Efficient infrared upconversion via a ladder-type atomic configuration

We have demonstrated experimentally that infrared light at 1529.4nm can be converted into the visible at 780nm with 54% efficiency through a ladder-type atomic configuration in 85Rb. Specifically we theoretically analyze that high efficiency is due to the large nonlinear dispersion of the index of refraction from the off-resonant enhancement in a four-wave mixing (FWM) process. By using two perpendicular polarized pump fields, the coherence of two FWM processes in this configuration is verified.Comment: The new version is published in Journal of Modern Optic

Error Analysis of Aerosol Extinction Cross Section Measurement due to Forward Scattering and Diffraction

Aerosol is a useful mean in electro-optical defence. The optical transmissivity is usually used to evaluate the performance of the aerosol. However in transmissivity measurement, forward-scattered or diffracted light might reach the detector and would be incorrectly recorded as unscattered and transmitted one, which results in the final optical density rise and experimental extinction cross-section becoming erroneously low. Based on forward scattering and diffraction analysis, the beam efficiency and effective extinction efficiency are introduced to examine the error. The results indicate that large particles and detector increase the error. To minimise the error, the distance between the aerosol and the detector must be large enough, and the detector of small area and small view angle is favourable.Defence Science Journal, 2009, 59(5), pp.545-548, DOI:http://dx.doi.org/10.14429/dsj.59.155

Variational quantum algorithms for scanning the complex spectrum of non-Hermitian systems

Solving non-Hermitian quantum many-body systems on a quantum computer by minimizing the variational energy is challenging as the energy can be complex. Here, based on energy variance, we propose a variational method for solving the non-Hermitian Hamiltonian, as zero variance can naturally determine the eigenvalues and the associated left and right eigenstates. Moreover, the energy is set as a parameter in the cost function and can be tuned to obtain the whole spectrum, where each eigenstate can be efficiently obtained using a two-step optimization scheme. Through numerical simulations, we demonstrate the algorithm for preparing the left and right eigenstates, verifying the biorthogonal relations, as well as evaluating the observables. We also investigate the impact of quantum noise on our algorithm and show that its performance can be largely improved using error mitigation techniques. Therefore, our work suggests an avenue for solving non-Hermitian quantum many-body systems with variational quantum algorithms on near-term noisy quantum computers

Measurement of Infrared Transmissivity of Smoke Using a Thermal Imager

The smoke is an effective camouflage method and is widely used in the modern battlefields.The smoke chamber test is used quantitatively to extinct the energies of the smoke material. Inthe smoke chamber test, a key problem is to accurately measure the transmissivity of the smoke.In this paper, the relationship between the temperatures measured and the radiation received bythe thermal imager has been disussed. The equation to accurately calculate the infraredtransmissivity of the smoke from the measured temperature is deduced. This equation is alsocompared with the simplified one