Robust generation of qutrit entanglement via adiabatic passage of dark states

We propose a scheme for the deterministic generation of qutrit entanglement for two atoms trapped in an optical cavity. Taking advantage of the adiabatic passage, the operation is immune to atomic spontaneous emission as the atomic excited states are never populated; under certain conditions, the probability that the cavity is excited is negligible. We also study the influences of the dissipation due to the atomic spontaneous emission and cavity decay.

Dark states and Aharonov-Bohm oscillations in multi-quantum-dot systems

We study the formation of dark states and the Aharonov-Bohm effect in symmetrically/asymmetrically coupled three- and four-quantum-dot systems. It is found that without a transverse magnetic field, destructive interference can trap an electron in a dark state. However, the introduction of a transverse magnetic field can disrupt the dark state, giving rise to oscillation in current. For symmetrically structured quantum-dot systems, the oscillation has a period of one flux quanta. But for asymmetrically structured dot systems, the period of oscillation is halved. In addition, the dephasing due to charge noise also blocks the formation of dark states, while it does not change the period of oscillation.

Two-Photon Excited State Dynamics of Dark Rydberg and Bright Valence States in Furan

Two-photon absorption in systems with parity permits access to states that cannot be directly prepared by one-photon absorption. Here we investigate ultrafast internal conversion （IC） dynamics of furan by using this strategy in combination with femtosecond time-resolved photoelectron imaging. The dark Rydberg S1 and bright valence S2 states are simultaneously excited by two photons of 405 nm, and then ionized by two photons of 800nm. The IC from S2 to S1 is clearly observed and extracted from the time dependence of the higher photoelectron kinetic energy （PKE） component. More importantly, the internal conversions to hot So from directly-prepared S1 and secondarily-populated S1 are unambiguously identified by the time-dependence of the lower PKE component. The average lifetime of the S2 and S1 states is measured to be 29 fs. The internal conversions of S2 to S1, S1 to hot So occur on estimated timescales of 15.4 fs and 38 fs, respectively.

Dark energy from logarithmically modified gravity and deformed Coleman-Weinberg potential

Recent astrophysical measurements strongly suggest the existence of a missing energy component dubbed dark energy that is responsible for the current accelerated expansion of the universe.A new class of modified gravity theory is introduced which yields a universe accelerating in time and dominated by dark energy.The new modified gravity model constructed here concurrently includes a Gauss-Bonnet invariant term,barotropic fluid with a time-dependent equation of state parameter,a Coleman-Weinberg（CW） potential-like expression V（φ） =ξφm lnφn and a new Einstein-Hilbert term f（R,φ） =E（φ） R which depends on both the scalar curvature and the scalar fieldφthrough a generic logarithmic function E（φ） =lnφ.Here m and n take different values from the standard CW potential andξis a real parameter. It was shown that the presence of these terms provides many useful features which are discussed in some detail.

Instability, adiabaticity, and controlling effects of external fields for the dark state in a homonuclear atom tetramer conversion system

In the present paper, we investigate the instability, adiabaticity, and controlling effects of external fields for a dark state in a homonuclear atom-tetramer conversion that is implemented by a generalized stimulated Raman adiabatic passage. We analytically obtain the regions for the appearance of dynamical instability and study the adiabatic evolution by a newly defined adiabatic fidelity. Moreover, the effects of the external field parameters and the spontaneous emissions on the conversion efficiency are also investigated.

Dynamical instability and adiabatic evolution of the atom-homonuclear-trimer dark state in a condensate system

This paper investigates the dynamical instability and adiabatic evolution of the atom homonuclear-trimer dark state of a condensate system in a stimulated Raman adiabatic passage aided by Feshbach resonance. It obtains analytically the regions for the appearance of dynamical instability caused by the interparticle interactions. Moreover, the adiabatic property of the dark state is also studied in terms of a newly defined adiabatic fidelity. It shows that the nonlinear collisions have a negative effect on the adiabaticity of the dark state and hence reduce the conversion efficiency.

Linear instability and adiabaticity of a dark state during conversion of two species of fermionic atoms to stable molecules

In the present paper, we investigate the linear instability and adiabaticity of a dark state during conversion of two species of fermionic atoms to stable molecules through the stimulated Raman adiabatic passage aided by Feshbach resonance. We analytically obtain the regions for the appearance of linear instability. Moreover, taking 40K and 6Li atom molecule conversion systems as examples, we give the unstable regions numerically. We also attempt to obtain the adiabatic criterion for this nonlinear system with classical adiabatic dynamics and study the adibaticity of the dark state with the adiabatic condition.

Dynamical instability of the dark state in the conversion of Bose-Fermi mixtures into stable molecules

In this paper, we investigate the dynamical instability of the dark state in the conversion of Bose-Fermi mixtures into stable molecules through a stimulated Raman adiabatic passage aided by Feshbach resonance. We analytically obtain the regions where the dynamical instability appears and find that such instability in the Bose-Fermi mixture system is caused not only by bosonic interparticle interactions but also by Pauli blocking terms, which is different from the scenario of a pure bosonic system where instability is induced by nonlinear interparticle collisions. Taking a 40K-87Rb mixture as an example, we give the unstable regions numerically.

Constraining Equation of State of Dark Matter:Including Weak Gravitational Lensing

Usually the equation of state （EoS） of dark matter is zero when it is cold, however there exists the possibility of a （effective） nonzero EoS of dark matter due to its decay and interaction with dark energy. In this work, we try to constrain the EoS of dark matter/JAdm using the currently available cosmic observations which include the geometrical and dynamical measurements. For the geometrical measurements, the luminosity distance of type Ia supernovae, the angular diameter distance and comoving sound horizon from baryon acoustic oscillations and the cosmic microwave background radiation will be employed. The data points from the redshift-space distortion and weak gravitational lensing will be taken as dynamical measurements. Using the Markov chain Monte Carlomethod, we obtain a very tight constraint on the-EoS of dark matter：wdm=0.0000532 ＋0.000692＋0.00136＋0.00183 -0.000686-0.00136-0.00177.

Manipulation of multiple electromagnetically induced two-photon transparency in a six-level atomic system

In the five-level K-type atomic system, by using another control field to couple the excited level of the coupling transition to the sixth higher excited level, a six-level atomic system is constructed. In this system, the multiple electromagnetically induced two-photon transparency has been investigated. What is more, if choosing the parameters of the control fields properly the triple transparency window will reduce to a double one which means that the multiple electromagnetically induced two-photon transparency can be manipulated in this system. The physical interpretation of these phenomena is given in terms of the dressed states and the dark states.

Quantum Entanglement of Two Flux Qubits Induced by an Auxiliary SQUID

We revisit a theoretical scheme to create quantum entanglement of two three-level superconducting quantuminterference devices (SQUIDs) with the help of an auxiliary SQUID.In this scenario,two three-level systems are coupledto a quantized cavity field and a classical external field and thus form dark states.The quantum entanglement can beproduced by a quantum measurement on the auxiliary SQUID.Our investigation emphasizes the quantum effect of theauxiliary SQUID.For the experimental feasibility and accessibility of the scheme,we calculate the time evolution of thewhole system including the auxiliary SQUID.To ensure the efficiency of generating quantum entanglement,relationsbetween the measurement time and dominate parameters of the system are analyzed according to detailed calculations.

The bright and dark photon number states in Young’s interference experiment

In this paper, we derive the bright and dark photon number states for spatial interference of two or more light beams and succeed in the explanation of Young's interference experiment, and also achieve a better comprehension of the well known comment of Dirac 'each photon only interferences with itself'. Prom the fully quantum point of view, the origin of the interference fringes consists in the mode transformation and the detection of double-slit states.

Dark state atoms trapping in a magic-wavelength optical lattice near the nanofiber surface

We report the experimental realization of dark state atoms trapping in a nanofiber optical lattice.By applying the magicwavelength trapping potentials of cesium atoms,the AC Stark shifts are strongly suppressed.The dark magneto-optical trap efficiently transfers the cold atoms from bright (6S_(1/2),F=4) into dark state (6S_(1/2),F=3) for hyperfine energy levels of cesium atoms.The observed transfer efficiency is as high as 98%via saturation measurement.The trapping lifetime of dark state atoms trapped by a nanofiber optical lattice is also investigated,which is the key element for realizing optical storage.This work contributes to the manipulation of atomic electric dipole spin waves and quantum information storage for fiber networks.

Coherent excitation transfer via the dark-state channel in a bionic system

Light absorption and energy transfer were studied in a bionic system with donors and an acceptor.In the optimal case of uniform couplings,this seemingly complicated system was reduced to a three-level L-type system.With this observation,we showed that the efficiency of energy transfer through a dark-state channel,which is free of the spontaneous decay of the donors,was dramatically improved.After the overall average transfer time was evaluated,it was revealed that the time required for transfer through this channel was not optimal.To find the optimal parameters for the present system,we defined a new quantity,output power,which characterizes the average mean output of the whole transfer process.We estimated the optimal parameters of the system to achieve the maximum output power.The splitting behaviour of the maximum power may be used to explain the phenomenon of photosynthetic systems primarily absorbing two colours of light.

Modification of laser-induced state in atomic attosecond transient absorption by the XUV pulse pair

Attosecond transient absorption(ATA)has been developed as an all-optical technique for probing electron dynamics in matter.Here we present a scheme that can modify the laserinduced state and the corresponding ATA spectrum via excitation by a pair of XUV attosecond pulses and by a time-delayed mid-infrared(MIR)laser probe.Different from the scheme of the electronic excitation by a single XUV attosecond pulse,the application of a pair of XUV pulses provides extra degrees of freedom,such as the time delay and the intensity ratio between two XUV pulses,which make it possible to adjust the pump process,resulting in the modification of the ATA spectrum.We show that by varying the time delay between the two XUV pulses,the population of the dark state and the ATA spectrum of the laser-induced state have periodic modulations.We also demonstrate that the peak of the ATA spectrum of the laser-induced state appears at a fixed time delay between the XUV pair and the MIR laser when the intensity ratio is large,and it changes with the time delay when the intensity ratio is small,which can be related to either one of two peaks in the population of the dark state.

Simulation of EOM-based frequency-chirped laser slowing of MgF radicals

Here we propose a scheme to slow MgF molecules by using EOM-based frequency-chirped radiation pressure slowing.The scheme well addresses the need for a rapid chirp rate while light molecules are being laser slowed,whose scattering rate and recoil velocity are large.Two EOMs are used to compensate the rapidly changing Doppler shifts arised from the movement of molecules,and to cover the hyperfine energy structure of MgF,respectively.Based the scattering rate maps calculated from an optical Bloch equation model,individual molecule trajectories are simulated by using a semi-classical three-dimensional Monte Carlo approach.We show how the modulation configuration of EOM and the magnetic field influence the slowing results.The study shows that a cryogenic buffer gas-cooled MgF beam source is possible to be slowed down with a number of∼1.4×10^(6)–10^(7),and the final forward speed peaks at∼10 m/s near the capture velocity of a molecular MOT.

What are Exciting in Laser Science

Recent advances in selected areas of laser science are briefly reviewed. They include laser technology, coherent control of quantum systems by lasers, X ray generation by ultrashort high intensity laser pulses, and laser spectroscopic studies of surface catalysis in real environment.