In this paper, we investigate the entropy squeezing for a two-level atom interacting with two quantized fields through Raman coupling. We obtain the dynamical evolution of the total system under the influence of intri...In this paper, we investigate the entropy squeezing for a two-level atom interacting with two quantized fields through Raman coupling. We obtain the dynamical evolution of the total system under the influence of intrinsic decoherence when the two quantized fields are prepared in a two-mode squeezing vacuum state initially. The effects of the field squeezing factor, the two-level atomic transition frequency, the second field frequency and the intrinsic decoherence on the entropy squeezing are discussed. Without intrinsic decoherence, the increase of field squeezing factor can break the entropy squeezing. The two-level atomic transition frequency changes only the period of oscillation but not the strength of entropy squeezing. The influence of the second field frequency is complicated. With the intrinsic decoherence taken into consideration, the results show that the stronger the intrinsic decoherence is, the more quickly the entropy squeezing will disappear. The increase of the atomic transition frequency can hasten the disappearance of entropy squeezing.展开更多
Considering intrinsic decoherence, the two-atom two-mode Raman coupled model is investigated in this paper. Utilizing the constants of motion in this model, we obtain the analytic expressions of the density operator o...Considering intrinsic decoherence, the two-atom two-mode Raman coupled model is investigated in this paper. Utilizing the constants of motion in this model, we obtain the analytic expressions of the density operator of the system for investigating the entanglement of two atoms. The speed of entanglement decay increases with the increasing of the coupling coefficient of one atom. The difference between the oscillation periods when the initial state parameter of atomic subsystem belongs to two intervals becomes smaller with the increasing of the coupling coefficient of one atom. The increasing of the initial photon number of the second field can hasten the vanishing of entanglement of atomic subsystem. The robustness of atomic entanglement against decoherence depends on the interval of the initial state parameter of atomic subsystem.展开更多
The Raman-coupled interaction between an atom and a single mode of a cavity field is studied. For the cases in which a light field is initially in a coherent state and in a thermal state separately, we have derived th...The Raman-coupled interaction between an atom and a single mode of a cavity field is studied. For the cases in which a light field is initially in a coherent state and in a thermal state separately, we have derived the analytic expressions for the time evolutions of atomic population difference W, modulus B of the Bloch vector, and entropy E. We find that the time evolutions of these quantities are periodic with a period of π. The maxima of W and B appear at the scaled interaction time points τ- = kπ（k = 0, 1, 2,...）. At these time points, E = 0, which shows that the atom and the field are not entangled. Between these time points, E ≠ 0, which means that the atom and the field are entangled. When the field is initially in a coherent state, near the maxima, the envelope of W is a Gaussian function with a variance of 1/（4n^-）（n^- is the mean number of photons）. Under the envelope, W oscillates at a frequency of n^-/π. When the field is initially in a thermal state, near the maxima, W is a Lorentz function with a width of 1/n^-.展开更多
We propose a scheme for controllably implementing an N-qubit phase gate by one step within a ground-state subspace of N three-state atoms trapped in a cavity through a double Raman passage. We can extend our scheme to...We propose a scheme for controllably implementing an N-qubit phase gate by one step within a ground-state subspace of N three-state atoms trapped in a cavity through a double Raman passage. We can extend our scheme to the realisation of an arbitrary N-qubit phase gate by appropriately adjusting coupling strengths and detunings between atoms and external driving fields. The advantage of this one-step scheme is its robustness against decoherence.展开更多
Two-dimensional transition metal dichalcogenides（TMDs） have attracted extensive attention due to their many novel properties.The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds,...Two-dimensional transition metal dichalcogenides（TMDs） have attracted extensive attention due to their many novel properties.The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds,while van der Waals interactions combine the layers together.This makes its lattice dynamics layer-number dependent.The evolutions of ultralow frequency（〈 50 cm^（-1）） modes,such as shear and layer-breathing modes have been well-established.Here,we review the layer-number dependent high-frequency（〉 50 cm^（-1）） vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes,known as Davydov splitting.Such Davydov splitting can be well described by a van der Waals model,which directly links the splitting with the interlayer coupling.Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 10374007)
文摘In this paper, we investigate the entropy squeezing for a two-level atom interacting with two quantized fields through Raman coupling. We obtain the dynamical evolution of the total system under the influence of intrinsic decoherence when the two quantized fields are prepared in a two-mode squeezing vacuum state initially. The effects of the field squeezing factor, the two-level atomic transition frequency, the second field frequency and the intrinsic decoherence on the entropy squeezing are discussed. Without intrinsic decoherence, the increase of field squeezing factor can break the entropy squeezing. The two-level atomic transition frequency changes only the period of oscillation but not the strength of entropy squeezing. The influence of the second field frequency is complicated. With the intrinsic decoherence taken into consideration, the results show that the stronger the intrinsic decoherence is, the more quickly the entropy squeezing will disappear. The increase of the atomic transition frequency can hasten the disappearance of entropy squeezing.
基金Project supported by the National Natural Science Foundation of China (Grant No 10374007)
文摘Considering intrinsic decoherence, the two-atom two-mode Raman coupled model is investigated in this paper. Utilizing the constants of motion in this model, we obtain the analytic expressions of the density operator of the system for investigating the entanglement of two atoms. The speed of entanglement decay increases with the increasing of the coupling coefficient of one atom. The difference between the oscillation periods when the initial state parameter of atomic subsystem belongs to two intervals becomes smaller with the increasing of the coupling coefficient of one atom. The increasing of the initial photon number of the second field can hasten the vanishing of entanglement of atomic subsystem. The robustness of atomic entanglement against decoherence depends on the interval of the initial state parameter of atomic subsystem.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60578055 and 10404007)
文摘The Raman-coupled interaction between an atom and a single mode of a cavity field is studied. For the cases in which a light field is initially in a coherent state and in a thermal state separately, we have derived the analytic expressions for the time evolutions of atomic population difference W, modulus B of the Bloch vector, and entropy E. We find that the time evolutions of these quantities are periodic with a period of π. The maxima of W and B appear at the scaled interaction time points τ- = kπ（k = 0, 1, 2,...）. At these time points, E = 0, which shows that the atom and the field are not entangled. Between these time points, E ≠ 0, which means that the atom and the field are entangled. When the field is initially in a coherent state, near the maxima, the envelope of W is a Gaussian function with a variance of 1/（4n^-）（n^- is the mean number of photons）. Under the envelope, W oscillates at a frequency of n^-/π. When the field is initially in a thermal state, near the maxima, W is a Lorentz function with a width of 1/n^-.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60578055 and 60978009)the National Basic Research Program of China(Grant Nos. 2007CB925204 and 2009CB929604)
文摘We propose a scheme for controllably implementing an N-qubit phase gate by one step within a ground-state subspace of N three-state atoms trapped in a cavity through a double Raman passage. We can extend our scheme to the realisation of an arbitrary N-qubit phase gate by appropriately adjusting coupling strengths and detunings between atoms and external driving fields. The advantage of this one-step scheme is its robustness against decoherence.
基金Project supported by the National Basic Research Program of China(No.2016YFA0301200)the National Natural Science Foundation of China(Nos.11225421,11474277,11434010,61474067,11604326,11574305 and 51527901)the National Young 1000 Talent Plan of China
文摘Two-dimensional transition metal dichalcogenides（TMDs） have attracted extensive attention due to their many novel properties.The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds,while van der Waals interactions combine the layers together.This makes its lattice dynamics layer-number dependent.The evolutions of ultralow frequency（〈 50 cm^（-1）） modes,such as shear and layer-breathing modes have been well-established.Here,we review the layer-number dependent high-frequency（〉 50 cm^（-1）） vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes,known as Davydov splitting.Such Davydov splitting can be well described by a van der Waals model,which directly links the splitting with the interlayer coupling.Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials.
