inspired riblets on coherent vortex structures in a turbulent boundary layer（TBL） is investigated.This is done by means of tomographic particle image velocimetry（TPIV） measurements in channel fl ws over an acrylic plate of drag-reducing riblets at a friction Reynolds number of 190.The turbulent fl ws over drag-reducing riblets are verifie by a planar time-resolved particle image velocimetry（TRPIV） system initially,and then the TPIV measurements are performed.Two-dimensional（2D） experimental results with a dragreduction rate of around 4.81% are clearly visible over triangle riblets with a peak-to-peak spacing s＋of 14,indicating from the drag-reducing performance that the buffer layer within the TBL has thickened;the logarithmic law region has shifted upward and the Reynolds shear stress decreased.A comparison of the spatial topological distributions of the spanwise vorticity of coherent vortex structures extracted at different wall-normal heights through the improved quadrant splitting method shows that riblets weaken the amplitudesof the spanwise vorticity when ejection（Q2） and sweep（Q4） events occur at the near wall,having the greatest effect on Q4 events in particular.The so-called quadrupole statistical model for coherent structures in the whole TBL is verified Meanwhile,their spatial conditional-averaged topological shapes and the spatial scales of quadrupole coherent vortex structures as a whole in the overlying turbulent fl w over riblets are changed,suggesting that the riblets dampen the momentum and energy exchange between the regions of near-wall and outer portion of the TBL by depressing the bursting events（Q2 and Q4）,thereby reducing the skin friction drag.
基金Project supported by the Natural Science Foundation of Shanxi Province of China (Grant No. 202203021221214)the National Natural Science Foundation of China (Grant Nos. 62122044, 62135008, 61925503, 11904218, 12004276, 12147215, and 11834010)+4 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province of China (Grant Nos. 2019L0092 and 2020L0029)the Key Project of the National Key Research and Development Program of China (Grant No. 2022YFA1404500)the Program for the Innovative Talents of Higher Education Institutions of Shanxi Province of Chinathe Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxithe Fund for Shanxi “1331 Project” Key Subjects Construction
文摘A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled quantum teleportation network involving more users is in demand,which satisfies different combinations of users for practical requirements.Here we propose a highly versatile and controlled teleportation network that can switch among various combinations of different users.We use a single continuous-variable six-partite Greenberger-Horne-Zeilinger(GHZ)state to realize such a task by choosing the different measurement and feedback operations.The controlled teleportation network,which includes one sub-network,two sub-networks and three sub-networks,can be realized for different application of user combinations.Furthermore,the coherent feedback control(CFC)can manipulate and improve the teleportation performance.Our approach is flexible and scalable,and would provide a versatile platform for demonstrations of complex quantum communication and quantum computing protocols.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11165008 and 11065007)the Natural Science Foundation of Jiangxi Province,China (Grant Nos. 20114BAB202001 and 2010GQW0011)the Science Foundation of East China Jiaotong University,China (Grant No. 10JC03)
文摘We discuss the influences of two different types of mechanisms of quantum coherence on optical bistability in a semiconductor quantum well structure.In the first mechanism,only quantum coherence induced by the resonant coupling of a strong control laser is considered.In the second mechanism,the decay coherence is taken into account under the condition where the control field is weak.In two different cases,optical bistability can be obtained through choosing appropriate physical parameters.Our studies show quantum coherence makes the optical nonlinear effect of the system become stronger,which takes an important role in the process of generating optical bistability.A semiconductor quantum well with flexibility and easy integration in design could potentially be exploited in real solid-state devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.11874011)the Opening Project of Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology.
文摘The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an open anisotropic Rabi lattice by applying quantum dressed master equation embedded with the mean-field approximation.The expanded antibunching effect of photons due to anisotropic qubit–photon interaction,is strongly suppressed by including inter-site photon tunneling,whereas the giant photon bunching keeps robust with weak inter-site photon tunneling strength.The microscopic processes for photon antibunching and bunching effects are presented based on incoherent transitions between eigenstates.The photon squeezing is also analyzed under the influences of qubit–photon coupling and anisotropic factor.The quadrature squeezing shows persistency by tuning on the inter-site photon tunneling,and becomes dramatically pronounced at the small anisotropic factor.Moreover,the increasing number of qubits significantly enhances quadrature squeezing with strong qubit–photon interaction.We hope such results may provide physical insights into efficient generation and manipulation of nonclassical features of photons in quantum light–matter interacting lattice systems.
