Parameter accuracy analysis of weak-value amplification process in the presence of noise

We theoretically introduce the statistical uncertainty of photon number and phase error to discuss the precision of parameters to be measured based on weak measurements. When the photon counting scheme is used, we discuss the relative accuracy of the system in the presence of phase error by using the orthogonal and nonorthogonal pre-and postselected states, respectively. When using the measurement scheme of pointer shift, we discuss the measurement accuracy in the presence of phase error, pointer resolution, and statistical uncertainty. These results give a guide way to get the smallest relative precision and deepen our understanding about weak measurement.     

Exciton emission dynamics in single InAs/GaAs quantum dots due to the existence of plasmon-field-induced metastable states in the wetting layer

A very long lifetime exciton emission with non-single exponential decay characteristics has been reported for single InA-s/GaAs quantum dot(QD) samples,in which there exists a long-lived metastable state in the wetting layer(WL)through radiative field coupling between the exciton emissions in the WL and the dipole field of metal islands.In this article we have proposed a new three-level model to simulate the exciton emission decay curve.In this model,assuming that the excitons in a metastable state will diffuse and be trapped by QDs,and then emit fluorescence in QDs,a stretchedlike exponential decay formula is derived as I(t)=At~(β-1)e~(-(rt)β),which can describe well the long lifetime decay curve with an analytical expression of average lifetime     

Measurement-device-independent quantum dialogue

Recently, measurement-device-independent quantum secure direct communication schemes were proposed by Niu et al. [Sci. Bull. 63 1345(2018)] and Zhou et al. [Sci. China-Phys. Mech. Astron. 63 230362(2020)]. Inspired by their ideas,in this paper, a measurement-device-independent quantum dialogue protocol based on entanglement is designed and proven to be secure. The advantage of this scheme is that it can not only allow two communicators to transmit secret messages between each other, making the application scenarios more extensive, but can also eliminate all the security loopholes related to the measurement device and information leakage. In terms of experimental implementation, the scheme mainly involves the preparation of entangled states, the preparation of single photons, quantum storage, Bell measurement and other technologies, all of which are mature at present, therefore, the scheme is feasible by using current technologies.     

Coexistence and fluctuations phenomena with Davidson-like potentials in quadrupole-octupole deformed nuclei

The energy spectra of three types of two-dimensional potentials(we will call them‘Davidson-like potentials’(DLPs)),characterized by four minima separated by barriers,are investigated.The predictions for spectra and wave functions are obtained by using the nine-point finite-difference method.For these potentials,with the existence of a single configuration,a transition of spectra,as a function of barrier height,is covered from tunneling splitting modes to fluctuations phenomena,with equal peaks wave functions,crossing to the spectra of purely anharmonic oscillator potentials(AOPs).A different type of phase transition occurs when two(or more)configurations coexist.With the change of the parameters,a transition of spectra is covered from coexistence phenomena of two distinct quantum tunneling modes to fluctuations phenomena,with unequal peaks wave functions,crossing to the spectra of purely AOPs.Using DLPs,a particular application of the coherent quadropole-octupole model to describe energy bands with alternating parity of the nuclei¹⁰⁰Mo,^146,148Nd,^148,150Sm,²²⁰Ra,^220,222Rn,and^220,222Th is presented.The global parametrization of the model for the selected nuclei is achieved.     

Improvement on the manipulation of a single nitrogen-vacancy spin and microwave photon at single-quantum level

It remains a great challenge to realize direct manipulation of a nitrogen-vacancy(NV) spin at the single-quantum level with a microwave(MW) cavity. As an alternative, a hybrid system with the spin–phonon–photon triple interactions mediated by a squeezed cantilever-type harmonic resonator is proposed. According to the general mechanical parametric amplification of this in-between phonon mode, the direct spin–phonon and photon–phonon couplings are both exponentially enhanced, which can even further improve the coherent manipulation of a single NV spin and MW photon with a higher efficiency. In view of this triple system with enhanced couplings and the additional sideband adjustable designs, this scheme may provide a more efficient phonon-mediated platform to bridge or manipulate the MW quantum and a single electron spin coherently. It is also hoped to evoke wider applications in the areas of quantum state transfer and preparation,ultrasensitive detection and quantum nondestructive measurement, etc.     

Quantifying entanglement of two-qubit Werner states

In this article, we introduce a framework for entanglement quantification of photon pairs represented by two-qubit Werner states. The measurement scheme is based on the symmetric informationally complete POVM. To make the framework realistic, we impose the Poisson noise on the measured two-photon coincidences. For various settings, numerical simulations were performed to evaluate the efficiency of the framework.     

Effects of an anisotropic parabolic potential and Coulomb’s impurity potential on the energy characteristics of asymmetrical semi-exponential CsI quantum wells

Because of its unique optoelectronic properties,people have studied the characteristics of polarons in various quantum well(QW)models.Among them,the asymmetrical semiexponential QW(ASEQW)is a new model for studying the structure of QWs in recent years.It is of great significance to study the influences of the impurity and anisotropic parabolic confinement potential(APCP)on the crystal’s properties,because some of the impurities,usually regarded as Coulomb’s impurity potential(CIP),will exist in the crystal more or less,and the APCP has flexible adjustment parameters.However,the energy characteristics of the ASEQW under the combined actions of impurities and APCP have not been studied,which is the motivation of this paper.Using the linear combination operation and Lee-Low-Pines unitary transformation methods,we investigate the vibrational frequency and the ground state energy of the strong coupling polaron in an ASEQW with the influences of the CIP at the origin of coordinates and APCP,and make a comparison between our results and previous literature’s.Our numerical results about the energy properties in the ASEQW influenced by the CIP and APCP may have important significances for experimental design and device preparation.     

Oblique interaction of electrostatic nonlinear structures in relativistically degenerate dense magnetoplasmas

We have investigated the interaction of obliquely propagating ion acoustic solitary waves in a magnetoplasma with relativistically degenerate electrons. Using the quantum hydrodynamics model and by employing the extended Poincaré–Lighthill–Kuo technique, we have derived a set of Korteweg de Vries equations for two solitons. We have observed that the system under consideration allows the formation of only compressive solitons and their velocities remain in the sub-acoustic limit. Furthermore, phase shifts of solitons as a result of their interaction have been calculated. The phase shifts have been observed to be dependent on the obliqueness and the physical parameters of plasma. It has also been noticed that phase shifts remain negative for the whole range of parameters generally found in white dwarf stars. We have observed that the phase shifts enhance with the enhancement in number density, however, the converse happens when the magnetic field is enhanced. It has also been observed that the phase shift is slightly greater for the solitons that are less oblique as compared to their more oblique counterparts. Furthermore, we have estimated the spatial scales of interaction of solitons using the parameters found in white dwarf stars.     

极强激光场驱动超亮伽马辐射和正负电子对产生的研究进展

高功率超短超强激光脉冲的诞生开启了相对论非线性光学、高强场物理、新型激光聚变、实验室天体物理等前沿领域.近年来,随着数拍瓦级乃至更高峰值功率激光装置的建成,超强激光与等离子体相互作用进入到一个全新的高强场范畴.这种极强激光场与等离子体相互作用蕴含着丰富的物理过程,除了经典的波与粒子作用、相对论效应、有质动力效应等非线性物理过程外,量子电动力学(QED)效应变得格外重要,例如辐射阻尼效应、正负电子对产生、强伽马射线辐射、QED级联、真空极化等.本文主要介绍我们近年来在极端强激光场与等离子体相互作用中激发的QED效应以及伴随的超亮强伽马射线辐射和稠密正负电子对产生等方面的研究进展.