Entanglement and discord assisted entropic uncertainty relations under decoherence

The uncertainty principle is a crucial aspect of quantum mechanics.It has been shown that quantum entanglement as well as more general notions of correlations,such as quantum discord,can relax or tighten the entropic uncertainty relation in the presence of an ancillary system.We explored the behaviour of entropic uncertainty relations for system of two qubits—one of which subjects to several forms of independent quantum noise,in both Markovian and non-Markovian regimes.The uncertainties and their lower bounds,identified by the entropic uncertainty relations,increase under independent local unital Markovian noisy channels,but they may decrease under non-unital channels.The behaviour of the uncertainties(and lower bounds)exhibit periodical oscillations due to correlation dynamics under independent non-Markovian reservoirs.In addition,we compare different entropic uncertainty relations in several special cases and find that discord-tightened entropic uncertainty relations offer in general a better estimate of the uncertainties in play.     

Uncertainty relation of successive measurements based on Wigner–Yanase skew information

Wigner-Yanase skew information could quantify the quantum uncertainty of the observables that are not commuting with a conserved quantity.We present the uncertainty principle for two successive projective measurements in terms of Wigner-Yanase skew information based on a single quantum system.It could capture the incompatibility of the observables,i.e.the lower bound can be nontrivial for the observables that are incompatible with the state of the quanaim system.Furthermore,the lower bound is also constrained by the quantum Fisher information.In addition,we find the complementarity relation between the uncertainties of the observable which operated on the quantum state and the other observable that performed on the post-measured quantum state and the uncertainties formed by the non-degenerate quantum observables performed on the quantum state,respectively.     

Quantum uncertainty relations of Tsallis relative α entropy coherence based on MUBs

In this paper,we discuss quantum uncertainty relations of Tsallis relative α entropy coherence for a single qubit system based on three mutually unbiased bases.For α∈[1/2,1)U(1,2],the upper and lower bounds of sums of coherence are obtained.However,the above results cannot be verified directly for any α∈(0,1/2).Hence,we only consider the special case of α=1/n+1,where n is a positive integer,and we obtain the upper and lower bounds.By comparing the upper and lower bounds,we find that the upper bound is equal to the lower bound for the special α=1/2,and the differences between the upper and the lower bounds will increase as α increases.Furthermore,we discuss the tendency of the sum of coherence,and find that it has the same tendency with respect to the different θ or φ,which is opposite to the uncertainty relations based on the Rényi entropy and Tsallis entropy.     

Dynamics of entropic uncertainty for three types of three-level atomic systems under the random telegraph noise

We study the dynamics of the entropic uncertainty for three types of three-level atomic systems coupled to an environment modeled by random matrices. The results show that the entropic uncertainty in the Ξ-type atomic system is lower than that in the V-type atomic system which is exactly the same as that in the Λ-type atomic system. In addition, the effect of relative coupling strength on entropic uncertainty is opposite in Markov region and non-Markov region, and the influence of a common environment and independent environments in Markov region and non-Markov region is also opposite. One can reduce the entropic uncertainty by decreasing relative coupling strength or placing the system in two separate environments in the Markov case. In the non-Markov case, the entropic uncertainty can be reduced by increasing the relative coupling strength or by placing the system in a common environment.     

Uniaxial stress influence on lattice, band gap and optical properties of n-type ZnO： first-principles calculations

The lattice,the band gap and the optical properties of n-type ZnO under uniaxial stress are investigated by firstprinciples calculations.The results show that the lattice constants change linearly with stress.Band gaps are broadened linearly as the uniaxial compressive stress increases.The change of band gap for n-type ZnO comes mainly from the contribution of stress in the c-axis direction,and the reason for band gap of n-type ZnO changing with stress is also explained.The calculated results of optical properties reveal that the imaginary part of the dielectric function decreases with the increase of uniaxial compressive stress at low energy.However,when the energy is higher than 4.0 eV,the imaginary part of the dielectric function increases with the increase of stress and a blueshift appears.There are two peaks in the absorption spectrum in an energy range of 4.0-13.0 eV.The stress coefficient of the band gap of n-type ZnO is larger than that of pure ZnO,which supplies the theoretical reference value for the modulation of the band gap of doped ZnO.     

Influence of homodyne-based feedback control on the entropic uncertainty in open quantum system

For an open quantum system containing two qubits under homodyne-based feedback control, we investigate the dynamical behaviors of quantum-memory-assisted entropic uncertainty.Moreover, we analyze the influence of feedback modes and coefficients on the entropic uncertainty.Numerical investigations show that the memory qubit should be placed in a non-dissipative channel if the single dissipative channel condition can be chosen, which helps reduce the entropic uncertainty of the system.For the homodyne feedback control F = λσ_x(or F = λσ_y), due to different roles of the entangled qubits A and B, when they are subject to feedback control with different feedback coefficients λ, the exchange of feedback coefficients will cause variations of the entropic uncertainty.When the feedback coefficient corresponding to the memory qubit B is larger(λ_B λ_A), the steady value of the entropic uncertainty will be small, which is conducive to enhancing the robustness of the system.However, for the feedback control F = λσ_z, the difference between the feedback coefficients has no effect on the steady values of the entropic uncertainty.     

Complementary relation between quantum entanglement and entropic uncertainty

Quantum entanglement is regarded as one of the core concepts,which is used to describe the nonclassical correlation between subsystems,and entropic uncertainty relation plays a vital role in quantum precision measurement.It is well known that entanglement of formation can be expressed by von Neumann entropy of subsystems for arbitrary pure states.An interesting question is naturally raised:is there any intrinsic correlation between the entropic uncertainty relation and quantum entanglement?Or if the relation can be applied to estimate the entanglement.In this work,we focus on exploring the complementary relation between quantum entanglement and the entropic uncertainty relation.The results show that there exists an inequality relation between both of them for an arbitrary two-qubit system,and specifically the larger uncertainty will induce the weaker entanglement of the probed system,and vice versa.Besides,we use randomly generated states as illustrations to verify our results.Therefore,we claim that our observations might offer and support the validity of using the entropy uncertainty relation to estimate quantum entanglement.     

Influence of the Choice of NN Potential Model on γd→τ~0d Observables near η-Threshold

Influence of the choice of the NN potential model governing the deuteron wave function on the observables for coherent i~0-photoproduction on the deuteron near η-threshold is investigated by using a three-body model for the intermediate ηNN system with separable two-body interactions.Results for unpolarized differential cross section and polarization observables are predicted.It is revealed that the choice of the NN potential model has a visible effect on the differential cross section and most of the polarization observables,especially in the photon energy range of 600-800 MeV and extreme backward pion angles.We find that the deviation among results obtained by using different deuteron wave functions is quite large.The use of the CD-Bonn NN potential for deuteron wave function doubles the differential cross section in this kinematic region.Compared with the experimental data from CLAS collaboration for differential cross section,sizeable discrepancies are found.     

Generation of new longitudinal modes in an amplifying dye solution

A novel phenomenon is reported for the first time that the generation of the newlongitudinal modes in amplifying multi-longitudinal mode laser in a dye amplifier.The newmodes are located on the violet side within the gain band of the amplifing medium.The phe-nomenon is explained by the theory of third-order nonlinear polarization in the case of four-wave resonances.The intensity of the new modes created are comparable with or even higherthan that of the original modes.The effect can be expected to serve as a new method for ex-tention of spectral tuning ranges of laser.     

FM-PERCEPTION THRESHOLD OF NARROW BAND NOISE

A narrow band noise sounds with a definite pitch,the highness depending on its central frequency(f)and the tonality or"brightness"on its bandwidth(B).Among normal subjects,for a given f,theperception threshold of frequency modulation(△f)is found to be a function of B and can be expressedas △f=AB~n,where A is a calculated value of △f with B equaling 1 Hz,quite close to pure tone △f.Value n varies within a range of 0.22—0.45 for f below 4000 Hz,being somewhat smaller for 4000 and8000 Hz.The △f-versus-fcorrelation curve of narrow band noise is quite similar to that of pure tones,provided △f values are taken with the same B/f ratio.Intensity of the carrier(20—80 dB)exerts very littleeffect on △f.△f of narrow band noise also varies in inverse proportion to the square root of mod-ulation duration(up to 172 ms),as does FM-perception threshold of pure tone.     

A Lower Bound on Concurrence

We derive an analytical lower bound on the concurrence for bipartite quantum systems with an improved computable cross norm or realignment criterion and an improved positive partial transpose criterion respectively. Furthermore we demonstrate that our bound is better than that obtained from the local uncertainty relations criterion with optimal local orthogonal observables which is known as one of the best estimations of concurrence.     

Electromagnetic field quantization and input–output relation for anisotropic magnetodielectric metamaterial

A phenomenological quantization of electromagnetic field is introduced in the presence of the anisotropic magnetodielectric metamaterial.For a single layer structure with the anisotropic metamaterial,input–output relations of quantized radiation are derived using the Green-function approach.Based on these relations,the reflectance of the linearly polarized wave through this structure is calculated.The results show that different resonant peaks of reflectance appear for different polarized waves and indicate the use of the anisotropic metamaterial as a reflector for a certain polarized wave.Furthermore it is found that such a structure can realize the resonant gap with the increase of the thickness.Finally the effects of the absorption are considered and we find that the above properties do not change with the introduction of the absorption.     

Effects of Electric Field on Electronic States in a GaAs/GaAlAs Quantum Dot with Different Confinements

Binding energies of shallow hydrogenic impurity in a GaAs/GaAlAs quantum dot with spherical confinement, parabolic confinement and rectangular confinement are calculated as a function of dot radius in the influence of electric field. The binding energy is calculated following a variational procedure within the effective mass approximation along with the spatial depended dielectric function. A finite confining potential well with depth is determined by the discontinuity of the band gap in the quantum dot and the cladding. It is found that the contribution of spatially dependent screening effects are small for a donor impurity and it is concluded that the rectangulax confinement is better than the parabolic and spherical confinements. These results are compared with the existing literature.     

Effects of ⅢB transition metals on optoelectronic and magnetic properties of HoMnO_3: A first principles study

The optoelectronic and magnetic properties of pure Ho Mn O3 and Ho0.67T0.33 Mn O3(T = La, Y) alloys in hexagonal phase are theoretically investigated by using the first-principles calculations. The investigations are performed by means of the density functional theory through using the spin polarized generalized gradient approximation plus the Hubbard potential(SPGGA + U, U eff= 3 eV). The studied material Ho MnO3 exhibits two indirect band gaps: 1.58 eV for the spinup state and 0.72 eV for the spin-down state along the S–G direction within the SPGGA + U approximation. It is found that the band gap of pure Ho Mn O3 for the spin-up state increases with increasing La and Y dopants. The results show that all of the studied materials have semi-metallic behaviors for the spin-up state and semiconducting character for the spin-down state. The substitutions of La and Y for Ho in Ho MnO3 cause the static dielectric constant(ε0) to increase in the x direction but to decrease in the z direction. The calculated optical conductivity spectrum of Ho MnO3 in a low energy range is in good agreement with the recent experimental data.     

Controlling the entropic uncertainty and quantum discord in two two-level systems by an ancilla in dissipative environments

The uncertainty principle is a crucial aspect of quantum mechanics.It has been shown that the uncertainty principle can be tightened by quantum discord and classical correlation in the presence of quantum memory.We investigate the control of the entropic uncertainty and quantum discord in two two-level systems by an ancilla in dissipative environment.Our results show that the entropic uncertainty of an observed system can be reduced and the quantum discord between the observed system and the quantum memory system can be enhanced in the steady state of the system by adding an dissipative ancilla.Particularly,via preparing the state of the system to the highest excited state with hight fidelity,the entropic uncertainty can be reduced markedly and the quantum discord can be enhanced obviously.We explain these results using the definition of state fidelity.Furthermore,we present an effective strategy to further reduce the the entropic uncertainty and to enhance the the quantum discord via quantum-jump-based feedback control.Therefore,our results may be of importance in the context of quantum information technologies.     

Behaviors of harmonic signals in wavelength-modulated spectroscopy under high absorption strength

Behaviors of harmonic signals in wavelength modulation spectroscopy(WMS)for gas detection with Lorentzian line under high absorption strength are investigated.Approximate analytic expressions of the second,fourth,and sixth harmonics on the strength are presented in concise forms.Simulations show that the expressions are in agreement with the Fourier expansion by numerical integration.It is expected theoretically and experimentally in a WMS system for methane detection that there are not only a maximum,but also a null point in the harmonics versus strength relations,which should be of practical importance in methane sensing applications.     

Measurement of the Floor Tilt in Experimental Determination of the Gravitational Constant

A prototype of a device with an impact structure for measuring the floor tilt has been built in our laboratory. The mechanical construction and the capacitive transducer of the device are introduced. Experimental results indicate that the floor tilt is about 16#tad in our cavity laboratory, and the uncertainty AG/G caused by such tilt is less than 0.54 parts per million (ppm), so the floor tilt can be reasonably neglected in the experimental determination of the gravitational constant G with the total uncertainty of about l0ppm.     

Unconventional phonon spectra and obstructed edge phonon modes

Based on the elementary band representations(EBR), many topologically trivial materials are classified as unconventional ones(obstructed atomic limit), where the EBR decomposition for a set of electronic states is not consistent with atomic valenceelectron band representations. In the work, we identify that the unconventional nature can also exist in phonon spectra, where the EBR decomposition for a set of well-separated phonon modes is not consistent with atomic vibration band representations(A...     

First-principles investigations of electronic structures and optical properties in wurtzite Zn16O13N2F and Zn14O15Ag2F

Generally,Ag and N can be taken as relatively better candidates for p-type ZnO.In this letter,we investigate the electronic structures and optical properties of N-or Ag-doped ZnO with F as the reactive donor.F atom is found to not only enhance acceptor solubilities,but also lower acceptor levels in the band gap of co-doped ZnO.In addition,we analyze the imaginary portion of the dielectric functions,refractive indices,and loss functions for pure and co-doped ZnO.A comparison with pure ZnO shows that the remarkable feature for these co-doped ZnO is a strong absorption in the visible light region,indicating that they could be taken as the potential candidates for photocatalytic material.     

Effect of Connected Multi-Ring Impurity Scattering on Quantum Transport

We investigate the quantum transmission properties of connected multi-rings with impurities and analyse the effect of the impurities on the band formation in these geometric structures. It is shown that energy bands and band gaps are formed clearly while there is not any fixed band structure for the case of the single ring. The number of resonant peaks in conductance bands increases with the number of rings. Some essential differences are pointed out and magnetic properties of loop configurations in the presence of Aharonov-Bohm flux are explored as well.