Search

An efficient route for detecting time-dependent acceleration (TDA) is performed by employing electromechanically induced phononic sidebands in coupled frequency-mismatched electromechanical resonators. Based on the effects of difference frequency mixing and cascaded phonon-scattering in the electromechanical system, the nonlinear responses of normal and anomalous phononic sidebands are generated and enhanced in the strong inter-modal coupling regime. In the detection scheme, the information of TDA can be delivered to the spectral responses of acceleration-induced sidebands (AISs) since there is the piezoelectric coupling between the electromechanical resonators and a test mass that perceives external acceleration. Additionally, the amplitude of TDA could be separately detected by observing the amplitude variation of AISs, while the variation period of TDA could be read by monitoring the frequency of the prominent peak in the AIS signals. The distinctive nature of the electromechanical system in the environment of the cryogenic cooling enables an acceleration resolution of 12 µg (g = 9.8 m s−2) and a frequency resolution of 0.06 Hz.

The electronic, optical, and photocatalytic properties of Au-adsorbed MoSi2N4 systems are predicted by first-principles calculations. Electronic structure analysis shows that the band gap is reduced from 1.89 eV (intrinsic MoSi2N4) to 0 eV (MoSi2N4–9Au). Calculation results of density of states indicate that the valence band edge is mainly contributed by the Mo 4d state, whereas the conduction band edge is contributed by both the Mo 4d and Si 3p states. As the number of adsorbed Au atoms is increased, the absorption coefficient increases from 3.0 × 104 cm−1 to 5.6 × 104 cm−1, meaning that more photons can be absorbed. Indeed, Au-adsorbed MoSi2N4 monolayer shows greater potential for applications such as water splitting and CO2 reduction based on redox potential analysis. The Au-adsorbed MoSi2N4 structures can effectively change the properties of materials, offering great potential in different fields.

We investigate the coherent control of the transmission spectrum in a cavity magnetomechanical system consisting of microwave photon, magnon, and phonon modes, where the microwave cavity is driven by a strong pump field and a weak probe field, and the magnon is driven by a weak microwave source. Different from a single transparency window in the absence of the phonon–magnon interaction, two transparency windows and three absorption dips can be observed in the presence of the phonon–magnon interaction, which originates from the joint interaction of phonon–magnon and photon–magnon. In addition, two absorption dips located at both sides of the central absorption dip can be modulated asymmetrically into amplification and absorption by varying the magnetic field amplitude of the magnon driving field. Interestingly enough, the relative phase of applied fields could have profound effects on both the transmission spectrum and the group delay of the output field by choosing the appropriate magnetic field amplitude of the magnon driving field. The transmission group delay can be switched between positive to negative and vice versa by adjusting the relative phase between the applied fields. The present results illustrate the potential to utilize the relative phase for controlling the microwave signal in the cavity magnomechanical system, as well as guidance in the design of information transduction and quantum sensing.

We propose a theoretical scheme to coherently control the transport of a single electron in an asymmetric double-quantum-dot system. The single-electron transport originates from the intrinsic interplay between the externally applied few-cycle pulse and the inter-dot tunneling. Solving the equations of motion for dot-density matrix, we reveal numerically that the current exhibits a significant dependence on the carrier-envelope phase (CEP) of the few-cycle pulse, which is similar to the magnetic flux controlled coherent transport in an Aharnov–Bohm (AB) interferometer. As a result, by varying the CEP of the pulse one can suppress or enhance the current either instantaneously or periodically. Our results illustrate the potential to utilize few-cycle pulses for excitation in quantum dot systems through the CEP control, as well as a guidance in the design for possible experimental implementations.

We theoretically study the coherent transport of a single electron between the ground states of a double coupled quantum dot structure. The coherent transport is externally controlled by applying a few-cycle pulse with an adjustable carrier-envelope phase (CEP). By simulating numerically, it is shown that there exhibits a strong dependence of electron transport on the CEP and on the arrival time of few-cycle pulse. We provide a simple analytical description for this phenomenon by approximating the quantum dot structure as a three-level Λ-type system. These results also illustrate the potential of utilizing excitation in coupled quantum dots as a means of measuring the CEP of few-cycle pulses.

We investigate the effects of geometrical and structural disorders on perfectly asymmetric diffraction (PAD) in Raman-Nath regime. The two types of disorders are realized by introducing random fluctuations in the position and width of one-dimensional (1D) driven atomic lattices. Raman-Nath diffraction is modified differently with respect to the geometrical and structural disorders. It is shown that the PAD is observed with a certain strength range of geometrical disorder, exceeding which it can be destroyed, while the PAD is rather robust against structural disorder. The different behaviors originate from the disorder-induced random variations of the spatial phase shifts of the standing-wave (SW) coupling field and atomic lattices with Gaussian profile. Furthermore, we find that, in the presence of geometrical disorder, the PAD is more susceptible to correlated disorder than to uncorrelated disorder. Our scheme may be useful for understanding the effects of disorder on the diffraction of light and matter waves in disordered potentials..

Here, on a platform of two split-ring resonator (SRR) disks in the microwave regime, we have numerically and experimentally investigated the coupling of toroidal localized spoof surface plasmons (LSSPs). The coupling effect is investigated both theoretically and experimentally. We observe that magnetic dipole coupling exists in the toroidal LSSPs coupling and causes a rearrangement of the toroidal LSSPs, which suppresses the propagation of toroidal LSSPs. To realize the propagation of toroidal LSSPs, we introduce conductive coupling into the SRR disks. The conductive coupling can correct magnetic dipole coupling and enhance toroidal LSSPs coupling. Both numerical simulations and experiments are in good agreement. The toroidal LSSPs can be effectively propagated, even in the three right-angle-bent SRR disks. This study paves the way toward a better understanding of toroidal LSSPs coupling and finds many applications in the transfer of electromagnetic energy using toroidal moments.

The giant enhancement of Kerr nonlinearity in a four-level inverted-Y atomic system is investigated theoretically. Compared with that generated in a generic three-level system, the Kerr nonlinearity can be enhanced by several orders of magnitude with vanishing linear absorption. The physical mechanism leading to the giant enhancement of Kerr nonlinearity is also discussed.

We propose a scheme for high-precision two-dimensional (2D) atom localization via the four-wave mixing (FWM) in a four-level double- atomic system. Due to the position-dependent atom-field interaction, the 2D position information of the atoms can be directly determined by the measurement of the normalized light intensity of output FWM-generated field. We further show that, when the position-dependent generated FWM field has become sufficiently intense, efficient back-coupling to the FWM generating state becomes important. This back-coupling pathway leads to competitive multiphoton destructive interference of the FWM generating state by three supplied and one internally generated fields. We find that the precision of 2D atom localization can be improved significantly by the multiphoton destructive interference and depends sensitively on the frequency detunings and the pump field intensity. Interestingly enough, we show that adjusting the frequency detunings and the pump field intensity can modify significantly the FWM efficiency, and consequently lead to a redistribution of the atoms. As a result, the atom can be localized in one of four quadrants with holding the precision of atom localization.

We investigate the enhancement of Kerr nonlinearities in an asymmetric coupled double quantum-well (CQW) by analyzing the nonlinear optical response. With the consideration of real parameters in AlGaAs-based CQWs, we indicate the possibility to obtain the giant Kerr nonlinearities with the cancellation of linear absorption simultaneously. We also reveal both analytically and numerically that under appropriate conditions a probe field with very low intensity can evolve into a stable shape-preserving waveform that propagates with a slow group velocity. The stability of such slow optical solitons is also demonstrated numerically.

We propose and analyze an efficient scheme for suppressing the absorption of a weak probe field based on intersubband transitions in a four-level asymmetric coupled quantum well (CQW) driven coherently by a probe laser field and a control laser field. We study the steady-state process analytically and numerically, and our results show that the probe absorption can be completely eliminated under the condition of Raman resonance (i.e. two-photon detuning is zero). Besides, we can observe one transparency window without requiring one- or two-photon detuning to exactly vanish. This investigation may provide a possible scheme for EIT in solids by using the CQW.

We study the spectrum of ultracold atoms on the honeycomb lattice under a constant effective magnetic field. In the tight-binding approximation, we derived the generalized Harper's equations and numerically calculate the spectrum, which has a fractal structure. For the cases with and without the next-nearest-neighbor tunneling, the graphs of spectra have different symmetries. Comparing the symmetries of the graphs of spectra, we find that next-nearest-neighbor tunneling induces symmetry breaking of the graph of spectrum.

We perform a time-dependent analysis of continuous wave (cw) four-wave mixing (FWM) in InGaAs/AlAs coupled double quantum well (CDQW) structures via intersubband transitions. By using the coupled Schrodinger-Maxwell approach, we obtain the corresponding explicit analytical expressions for the input probe and FWM-generated signal fields. We calculated the dependencies of the efficiency of the FWM-generated fields on cw pump fields and the depths of penetration into the CDQW sample. Such a nonlinear optical process may be used to generate coherent short-wavelength radiation efficiently in the CDQW solid state system.

We show that a giant Kerr nonlinearity with a relatively large cross phase modulation (CPM) phase-shift can be used for realizing polarization quantum phase gate based on the nonlinear optical response in a coupled semiconductor double quantum well (SDQW) structure via intersubband transitions.

In this letter, a efficient scheme is proposed for the quantum secret encryption and decryption implementation for quantum secret sharing protocol with trapped ions in thermal motion, in which the effective Hamiltonian does not involve the external degree of freedom and thus the scheme is insensitive to the external state, allowing it to be thermal state. The proposed scheme requires no auxiliary states to assist intermediate atomic transitions and conditional quantum dynamics for quantum phase flip and quantum state diffusion. Besides, secret transmission using entanglement swapping also has been presented.

We propose a practical scheme for implementing two-dimension quantum dense coding (QDC) between three parties through manipulating three ions confined in microtraps addressed by microwaves and assisted by a magnetic field gradient. The ions in our scheme are not required to be strictly cooled to the vibrational ground state because single-qubit and multi-qubit operations are made via Ising terms, in which the vibrational modes of the ions remain unchanged throughout the scheme, rendering our scheme robust to the heating of the ions. We also present the detailed steps and parameters for implementing the three-party QDC experimentally and show that the proposed scheme is within the current techniques of ion-trap experiments., Comment: 6 pages, 2 figures, accepted by J. Phys. B: At. Mol. Opt. Phys

We study ultrafast excitonic population inversion resulting from the interaction of a semiconductor quantum dot (SQD) with localized surface plasmons. The plasmonic enhanced fields are generated when a metallic nanoparticle (MNP) is subject to a nonlinear chirped few-cycle pulse train. By numerically solving the time-dependent Bloch equations beyond the rotating-wave approximation, we show that the complete population inversion can be achieved for small interparticle distance and the dynamic in population inversion exhibits a steplike transition between absorption and amplifying. This phenomenon can be exploited as an all-optical ultrafast switching device. Moreover, the final state of population inversion is shown to be modified significantly with the interparticle distances, which is not only robust against the variation of probe pulse parameters but also suggests a straightforward method for measuring the interparticle distances via probing the final populations.

In this letter, a procedure is proposed for reconstructing the motional quantum state of N trapped ions. Unlike other previous schemes, the present scheme works in the dispersive regime in the presence of dissipation. In our scheme, we show that it is possible to directly measure the quasiprobability distribution function corresponding to the motional coherent state in a trapped-ion system subjected to dissipation. We also provide an example of a motional Schrödinger cat state reconstruction to exemplify our procedure.

We present an alternative scheme to prepare entangled states of multiple trapped ions in thermal motion. In this scheme the vibrational degrees of freedom are only regarded as intermediate states and the ions exchange energy via the mediation of the vibration of the vibrational mode in coupling processes. The scheme is insensitive to both the initial vibrational state and heating if the system remains in the Lamb–Dicke regime. Since the effective Rabi frequency has a small dependence on the vibrational quantum number, the heating will have no direct effect on the internal state evolution. The scheme can also be used for the storage of entangled states.

We show the formation of slow bistable solitons in a lifetime broadened three-state atomic medium with strong field excitation. We demonstrate, both analytically and numerically, that slow bistable solitons with low peak intensity can exist under appropriate conditions. This work may provide new experimental evidence of bistability of light solitons.

We proposed a scheme to generate a multi-component squeezed coherent states with arbitrary coefficients on a line in phase space for multiple trapped ions radiated by a single standing-wave laser whose carrier frequency is tuned to the ions transition. In the scheme each ion does not need to be exactly positioned at the node of the standing wave. Furthermore, our scheme may allow the generation of a multi-component squeezed coherent states with large mean phonon number in a fast way by choosing a suitable laser intensity, which is important in view of de-coherence processes.

With a detailed series of spontaneous optical pattern formations, we reveal the existence of thermodynamical properties in nonlinear optical systems by defining the configurational entropy from the measured patterns. A phase diagram for pattern transitions in the form of stripes, reoriented stripes, hexagons, and spots is reported experimentally and theoretically for incoherent beams in non-instantaneous anisotropic photorefractive crystals, with demonstrations in the boundary of mixed-phase states. Emergence of optical pattern transitions is shown to occur at the local minimum values of effective optical temperature, and accompanied with the change of chemical potentials.

Considering two-level media in the array of weakly coupled nano-cavities, we reveal a variety of dynamical regimes, such as diffusion, self-trapping, soliton, and breathers for the wave-packets in the presence of photon tunneling processes between the next-nearest cavities. We focus our attention on the low branch (LB) bright polariton soliton formation, due to the two-body polariton-polariton scattering processes. When detuning frequency is manipulated adiabatically, the low-branch lattice polariton localized states, i.e., that are solitons and breathers evolving between photon-like and matter-like states, are shown to act as carriers for spatially distributed storage and retrieval of optical information., Comment: 10 pages, 7 figures

We study the control of high-precision three-dimensional (3D) atom localization by measuring the population of the excited state in a ladder-type three-level atomic system driven by a weak probe field and a control field, together with three mutually perpendicular standing-wave fields. We find that the precision of 3D atom localization in volumes depends sensitively on the frequency detuning of the probe field and the intensity of the control field. Most importantly, we show that adjusting the phase shifts associated with the standing-wave fields leads to a redistribution of the atoms and a significant change of the atomic coherence, so that the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength.

We propose and analyze an effective scheme to generate hyper-Raman scattering via inhibiting electromagnetically induced transparency (EIT) in a monolayer graphene under a magnetic field. By solving the Schrödinger-Maxwell formalism, we derive explicitly analytical expressions for linear susceptibility, nonlinear susceptibility, and generated Raman electric field under the steady-state condition. Based on dressed-state theory, our results show a competition between EIT and hyper-Raman scattering, and the hyper-Raman process is totally dominant when multiphoton destructive interference is completely suppressed.

We theoretically investigate the simultaneous formation and stable propagation of slow optical soliton pairs in semiconductor quantum dots with a four-level biexciton-exciton cascade configuration. Owing to the destructive interference set up by two continuous wave control fields that couple to a biexciton state, the linear as well as nonlinear dispersion can be dramatically enhanced simultaneously with the absorptions of two weak probe fields being almost suppressed. These results reveal that the detrimental distortions of the two weak-pulsed probe fields due to dispersion effects can be well balanced by the self-phase modulation effect under very low input light intensity, which leads to the slow temporal optical soliton pairs with matched group velocity and amplitude. We also show that the propagation of slow optical solitons can be strongly modified by the biexciton coherence.

We propose a novel scheme to simulate and observe massless Dirac fermions with cold atoms in a square optical lattice. A U(1) adiabatic phase is created by two laser beams for the tunneling of atoms between neighbor lattice sites. Properly adjusting the tunneling phase, we find that the energy spectrum has conical points in per Brillouin zone where band crossing occurs. Near these crossing points the quasiparticles and quasiholes can be considered as massless Dirac fermions. Furthermore, the anisotropic effects of massless Dirac fermions are obtained in the present square lattice model. The Dirac fermions as well as the anisotropic behaviors realizeded in our system can be experimentally detected with the Bragg spectroscopy technique.

We study the low-intensity light pulse propagation through an asymmetric double quantum well via Fano-type interference based on intersubband transitions. The propagation of the pulse across the quantum well is studied analytically and numerically with the coupled Maxwell-Schr\"odinger equations. We show the generation of ultraslow bright and dark optical solitons in this system. Whether the solitons are dark and bright can be controlled by the ratio of dipole moments of the intersubband transitions. Such investigation of ultraslow optical solitons in the present work may lead to important applications such as high-fidelity optical delay lines and optical buffers in semiconductor quantum wells structure.

A scheme of enhanced four-wave mixing (FWM) signal is exploited in graphene under an external magnetic field via multiphoton quantum destructive interference. By solving the coupled Schrodinger–Maxwell formalism, a time-dependent analysis performs the integrated analytical expressions of the input probe pulse and generated FWM field. Taking into account the tunable optical transition frequency between the Landau levels (LLs) in graphene, it is found that the generated FWM signal in the infrared region can be significantly enhanced and its efficiency is nearly . As a result, the proposed magnetised graphene system may provide a striking potential for generating long-wavelength radiation.

transparency [Phys. Rev. B 75, 184423 (2007)] Xiao-Tao Xie, Weibin Li, Jiahua Li, Wen-Xing Yang, Anming Yuan, and Xiaoxue Yang Received 24 May 2007; published 22 June 2007 DOI: 10.1103/PhysRevB.75.219903 PACS number s : 75.50.Xx, 43.25. y, 42.50.Gy, 99.10.Cd Equation 21b on page 5 is wrong. The correction is ũ= −2c2 c4 sech c2Z , c2 0, c4 0, c0=0. The function “sinh” should be replaced by “sech.” This change does not affect the conclusions of the paper. PHYSICAL REVIEW B 75, 219903 E 2007

We have studied the propagation properties of transverse acoustic wave in molecular magnets in the presence of a strong ac magnetic field. Due to quantum interference introduced by the strong electromagnetic field, the acoustic wave can propagate without absorption under appropriate conditions, which is a direct result of electromagnetically induced transparency effect. Meanwhile, the nonlinear effects should be considered in the propagation of the acoustic wave because electromagnetic induction transparency effect can greatly enhance nonlinear effects. The transverse acoustic wave propagation equation including nonlinear effects in molecular magnets has been investigated and the corresponding accurate analytic solutions have been obtained. We believe that our research may promote the understanding of the acoustic wave's properties in molecular magnets.

We propose an efficient four-wave mixing (FWM) scheme in asymmetric semiconductor quantum wells (SQWs) via two-photon resonance. By using the coupled Schrodinger–Maxwell formalism, we derive explicitly the corresponding analytical expressions of the inter-probe pulse and generated FWM field in the linear regime under the steady-state condition. With the aid of cross coupling between one ground state and two closely adjacent excited states, the efficiency of the generated FWM field is found to be significantly enhanced, up to 60%. More interestingly, a wide region of the maximum FWM efficiency is demonstrated as the ratio of transition dipole moments is within the values ranging from 1.1 to 1.3, which can be maintained for a certain propagation distance (i.e. 100 μm).

In this paper, we analyze theoretically the optical steady behavior in GaAs quantum well structure which interacts with a single elliptically polarized field (EPF) and a π-polarized probe field. Due to the existence of the robust nonradiative coherence, we demonstrate that the controllable optical steady behavior including multi-stability (OM) and optical bistability (OB) can be obtained. More interestingly, our numerical results also illustrate that tuning the phase difference between two components of polarized electric field of the EPF can realize the conversion between OB and OM. Our results illustrate the potential to utilize the optical phase for developing the new all-optical switching devices, as well as a guidance in the design for possible experimental implementations.

We investigate the light propagation and dynamical control of a weak pulsed probe field in asymmetric double quantum wells via Fano interference, which is caused by tunneling from the excited subbands to the same continuum. Our results show that the system can produce anomalous and normal dispersion regions with negligible absorption by choosing appropriate coupling strength of the tunneling and the Fano interference. Interesting enough, the dispersion can be switched between normal and anomalous by adjusting the relative phase between the pulsed probe and coherent control fields owing to the existence of the perfectly Fano interference. Thus, the relative phase can be regarded as a switch to manipulate light propagation with subluminal or superluminal. The temporal and spatial dynamics of the pulsed probe field with hyperbolic secant envelope are analyzed.

We investigate the probe absorption properties in an asymmetric coupled double quantum-well structure for both the transient and steady-state processes. Beyond the rotating-wave approximation, we directly simulate the transient dynamics with the density-matrix equations. The probe absorption is found to be completely eliminated under the condition of two-photon resonance, without requiring the one-photon resonance condition. More interestingly, our results show that the absorption properties can be tuned by changing the tunnelling barrier.

By analyzing the nonlinear optical response in an asymmetric coupled double quantum well structure based on the intersubband transitions, we show that a giant Kerr nonlinearity with a relatively large cross-phase modulation coefficient can be used to produce efficient photonphoton entanglement and implement an all-optical two-qubit quantum polarization phase gate. We also demonstrate that such photon-photon entanglement is practically controllable and may facilitate more practical applications in all-optical quantum information and computation.