A laser trapping-microspectroscopy technique combined with excitation energy transfer from a fluorescent cationic dye (Rhodamine B, RB+) to a non-fluorescent cationic dye (Malachite Green, MG+) was employed to study p...A laser trapping-microspectroscopy technique combined with excitation energy transfer from a fluorescent cationic dye (Rhodamine B, RB+) to a non-fluorescent cationic dye (Malachite Green, MG+) was employed to study pH effects on the diffusion coefficients of MG+ (D(MG+)) in single cation-exchange resin microparticles with the diameters of 16 μm. When RB+-pre-adsorbed resin particles were soaked in an aqueous MG+ solution, the RB+ fluorescence was quenched gradually with the soaking time. The time course of the quenching efficiency of RB+ by MG+ was then used to evaluate the D(MG+) value in the particle. The D(MG+) value increased from 1.1 × 10-11 to 4.3 × 10-11 cm2.s–1 on going the solu- tion pH value from 9 to 4. The results were explained reasonably by a Donnan electric potential model.展开更多
In the study of the mechanical properties of the erythrocytes (red blood cells-RBCs) the blood sample is commonly diluted in fluids that do not compromise the integrity of the cells. Fetal bovine serum (FBS), newborn ...In the study of the mechanical properties of the erythrocytes (red blood cells-RBCs) the blood sample is commonly diluted in fluids that do not compromise the integrity of the cells. Fetal bovine serum (FBS), newborn bovine serum (NBBS), and phosphate buffer (PBS) solution with a concentration that can provide the right osmotic pressure are fluids commonly used to dilute the blood samples in such studies. Here we have presented the effect of these fluids on the elastic properties of the RBCs that we studied using laser traps. Two laser traps are directly used to trap and deform the cell by exerting a force distributed on the entire cell. The relative changes in size of the cell are studied as a function of the applied force to investigate any effects on the mechanical deformability of RBCs when the cells are suspended in these fluids. The results have shown that the elasticity of the RBCs in the NBBS is not statistically different from the elasticity of the cells in the PBS solution;however the results for the elasticity of the cells in FBS are found to be significantly higher.展开更多
The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique re...The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constantdepth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit–Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic fields.Finally, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms.展开更多
We investigate femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles with different volume fractions and two-photon absorption(TPA)coefficients.Numerical simulations show that the hollo...We investigate femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles with different volume fractions and two-photon absorption(TPA)coefficients.Numerical simulations show that the hollow-core particles with low and high-volume fractions can easily be trapped and bounced by the tightly focused Gaussian laser pulses,respectively.Further studies show that the hollow-core particles with and without TPA can be identified,because the TPA effect enhances the radiation force,and subsequently the longitudinal force destabilizes the trap by pushing the particle away from the focal point.The results may find direct applications in particle sorting and characterizing the TPA coefficient of single nanoparticles.展开更多
We investigate the quantum motion of two ions stored in a Paul trap and interacting with a time-periodic laser field. In the pseudopotential approximation and large detuning condition, we find that the relative motion...We investigate the quantum motion of two ions stored in a Paul trap and interacting with a time-periodic laser field. In the pseudopotential approximation and large detuning condition, we find that the relative motion is independent of the laser field, but the exact centre-of-mass motion is closely related to the laser field. By adjusting the laser intensity and frequency, we can well control the quantum motion of the centre-of-mass. We illustrate some physical properties described by the centre-of-mass states, such as the squeezed coherent property, the widths and heights of the wavepackets of probability density, the classical-quantum correspondence, the resonance ladders of expectation energy and the transition probabilities between time-dependent quantum levels.展开更多
Beyond the Lamb-Dicke limit, this paper investigates the squeezing properties of the trapped ion in the travelling- wave laser. It shows that the squeezing properties of the trapped ion in the travelling-wave laser ar...Beyond the Lamb-Dicke limit, this paper investigates the squeezing properties of the trapped ion in the travelling- wave laser. It shows that the squeezing properties of the trapped ion in the travelling-wave laser are strongly affected by the sideband number k, the Lamb-Dicke parameter η and the initial average phonon number.展开更多
A single particle magneto-confined in a one-dimensional （1D） quantum wire experiences a harmonic potential, and imposing a sharply focused laser beam on an appropriate site shapes a δ potential. The theoretical inv...A single particle magneto-confined in a one-dimensional （1D） quantum wire experiences a harmonic potential, and imposing a sharply focused laser beam on an appropriate site shapes a δ potential. The theoretical investigation has demonstrated that for a sufficiently strong δ pulse the quantum motional stationary state of the particle is one of the eigenstates of the free harmonic oscillator, and it is determined by the site of the laser beam uniquely, namely a quantum state is admissible if and only if the laser site is one of its nodes. The numerical computation shows that all the nodes of the lower energy states with quantum numbers n ≤ 20, except the coordinate origin, are mutually different. So we can manipulate the multiphoton transitions between the quantum states by adjusting the position of the laser δ pulse and realize the transition from an unknown higher excitation state to a required lower energy state.展开更多
Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and ex...Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and exciting applications. In this paper, the radical 138Ba19F, as a promising candidate for laser cooling and magneto-optical trapping, is discussed in detail.The highly diagonal Franck-Condon factors between theX2∑＋1/2and A2∏1/2states are first confirmed with three different methods. Afterwards, with the effective Hamiltonian approach and irreducible tensor theory, the hypertine structure of theX2∑＋1/2state is calculated accurately. A scheme for laser cooling is given clearly. Besides, the Zeeman effects of the upper （ A2∏1/2）andlower（X2∑＋1/2）levels are also studied, and their respective g factors are obtained under a weak magnetic field. Its large g factor of the upper stateA2∏1/2is advantageous for magneto-optical trapping. Finally, by studying Stark effect of BaFin theX2∑＋1/2, we investigate the dependence of the internal effective electric field on the applied electric field. It is suggested that such a laser-cooled BaF is also a promising candidate for precision measurement of electron electric dipole moment.展开更多
We propose a novel scheme of optical confinement for atoms by using a concave grating reflector.The two-dimension grating structure with a concave surface shape exhibits strong focusing ability under radially polarize...We propose a novel scheme of optical confinement for atoms by using a concave grating reflector.The two-dimension grating structure with a concave surface shape exhibits strong focusing ability under radially polarized illumination.Especially,the light intensity at the focal point is about 100 times higher than that of the incident light.Such a focusing optical field reflected from the curved grating structure can provide a deep potential to trap cold atoms.We discuss the feasibility of the structure serving as an optical dipole trap.Our results are as follows.（i） Van der Waals attraction potential to the surface of the structure has a low effect on trapped atoms,（ⅱ） The maximum trapping potential is ~1.14 mK in the optical trap,which is high enough to trap cold ^87Rb atoms from a standard magneto-optical trap with a temperature of 120 μK,and the maximum photon scattering rate is lower than 1/s.（ⅲ） Such a microtrap array can also manipulate and control cold molecules,or microscopic particles.展开更多
文摘A laser trapping-microspectroscopy technique combined with excitation energy transfer from a fluorescent cationic dye (Rhodamine B, RB+) to a non-fluorescent cationic dye (Malachite Green, MG+) was employed to study pH effects on the diffusion coefficients of MG+ (D(MG+)) in single cation-exchange resin microparticles with the diameters of 16 μm. When RB+-pre-adsorbed resin particles were soaked in an aqueous MG+ solution, the RB+ fluorescence was quenched gradually with the soaking time. The time course of the quenching efficiency of RB+ by MG+ was then used to evaluate the D(MG+) value in the particle. The D(MG+) value increased from 1.1 × 10-11 to 4.3 × 10-11 cm2.s–1 on going the solu- tion pH value from 9 to 4. The results were explained reasonably by a Donnan electric potential model.
文摘In the study of the mechanical properties of the erythrocytes (red blood cells-RBCs) the blood sample is commonly diluted in fluids that do not compromise the integrity of the cells. Fetal bovine serum (FBS), newborn bovine serum (NBBS), and phosphate buffer (PBS) solution with a concentration that can provide the right osmotic pressure are fluids commonly used to dilute the blood samples in such studies. Here we have presented the effect of these fluids on the elastic properties of the RBCs that we studied using laser traps. Two laser traps are directly used to trap and deform the cell by exerting a force distributed on the entire cell. The relative changes in size of the cell are studied as a function of the applied force to investigate any effects on the mechanical deformability of RBCs when the cells are suspended in these fluids. The results have shown that the elasticity of the RBCs in the NBBS is not statistically different from the elasticity of the cells in the PBS solution;however the results for the elasticity of the cells in FBS are found to be significantly higher.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12104414,12122412,12104464,and 12104413)the China Postdoctoral Science Foundation(Grant No.2021M702955).
文摘The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constantdepth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit–Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic fields.Finally, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms.
基金financially supported by the National Natural Science Foundation of China(No.11774055)the Natural Science Foundation of Jiangsu Province(No.BK20171364)。
文摘We investigate femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles with different volume fractions and two-photon absorption(TPA)coefficients.Numerical simulations show that the hollow-core particles with low and high-volume fractions can easily be trapped and bounced by the tightly focused Gaussian laser pulses,respectively.Further studies show that the hollow-core particles with and without TPA can be identified,because the TPA effect enhances the radiation force,and subsequently the longitudinal force destabilizes the trap by pushing the particle away from the focal point.The results may find direct applications in particle sorting and characterizing the TPA coefficient of single nanoparticles.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10575034 and 10275023）, and the Science Foundation of the Laboratory of Magnetic Resonance and Atomic and Molecular Physics, China （Grant No T152504）.
文摘We investigate the quantum motion of two ions stored in a Paul trap and interacting with a time-periodic laser field. In the pseudopotential approximation and large detuning condition, we find that the relative motion is independent of the laser field, but the exact centre-of-mass motion is closely related to the laser field. By adjusting the laser intensity and frequency, we can well control the quantum motion of the centre-of-mass. We illustrate some physical properties described by the centre-of-mass states, such as the squeezed coherent property, the widths and heights of the wavepackets of probability density, the classical-quantum correspondence, the resonance ladders of expectation energy and the transition probabilities between time-dependent quantum levels.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘Beyond the Lamb-Dicke limit, this paper investigates the squeezing properties of the trapped ion in the travelling- wave laser. It shows that the squeezing properties of the trapped ion in the travelling-wave laser are strongly affected by the sideband number k, the Lamb-Dicke parameter η and the initial average phonon number.
基金Project supported by the National Natural Science Foundation of China （Grant No 10575034）, and the Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics of China （Grant No T152504）.
文摘A single particle magneto-confined in a one-dimensional （1D） quantum wire experiences a harmonic potential, and imposing a sharply focused laser beam on an appropriate site shapes a δ potential. The theoretical investigation has demonstrated that for a sufficiently strong δ pulse the quantum motional stationary state of the particle is one of the eigenstates of the free harmonic oscillator, and it is determined by the site of the laser beam uniquely, namely a quantum state is admissible if and only if the laser site is one of its nodes. The numerical computation shows that all the nodes of the lower energy states with quantum numbers n ≤ 20, except the coordinate origin, are mutually different. So we can manipulate the multiphoton transitions between the quantum states by adjusting the position of the laser δ pulse and realize the transition from an unknown higher excitation state to a required lower energy state.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91536218,11374100,10904037,10974055,11034002,and 11274114)the National Key Basic Research and Development Program of China(Grant No.2011CB921602)the Natural Science Foundation of Shanghai Municipality,China(Grant No.13ZR1412800)
文摘Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and exciting applications. In this paper, the radical 138Ba19F, as a promising candidate for laser cooling and magneto-optical trapping, is discussed in detail.The highly diagonal Franck-Condon factors between theX2∑＋1/2and A2∏1/2states are first confirmed with three different methods. Afterwards, with the effective Hamiltonian approach and irreducible tensor theory, the hypertine structure of theX2∑＋1/2state is calculated accurately. A scheme for laser cooling is given clearly. Besides, the Zeeman effects of the upper （ A2∏1/2）andlower（X2∑＋1/2）levels are also studied, and their respective g factors are obtained under a weak magnetic field. Its large g factor of the upper stateA2∏1/2is advantageous for magneto-optical trapping. Finally, by studying Stark effect of BaFin theX2∑＋1/2, we investigate the dependence of the internal effective electric field on the applied electric field. It is suggested that such a laser-cooled BaF is also a promising candidate for precision measurement of electron electric dipole moment.
基金supported by the National Natural Science Foundation of China(Grant Nos.11374100,91536218,and 11274114)the Natural Science Foundation of Shanghai Municipality,China(Grant No.13ZR1412800)
文摘We propose a novel scheme of optical confinement for atoms by using a concave grating reflector.The two-dimension grating structure with a concave surface shape exhibits strong focusing ability under radially polarized illumination.Especially,the light intensity at the focal point is about 100 times higher than that of the incident light.Such a focusing optical field reflected from the curved grating structure can provide a deep potential to trap cold atoms.We discuss the feasibility of the structure serving as an optical dipole trap.Our results are as follows.（i） Van der Waals attraction potential to the surface of the structure has a low effect on trapped atoms,（ⅱ） The maximum trapping potential is ~1.14 mK in the optical trap,which is high enough to trap cold ^87Rb atoms from a standard magneto-optical trap with a temperature of 120 μK,and the maximum photon scattering rate is lower than 1/s.（ⅲ） Such a microtrap array can also manipulate and control cold molecules,or microscopic particles.
