Quantum coherence,as a more general quantum resource compared to quantum entanglement,has attracted increasing attention over recent years.Establishing stable quantum coherence is crucial for implementing reliable qua...Quantum coherence,as a more general quantum resource compared to quantum entanglement,has attracted increasing attention over recent years.Establishing stable quantum coherence is crucial for implementing reliable quantum information tasks.In this study,we propose a scheme to generate stable quantum coherence of two qubits via an epsilon-near-zero(ENZ)waveguide.We find that employing Si3N4rather than SiO2results in stronger qubit-qubit coupling and maximal quantum coherence in a certain range.We derive analytical expressions for both quantum coherence and quantum entanglement,allowing for direct comparison within a unified framework.To achieve stable quantum coherence,classical field driving is introduced.We find that stable coherence is much larger and easier mediated than that of stable entanglement.Our work contributes to the creation of a new stable quantum resource via an ENZ waveguide.展开更多
The resource theories of quantum coherence attract a lot of attentioI2 in recent years. Especially, the monotonicity property plays a crucial role here. In this paper we investigate the monotonicity property for the c...The resource theories of quantum coherence attract a lot of attentioI2 in recent years. Especially, the monotonicity property plays a crucial role here. In this paper we investigate the monotonicity property for the coherence measures induced by the Rdnyi a-relative entropy, which present in [Phys. Rev. A 94 （2016） 052336]. We show that the Rdnyi a-relative entropy of coherence does not in general satisfy the monotonicity requirement under the subselection of measurements condition and it also does not satisfy the extension of monotonicity requirement, which presents in [Phys. Rev. A 93 （2016） 032136]. Due to the Rdnyi a-relative entropy of coherence can act as a coherence monotone quantifier, we examine the trade-off relations between coherence and mixedness. Finally, some properties for the single qubit of Rdnyi 2-relative entropy of coherence are derived.展开更多
Quantum coherence is a basic concept in quantum mechanics, representing one of the most fundamental characteristics that distinguishes quantum mechanics from classical physics. Quantum coherence is the basis for multi...Quantum coherence is a basic concept in quantum mechanics, representing one of the most fundamental characteristics that distinguishes quantum mechanics from classical physics. Quantum coherence is the basis for multi-particle interference and quantum entanglement. It is also the essential ingredient for various physical phenomena in quantum optics, quantum information, etc. In recent years, with the proposal of a quantum coherence measurement scheme based on a resource theory framework, quantum coherence as a quantum resource has been extensively investigated. This article reviews the resource theories of quantum coherence and introduces the important applications of quantum coherence in quantum computing,quantum information, and interdisciplinary fields, particularly in quantum thermodynamics and quantum biology. Quantum coherence and its applications are still being explored and developed. We hope this review can provide inspiration for relevant research.展开更多
We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the r...We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the reservoirhaving a Lorentzian spectral density,and analyze how they affect the NAQC defined by the l1 norm and relative entropy.It is shown that the memory effects of this channel on NAQC are state-dependent,and they suppress noticeably the rapiddecay of NAQC for the family of input Bell-like states with one excitation.For the given transmission time of each qubit,we also obtain the regions of the dephasing and memory factors during which there is NAQC in the output states.展开更多
We show that the freezing phenomenon,exhibited by a specific class of two-qubit state under local nondissipative decoherent evolutions,is a common feature of the relative entropy measure of quantum coherence and corre...We show that the freezing phenomenon,exhibited by a specific class of two-qubit state under local nondissipative decoherent evolutions,is a common feature of the relative entropy measure of quantum coherence and correlation.All those measurement outcomes,preserve a constant value in the considered noisy channels,but the condition,property and mechanism of the freezing phenomenon for quantum coherence are different from those of the quantum correlation.展开更多
Y and inverted Y-type four-level schemes for optical quantum coherence systems,which may be intuitivelyconsidered to be very simple,have not been studied intensively till now.In this paper,we present the multiformity ...Y and inverted Y-type four-level schemes for optical quantum coherence systems,which may be intuitivelyconsidered to be very simple,have not been studied intensively till now.In this paper,we present the multiformity ofthese two types of schemes by considering that they can be classified into nine possible level styles as the second-ordersub-schemes using laser fields.Further we point out the complexity of their more than one hundred realistic configurationsas the third-order four-level sub-schemes that may appear in the optical quantum coherence experiments.Throughoutthis paper we review which configurations have been studied in some research aspects and which ones not,accordingto our knowledge,in order to be propitious to next steps of theoretical and experimental investigations,especially forapplications in the fields of quantum optics,quantum information science,laser spectroscopy,and so on.展开更多
We present a theoretical study of quantum coherent effects in a A-three-level system with a strong bichromatic coupling field and a weak probe field. When one component of the strong bichromatic coupling field is reso...We present a theoretical study of quantum coherent effects in a A-three-level system with a strong bichromatic coupling field and a weak probe field. When one component of the strong bichromatic coupling field is resonant with a corresponding transition and the other is detuning with an integer fraction of the Rabi frequency of the resonant field, the absorption spectrum exhibits a series of symmetrical doublets. While two frequencies of the strong bichromatic coupling field are symmetrically detuned from the transition, the position and the relative intensity of the absorption peak are both affected by the coupling field intensity and detuning. An explanation of the spectrum is given in term of the dressed-state formalism.展开更多
Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated. It is found that the optical bistability can appear in the negative refraction freque...Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated. It is found that the optical bistability can appear in the negative refraction frequency band, while both the bistability and multi-stability can occur in the positive refraction frequency bands. Therefore, optical bistability can be realized from conventional material to negative index material due to quantum coherence in our scheme.展开更多
An open quantum battery(QB)model of a single qubit system charging in a coherent auxiliary bath(CAB)consisting of a series of independent coherent ancillae is considered.According to the collision charging protocol we...An open quantum battery(QB)model of a single qubit system charging in a coherent auxiliary bath(CAB)consisting of a series of independent coherent ancillae is considered.According to the collision charging protocol we derive a quantum master equation and obtain the analytical solution of QB in a steady state.We find that the full charging capacity(or the maximal extractable work(MEW))of QB,in the weak QB-ancilla coupling limit,is positively correlated with the coherence magnitude of ancilla.Combining with the numerical simulations we compare with the charging properties of QB at finite coupling strength,such as the MEW,average charging power and the charging efficiency,when considering the bath to be a thermal auxiliary bath(TAB)and a CAB,respectively.We find that when the QB with CAB,in the weak coupling regime,is in fully charging,both its capacity and charging efficiency can go beyond its classical counterpart,and they increase with the increase of coherence magnitude of ancilla.In addition,the MEW of QB in the regime of relative strong coupling and strong coherent magnitude shows the oscillatory behavior with the charging time increasing,and the first peak value can even be larger than the full charging MEW of QB.This also leads to a much larger average charging power than that of QB with TAB in a short-time charging process.These features suggest that with the help of quantum coherence of CAB it becomes feasible to switch the charging schemes between the long-time slow charging protocol with large capacity and high efficiency and the short-time rapid charging protocol with highly charging power only by adjusting the coupling strength of QB-ancilla.This work clearly demonstrates that the quantum coherence of bath can not only serve as the role of“fuel”of QB to be utilized to improve the QB's charging performance but also provide an alternative way to integrate the different charging protocols into a single QB.展开更多
Quantum coherence and non-Markovianity of an atom in a dissipative cavity under weak measurement are investigated in this work. We find that： the quantum coherence obviously depends on the initial atomic state, the s...Quantum coherence and non-Markovianity of an atom in a dissipative cavity under weak measurement are investigated in this work. We find that： the quantum coherence obviously depends on the initial atomic state, the strength of the weak measurement and its reversal, the atom-cavity coupling constant and the non-Markovian effect. It is obvious that the weak measurement effect protects the coherence better. The quantum coherence is preserved more efficiently for larger atom- cavity coupling. The stronger the non-Markovian effect is, the more slowly the coherence reduces. The quantum coherence can be effectively protected by means of controlling these physical parameters.展开更多
The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model. On the basis ...The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model. On the basis of instanton technique in the spin-coherent-state path-integral representation, both the rigorous Wentzel-Kramers-Brillouin exponent and pre-exponential factor for the ground-state tunnel splitting are obtained. We find that the quantum fluctuations around the classical paths can not only induce a new quantum phase previously reported by Chiolero and Loss (Phys. Rev. Lett. 80 (1998) 169), but also have great influence on the intensity of the ground-state tunnel splitting. Those features clearly have no analogue in the ferromagnetic molecular magnets. We suggest that they may be the universal behaviors in all antiferromagnetic molecular magnets. The analytical results are complemented by exact diagonalization calculation.展开更多
We study the quantum coherence and ground-state phase transition of a four-chain Bose–Hubbard model with the long-range interaction. In a special four-chain Bose–Hubbard model,i.e., each chain only has one optical p...We study the quantum coherence and ground-state phase transition of a four-chain Bose–Hubbard model with the long-range interaction. In a special four-chain Bose–Hubbard model,i.e., each chain only has one optical potential, four types of the ground-state phases are discovered. The effects of the disorder, the on-site interaction and the long-range interaction on the quantum coherence are studied. For the system without the long-range interaction, the quantum coherence changes from one periodic oscillation to two periodic oscillations as the onsite interaction increases. By considering the long-range interaction, the quantum coherence goes back to one periodic oscillation again. The on-site interaction itself suppresses the quantum coherence, both the on-site interaction and long-range interaction together enhance the quantum coherence with the weak disorder. If the disorder strength is increased beyond a critical value,they start to suppress the quantum coherence. In a regular four-chain Bose–Hubbard model, i.e.,each chain has many optical potentials, the ground-state phase transitions are obtained by using the cluster Gutzwiller mean-field method. Exotic ground-state phases are found, i.e., superfluid phase, integer Mott insulator phase, supersolid phase and loophole insulator phase. The combination of the loophole insulator phase and the supersolid phase expands the lobes with the half-integer filling per site for the small ratio β = t_(‖)/t_(⊥).展开更多
We investigate the nonlocal advantage of quantum coherence(NAQC)and entanglement for two spins coupled via the Heisenberg interaction and under the intrinsic decoherence.Solutions of this decoherence model for the ini...We investigate the nonlocal advantage of quantum coherence(NAQC)and entanglement for two spins coupled via the Heisenberg interaction and under the intrinsic decoherence.Solutions of this decoherence model for the initial spin-1/2 and spin-1 maximally entangled states are obtained,based on which we calculate the NAQC and entanglement.In the weak region of magnetic field,the NAQC behaves as a damped oscillation with the time evolves,while the entanglement decays exponentially(behaves as a damped oscillation)for the spin-1/2(spin-1)case.Moreover,the decay of both the NAQC and entanglement can be suppressed significantly by tuning the magnetic field and anisotropy of the spin interaction to some decoherence-rate-determined optimal values.展开更多
Energy is often partitioned into heat and work by two independent paths corresponding to the change in the eigenenergies or the probability distributions of a quantum system. The discrepancies of the heat and work for...Energy is often partitioned into heat and work by two independent paths corresponding to the change in the eigenenergies or the probability distributions of a quantum system. The discrepancies of the heat and work for various quantum thermodynamic processes have not been well characterized in literature. Here we show how the work in quantum machines is differentially related to the isochoric, isothermal, and adiabatic processes. We prove that the energy exchanges during the quantum isochoric and isothermal processes are simply depending on the change in the eigenenergies or the probability distributions. However, for a time-dependent system in a non-adiabatic quantum evolution, the transitions between the different quantum states representing the quantum coherence can affect the essential thermodynamic properties, and thus the general definitions of the heat and work should be clarified with respect to the microscopic generic time-dependent system. By integrating the coherence effects in the exactly-solvable dynamics of quantum-spin precession, the internal energy is rigorously transferred as the work in the thermodynamic adiabatic process. The present study demonstrates that the quantum adiabatic process is sufficient but not necessary for the thermodynamic adiabatic process.展开更多
Instanton configurations of （1＋1）-dimensions in an antiferromagnetic biaxial-anisotropy-spin-chain are obtained explicitly in the strong anisotropy limit, which interpolate between degenerate equilibrium orientatio...Instanton configurations of （1＋1）-dimensions in an antiferromagnetic biaxial-anisotropy-spin-chain are obtained explicitly in the strong anisotropy limit, which interpolate between degenerate equilibrium orientations of the Neel vector along easy axis and are seen to be responsible for quantum tunneling. Macroscopic quantum coherence of the domain walls is demonstrated in terms of the instantons.展开更多
Taking into account the dephasing process in the realistic atomic ensemble,we theoretically study the generation of atomic spin squeezing via atomic coherence induced by the coupling and probe fields.Using the Heisenb...Taking into account the dephasing process in the realistic atomic ensemble,we theoretically study the generation of atomic spin squeezing via atomic coherence induced by the coupling and probe fields.Using the Heisenberg–Langevin approach,we find that the perfect spin squeezing in the X component can be obtained while the coupling and probe fields produce the maximum coherence between the ground state sublevels 1 and 2.Moreover,the degree of atomic spin squeezing in the X component can be strengthened with the increasing atomic density and/or Rabi frequency of the mixing field.The theoretical results provide a proof-of-principle demonstration of generating the atomic spin squeezing via quantum coherence in the realistic atomic ensemble which may find potential applications in quantum information processing and quantum networks.展开更多
The exact dynamics of an open quantum system consisting of one qubit driven by a classical driving field is investigated. Our attention is focused on the influences of single-and two-photon excitations on the dynamics...The exact dynamics of an open quantum system consisting of one qubit driven by a classical driving field is investigated. Our attention is focused on the influences of single-and two-photon excitations on the dynamics of quantum coherence and quantum entanglement. It is shown that the atomic coherence can be improved or even maintained by the classical driving field, the non-Markovian effect, and the atom-reservoir detuning. The interconversion between the atomic coherence and the atom-reservoir entanglement exists and can be controlled by the appropriate conditions. The conservation of coherence for different partitions is explored, and the dynamics of a system with two-photon excitations is different from the case of single-photon excitation.展开更多
We analytically investigate Multiple Quantum(MQ) NMR dynamics in a mixed-three-spin(1/2,1,1/2)system with XXX Heisenberg model at the front of an external homogeneous magnetic field B. A single-ion anisotropy property...We analytically investigate Multiple Quantum(MQ) NMR dynamics in a mixed-three-spin(1/2,1,1/2)system with XXX Heisenberg model at the front of an external homogeneous magnetic field B. A single-ion anisotropy property ζ is considered for the spin-1. The intensities dependence of MQ NMR coherences on their orders(zeroth and second orders) for two pairs of spins(1,1/2) and(1/2,1/2) of the favorite tripartite system are obtained. It is also investigated dynamics of the pairwise quantum entanglement for the bipartite(sub)systems(1,1/2) and(1/2,1/2)permanently coupled by, respectively, coupling constants J_1 and J_2, by means of concurrence and fidelity. Then, some straightforward comparisons are done between these quantities and the intensities of MQ NMR coherences and ultimately some interesting results are reported. We also show that the time evolution of MQ coherences based on the reduced density matrix of the pair spins(1,1/2) is closely connected with the dynamics of the pairwise entanglement. Finally, we prove that one can introduce MQ coherence of the zeroth order corresponds to the pair spins(1,1/2) as an entanglement witness at some special time intervals.展开更多
Coherence is a key resource in quantum information science.Exactly understanding and controlling the variation of coherence are vital for implementation in realistic quantum systems.Using P-representation of density m...Coherence is a key resource in quantum information science.Exactly understanding and controlling the variation of coherence are vital for implementation in realistic quantum systems.Using P-representation of density matrix,we obtain the analytical solution of the master equation for the classical states in the non-Markovian process and investigate the coherent dynamics of Gaussian states.It is found that quantum coherence can be preserved in such a process if the coupling strength between system and environment exceeds a threshold value.We also discuss the characteristic function of the Gaussian states in the non-Markovian process,which provides an inevitable bridge for the control and operation of quantum coherence.展开更多
A general definition of quantum coherence is developed from analysis of superposition, entanglement, chemical bonding behavior, and basic phenomena of classical mechanics. Various properties of atoms can be better exp...A general definition of quantum coherence is developed from analysis of superposition, entanglement, chemical bonding behavior, and basic phenomena of classical mechanics. Various properties of atoms can be better explained if these particles are matter waves that embody a spectrum ranging from relatively coherent to decoherent states. It is demonstrated that quantum coherence so defined can comprehensively explain signal transmission in neurons and dynamics of the brain’s emergent electric field, including potential support for the claim that conscious volition is to some degree real rather than an illusion. Recent research in a physiological context suggests that electromagnetic radiation interacts with molecular structure to comprise integrated energy fields. A mechanism is proposed by which quantum coherence as accelerating electric currents in neurons may result in a broadened spectrum of electromagnetic radiation capable of interacting with molecular complexes in the brain and perhaps elsewhere in an organism to influence vibrational and structural properties. Research should investigate whether a consequent energy field is the basic perceptual substrate, with at least some additive electromagnetic wavelengths of this field involved in generating image percepts insofar as they arise from the body, and electromagnetic vibrations the signature of a more diverse phenomenon by which somewhat nondimensional features of perception such as sound, touch, taste, smell, interoceptive sensations, etc. partially arise. If examination of the brain reveals this organ to be composed of a coherence field, structured at least in part by broadened spectrums of EM radiation interacting with molecular components, this has major implications for furthering our model of the matter/mind interface and possibly physical reality in total.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0122300)the Natural Science Foundation of Jiangsu Province(Grant No.BK20231493)the Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province(Grant No.GD202405)。
文摘Quantum coherence,as a more general quantum resource compared to quantum entanglement,has attracted increasing attention over recent years.Establishing stable quantum coherence is crucial for implementing reliable quantum information tasks.In this study,we propose a scheme to generate stable quantum coherence of two qubits via an epsilon-near-zero(ENZ)waveguide.We find that employing Si3N4rather than SiO2results in stronger qubit-qubit coupling and maximal quantum coherence in a certain range.We derive analytical expressions for both quantum coherence and quantum entanglement,allowing for direct comparison within a unified framework.To achieve stable quantum coherence,classical field driving is introduced.We find that stable coherence is much larger and easier mediated than that of stable entanglement.Our work contributes to the creation of a new stable quantum resource via an ENZ waveguide.
基金Supported by National Natural Science Foundation of China under Grant Nos.11271237,11671244,61671280the Higher School Doctoral Subject Foundation of Ministry of Education of China under Grant No.20130202110001+1 种基金Fundamental Research Funds for the Central Universities(GK201502004 and 2016CBY003)the Academic Leaders and Academic Backbones,Shaanxi Normal University under Grant No.16QNGG013
文摘The resource theories of quantum coherence attract a lot of attentioI2 in recent years. Especially, the monotonicity property plays a crucial role here. In this paper we investigate the monotonicity property for the coherence measures induced by the Rdnyi a-relative entropy, which present in [Phys. Rev. A 94 （2016） 052336]. We show that the Rdnyi a-relative entropy of coherence does not in general satisfy the monotonicity requirement under the subselection of measurements condition and it also does not satisfy the extension of monotonicity requirement, which presents in [Phys. Rev. A 93 （2016） 032136]. Due to the Rdnyi a-relative entropy of coherence can act as a coherence monotone quantifier, we examine the trade-off relations between coherence and mixedness. Finally, some properties for the single qubit of Rdnyi 2-relative entropy of coherence are derived.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12175179)the Peng Huaiwu Center for Fundamental Theory (Grant No. 12247103)the Natural Science Basic Research Program of Shaanxi Province (Grant Nos. 2021JCW-19 and 2019JQ-863)。
文摘Quantum coherence is a basic concept in quantum mechanics, representing one of the most fundamental characteristics that distinguishes quantum mechanics from classical physics. Quantum coherence is the basis for multi-particle interference and quantum entanglement. It is also the essential ingredient for various physical phenomena in quantum optics, quantum information, etc. In recent years, with the proposal of a quantum coherence measurement scheme based on a resource theory framework, quantum coherence as a quantum resource has been extensively investigated. This article reviews the resource theories of quantum coherence and introduces the important applications of quantum coherence in quantum computing,quantum information, and interdisciplinary fields, particularly in quantum thermodynamics and quantum biology. Quantum coherence and its applications are still being explored and developed. We hope this review can provide inspiration for relevant research.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11675129,11774406,and 11934018)the National Key R&D Program of China(Grant Nos.2016YFA0302104 and 2016YFA0300600)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Research Program of Beijing Academy of Quantum Information Sciences(Grant No.Y18G07).
文摘We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the reservoirhaving a Lorentzian spectral density,and analyze how they affect the NAQC defined by the l1 norm and relative entropy.It is shown that the memory effects of this channel on NAQC are state-dependent,and they suppress noticeably the rapiddecay of NAQC for the family of input Bell-like states with one excitation.For the given transmission time of each qubit,we also obtain the regions of the dephasing and memory factors during which there is NAQC in the output states.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61675115 and 11304179)
文摘We show that the freezing phenomenon,exhibited by a specific class of two-qubit state under local nondissipative decoherent evolutions,is a common feature of the relative entropy measure of quantum coherence and correlation.All those measurement outcomes,preserve a constant value in the considered noisy channels,but the condition,property and mechanism of the freezing phenomenon for quantum coherence are different from those of the quantum correlation.
基金Supported by the Research Starting Funds of Tianjin Polytechnic University under Grant Nos.20080033 and 20070010
文摘Y and inverted Y-type four-level schemes for optical quantum coherence systems,which may be intuitivelyconsidered to be very simple,have not been studied intensively till now.In this paper,we present the multiformity ofthese two types of schemes by considering that they can be classified into nine possible level styles as the second-ordersub-schemes using laser fields.Further we point out the complexity of their more than one hundred realistic configurationsas the third-order four-level sub-schemes that may appear in the optical quantum coherence experiments.Throughoutthis paper we review which configurations have been studied in some research aspects and which ones not,accordingto our knowledge,in order to be propitious to next steps of theoretical and experimental investigations,especially forapplications in the fields of quantum optics,quantum information science,laser spectroscopy,and so on.
基金Project supported by the Natural Science Foundation of Hebei Province,China(Grant No.A2009000140)
文摘We present a theoretical study of quantum coherent effects in a A-three-level system with a strong bichromatic coupling field and a weak probe field. When one component of the strong bichromatic coupling field is resonant with a corresponding transition and the other is detuning with an integer fraction of the Rabi frequency of the resonant field, the absorption spectrum exhibits a series of symmetrical doublets. While two frequencies of the strong bichromatic coupling field are symmetrically detuned from the transition, the position and the relative intensity of the absorption peak are both affected by the coupling field intensity and detuning. An explanation of the spectrum is given in term of the dressed-state formalism.
基金Project supported by the Fundamental Research Funds for the Central University (Grant Nos.GK201002024 and GK201003003)the National Natural Science Foundation of China (Grant Nos.11104176 and 11104185)+2 种基金the Natural Science Foundation of Shaanxi Province,China (Grant No.2011JQ1008)the Special Fund of Shanghai Outstanding Young Teachers,China (Grant Nos.slg10054 and slg10023)the Innovation Program of Shanghai Municipal Education Commission,China (Grant No.11YZ118)
文摘Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated. It is found that the optical bistability can appear in the negative refraction frequency band, while both the bistability and multi-stability can occur in the positive refraction frequency bands. Therefore, optical bistability can be realized from conventional material to negative index material due to quantum coherence in our scheme.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11775019 and 62173213)the Natural Science Foundation of Shandong Province,China (Grant No.ZR2011FL009)the Shandong Provincial Science and Technology Support Program of Youth Innovation Team in Colleges (Grant Nos.2019KJN041 and 2020KJN005)。
文摘An open quantum battery(QB)model of a single qubit system charging in a coherent auxiliary bath(CAB)consisting of a series of independent coherent ancillae is considered.According to the collision charging protocol we derive a quantum master equation and obtain the analytical solution of QB in a steady state.We find that the full charging capacity(or the maximal extractable work(MEW))of QB,in the weak QB-ancilla coupling limit,is positively correlated with the coherence magnitude of ancilla.Combining with the numerical simulations we compare with the charging properties of QB at finite coupling strength,such as the MEW,average charging power and the charging efficiency,when considering the bath to be a thermal auxiliary bath(TAB)and a CAB,respectively.We find that when the QB with CAB,in the weak coupling regime,is in fully charging,both its capacity and charging efficiency can go beyond its classical counterpart,and they increase with the increase of coherence magnitude of ancilla.In addition,the MEW of QB in the regime of relative strong coupling and strong coherent magnitude shows the oscillatory behavior with the charging time increasing,and the first peak value can even be larger than the full charging MEW of QB.This also leads to a much larger average charging power than that of QB with TAB in a short-time charging process.These features suggest that with the help of quantum coherence of CAB it becomes feasible to switch the charging schemes between the long-time slow charging protocol with large capacity and high efficiency and the short-time rapid charging protocol with highly charging power only by adjusting the coupling strength of QB-ancilla.This work clearly demonstrates that the quantum coherence of bath can not only serve as the role of“fuel”of QB to be utilized to improve the QB's charging performance but also provide an alternative way to integrate the different charging protocols into a single QB.
基金Project supported by the Scientific Research Project of Hunan Provincial Education Department,China(Grant No.16C0949)the Hunan Provincial Innovation Foundation for Postgraduate,China(Grant No.CX2017B177)+1 种基金the National Natural Science Foundation of China(Grant No.11374096)the Doctoral Science Foundation of Hunan Normal University,China
文摘Quantum coherence and non-Markovianity of an atom in a dissipative cavity under weak measurement are investigated in this work. We find that： the quantum coherence obviously depends on the initial atomic state, the strength of the weak measurement and its reversal, the atom-cavity coupling constant and the non-Markovian effect. It is obvious that the weak measurement effect protects the coherence better. The quantum coherence is preserved more efficiently for larger atom- cavity coupling. The stronger the non-Markovian effect is, the more slowly the coherence reduces. The quantum coherence can be effectively protected by means of controlling these physical parameters.
文摘The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model. On the basis of instanton technique in the spin-coherent-state path-integral representation, both the rigorous Wentzel-Kramers-Brillouin exponent and pre-exponential factor for the ground-state tunnel splitting are obtained. We find that the quantum fluctuations around the classical paths can not only induce a new quantum phase previously reported by Chiolero and Loss (Phys. Rev. Lett. 80 (1998) 169), but also have great influence on the intensity of the ground-state tunnel splitting. Those features clearly have no analogue in the ferromagnetic molecular magnets. We suggest that they may be the universal behaviors in all antiferromagnetic molecular magnets. The analytical results are complemented by exact diagonalization calculation.
基金the NSF of China under Grant No.11904242the NSF of Hebei province under Grant No.A2019210280。
文摘We study the quantum coherence and ground-state phase transition of a four-chain Bose–Hubbard model with the long-range interaction. In a special four-chain Bose–Hubbard model,i.e., each chain only has one optical potential, four types of the ground-state phases are discovered. The effects of the disorder, the on-site interaction and the long-range interaction on the quantum coherence are studied. For the system without the long-range interaction, the quantum coherence changes from one periodic oscillation to two periodic oscillations as the onsite interaction increases. By considering the long-range interaction, the quantum coherence goes back to one periodic oscillation again. The on-site interaction itself suppresses the quantum coherence, both the on-site interaction and long-range interaction together enhance the quantum coherence with the weak disorder. If the disorder strength is increased beyond a critical value,they start to suppress the quantum coherence. In a regular four-chain Bose–Hubbard model, i.e.,each chain has many optical potentials, the ground-state phase transitions are obtained by using the cluster Gutzwiller mean-field method. Exotic ground-state phases are found, i.e., superfluid phase, integer Mott insulator phase, supersolid phase and loophole insulator phase. The combination of the loophole insulator phase and the supersolid phase expands the lobes with the half-integer filling per site for the small ratio β = t_(‖)/t_(⊥).
基金the National Natural Science Foundation of China(Grant Nos.11774406 and 11934018)the National Key Research and Develepment Program of China(Grant Nos.2016YFA0302104 and 2016YFA0300600)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Research Program of Beijing Academy of Quantum Information Sciences(Grant No.Y18G07)。
文摘We investigate the nonlocal advantage of quantum coherence(NAQC)and entanglement for two spins coupled via the Heisenberg interaction and under the intrinsic decoherence.Solutions of this decoherence model for the initial spin-1/2 and spin-1 maximally entangled states are obtained,based on which we calculate the NAQC and entanglement.In the weak region of magnetic field,the NAQC behaves as a damped oscillation with the time evolves,while the entanglement decays exponentially(behaves as a damped oscillation)for the spin-1/2(spin-1)case.Moreover,the decay of both the NAQC and entanglement can be suppressed significantly by tuning the magnetic field and anisotropy of the spin interaction to some decoherence-rate-determined optimal values.
基金supported by the National Natural Science Foundation of China(Grant Nos.11421063,11534002,and 51776178)the National Key Basic Research Program of China(Grant Nos.2012CB922104 and 2014CB921403)
文摘Energy is often partitioned into heat and work by two independent paths corresponding to the change in the eigenenergies or the probability distributions of a quantum system. The discrepancies of the heat and work for various quantum thermodynamic processes have not been well characterized in literature. Here we show how the work in quantum machines is differentially related to the isochoric, isothermal, and adiabatic processes. We prove that the energy exchanges during the quantum isochoric and isothermal processes are simply depending on the change in the eigenenergies or the probability distributions. However, for a time-dependent system in a non-adiabatic quantum evolution, the transitions between the different quantum states representing the quantum coherence can affect the essential thermodynamic properties, and thus the general definitions of the heat and work should be clarified with respect to the microscopic generic time-dependent system. By integrating the coherence effects in the exactly-solvable dynamics of quantum-spin precession, the internal energy is rigorously transferred as the work in the thermodynamic adiabatic process. The present study demonstrates that the quantum adiabatic process is sufficient but not necessary for the thermodynamic adiabatic process.
基金Supported by the Natural Science Basic Research Plan in Henan Province of China under Grant No.2007140009
文摘Instanton configurations of （1＋1）-dimensions in an antiferromagnetic biaxial-anisotropy-spin-chain are obtained explicitly in the strong anisotropy limit, which interpolate between degenerate equilibrium orientations of the Neel vector along easy axis and are seen to be responsible for quantum tunneling. Macroscopic quantum coherence of the domain walls is demonstrated in terms of the instantons.
文摘Taking into account the dephasing process in the realistic atomic ensemble,we theoretically study the generation of atomic spin squeezing via atomic coherence induced by the coupling and probe fields.Using the Heisenberg–Langevin approach,we find that the perfect spin squeezing in the X component can be obtained while the coupling and probe fields produce the maximum coherence between the ground state sublevels 1 and 2.Moreover,the degree of atomic spin squeezing in the X component can be strengthened with the increasing atomic density and/or Rabi frequency of the mixing field.The theoretical results provide a proof-of-principle demonstration of generating the atomic spin squeezing via quantum coherence in the realistic atomic ensemble which may find potential applications in quantum information processing and quantum networks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61675115,11204156,11574178,11304179,and 11647172)the Science and Technology Plan Projects of Shandong University,China(Grant No.J16LJ52)
文摘The exact dynamics of an open quantum system consisting of one qubit driven by a classical driving field is investigated. Our attention is focused on the influences of single-and two-photon excitations on the dynamics of quantum coherence and quantum entanglement. It is shown that the atomic coherence can be improved or even maintained by the classical driving field, the non-Markovian effect, and the atom-reservoir detuning. The interconversion between the atomic coherence and the atom-reservoir entanglement exists and can be controlled by the appropriate conditions. The conservation of coherence for different partitions is explored, and the dynamics of a system with two-photon excitations is different from the case of single-photon excitation.
文摘We analytically investigate Multiple Quantum(MQ) NMR dynamics in a mixed-three-spin(1/2,1,1/2)system with XXX Heisenberg model at the front of an external homogeneous magnetic field B. A single-ion anisotropy property ζ is considered for the spin-1. The intensities dependence of MQ NMR coherences on their orders(zeroth and second orders) for two pairs of spins(1,1/2) and(1/2,1/2) of the favorite tripartite system are obtained. It is also investigated dynamics of the pairwise quantum entanglement for the bipartite(sub)systems(1,1/2) and(1/2,1/2)permanently coupled by, respectively, coupling constants J_1 and J_2, by means of concurrence and fidelity. Then, some straightforward comparisons are done between these quantities and the intensities of MQ NMR coherences and ultimately some interesting results are reported. We also show that the time evolution of MQ coherences based on the reduced density matrix of the pair spins(1,1/2) is closely connected with the dynamics of the pairwise entanglement. Finally, we prove that one can introduce MQ coherence of the zeroth order corresponds to the pair spins(1,1/2) as an entanglement witness at some special time intervals.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11405100,11404377 and 11674360the Natural Science Basic Research Plan of Shaanxi Province of China under Grant No 2015JM1032the Doctoral Research Fund of Shaanxi University of Science and Technology of China under Grant No 2018BJ-02
文摘Coherence is a key resource in quantum information science.Exactly understanding and controlling the variation of coherence are vital for implementation in realistic quantum systems.Using P-representation of density matrix,we obtain the analytical solution of the master equation for the classical states in the non-Markovian process and investigate the coherent dynamics of Gaussian states.It is found that quantum coherence can be preserved in such a process if the coupling strength between system and environment exceeds a threshold value.We also discuss the characteristic function of the Gaussian states in the non-Markovian process,which provides an inevitable bridge for the control and operation of quantum coherence.
文摘A general definition of quantum coherence is developed from analysis of superposition, entanglement, chemical bonding behavior, and basic phenomena of classical mechanics. Various properties of atoms can be better explained if these particles are matter waves that embody a spectrum ranging from relatively coherent to decoherent states. It is demonstrated that quantum coherence so defined can comprehensively explain signal transmission in neurons and dynamics of the brain’s emergent electric field, including potential support for the claim that conscious volition is to some degree real rather than an illusion. Recent research in a physiological context suggests that electromagnetic radiation interacts with molecular structure to comprise integrated energy fields. A mechanism is proposed by which quantum coherence as accelerating electric currents in neurons may result in a broadened spectrum of electromagnetic radiation capable of interacting with molecular complexes in the brain and perhaps elsewhere in an organism to influence vibrational and structural properties. Research should investigate whether a consequent energy field is the basic perceptual substrate, with at least some additive electromagnetic wavelengths of this field involved in generating image percepts insofar as they arise from the body, and electromagnetic vibrations the signature of a more diverse phenomenon by which somewhat nondimensional features of perception such as sound, touch, taste, smell, interoceptive sensations, etc. partially arise. If examination of the brain reveals this organ to be composed of a coherence field, structured at least in part by broadened spectrums of EM radiation interacting with molecular components, this has major implications for furthering our model of the matter/mind interface and possibly physical reality in total.
