Chinese Physics B

Wang, Xian-Jia; Chen, Wen-Man

doi: 10.1088/1674-1056/28/8/080201pmid: N/A

The emergence of cooperation still remains a fundamental conundrum in the social and behavior sciences. We introduce a new mechanism, deposit mechanism, into theoretical model to explore how this mechanism promotes cooperation in a well-mixed population. Firstly, we extend the common binary-strategy combination of cooperation and defection in public good game by adding a third strategy, namely, deposit cooperation. The players with deposit cooperation strategy pay a deposit in advance to obtain the benefits of public good at a lower contributions compared with the players with cooperation strategy, when the provision of public good is successful. Then, we explore the evolution of cooperation in the public good game with deposit by means of the replicator dynamics. Theoretical computations and stimulations show that the deposit mechanism can promote cooperation in a well-mixed population, and the numbers of equilibrium point are determined by variables of public good game. On the one hand, when the coexistence of cooperators and defectors is the stable equilibrium point in the evolutionary system, increasing the threshold of public good and adopting the weak altruism way for share benefits can enhance the level of cooperation in the population. On the other hand, if the coexistence of deposit cooperators and defectors is the stable equilibrium point, it is effective to promote the deposit cooperation by lowering the values of discount and deposit, and raising the threshold of public good.

Zhang, Lin; Liu, Junpeng

doi: 10.1088/1674-1056/28/8/080301pmid: N/A

The adiabatic control is a powerful technique for many practical applications in quantum state engineering, light-driven chemical reactions and geometrical quantum computations. This paper reveals a speed limit of nonadiabatic transition in a general time-dependent parametric quantum system that leads to an upper bound function which lays down an optimal criteria for the adiabatic controls. The upper bound function of transition rate between instantaneous eigenstates of a time-dependent system is determined by the power fluctuations of the system relative to the minimum gap between the instantaneous levels. In a parametric Hilbert space, the driving power corresponds to the quantum work done by the parametric force multiplying the parametric velocity along the parametric driving path. The general two-state time-dependent models are investigated as examples to calculate the bound functions in some general driving schemes with one and two driving parameters. The calculations show that the upper bound function provides a tighter real-time estimation of nonadiabatic transition and is closely dependent on the driving frequencies and the energy gap of the system. The deviations of the real phase from Berry phase on different closed paths are induced by the nonadiabatic transitions and can be efficiently controlled by the upper bound functions. When the upper bound is adiabatically controlled, the Berry phases of the electronic spin exhibit nonlinear step-like behaviors and it is closely related to topological structures of the complicated parametric paths on Bloch sphere.

Benzimoun, B; Daoud, M

doi: 10.1088/1674-1056/28/8/080302pmid: N/A

In this paper, we propose a new approach to tackle the separability problem for bipartite qudit mixed-states. This is based on the Majorana representation which allows to represent a N-spinors (qudit) as a symmetric state of N spin-1/2. We also discuss how we can exploit such representation and the notion of the biseparability of multipartite qubit states in the sense to establish new criteria of the separability problem based on the PPT and concurrence.

He, Shuang; Liu, Dan; Li, Ming-Hao

doi: 10.1088/1674-1056/28/8/080303pmid: N/A

We present a dissipative scheme to generate an entangled steady-state between two superconducting transmon qutrits separately embedded in two coupled transmission line resonators in a circuit quantum electrodynamics (QED) setup. In our scheme, the resonant qutrit-resonator interaction and photon hopping between resonators jointly induce asymmetric energy gaps in the dressed state subspaces. The coherent driving fields induce the specific dressed state transition and the dissipative processes lead to the gradual accumulation in the population of target state, combination of both drives the system into a steady-state entanglement. Numerical simulation shows that the maximally entangled state can be produced with high fidelity and strong robustness against the cavity decay and qutrit decay, and no requirements for accurate time control. The scheme is achievable with the current experimental technologies.

Zhang, Shu-Jing; Ma, Hong-Xin; Wang, Xiang; Zhou, Chun; Bao, Wan-Su; Zhang, Hai-Long

doi: 10.1088/1674-1056/28/8/080304pmid: N/A

Compared with the fiber channel, the atmospheric channel offers the possibility of a broader geographical coverage and more flexible transmission for continuous-variable quantum key distribution (CVQKD). However, the fluctuation of atmospheric conditions will lead to the loss of performance in atmospheric quantum communication. In this paper, we study how temperature affects atmospheric CVQKD. We mainly consider the temperature effects on the transmittance and interruption probability. From the numerical simulation analysis, it can be shown that the performance of atmospheric CVQKD is improved as temperature increases, with the other factors fixed. Moreover, the results in this work can be used to evaluate the feasibility of the experimental implementation of the atmospheric CVQKD protocols.

Li, He-Kang; Li, Ke-Min; Dong, Hang; Guo, Qiu-Jiang; Liu, Wu-Xin; Wang, Zhan; Wang, Hao-Hua; Zheng, Dong-Ning

doi: 10.1088/1674-1056/28/8/080305pmid: N/A

Realization of a flexible and tunable coupling scheme among qubits is critical for scalable quantum information processing. Here, we design and characterize a tunable coupling element based on Josephson junction, which can be adapted to an all-to-all connected circuit architecture where multiple Xmon qubits couple to a common coplanar waveguide resonator. The coupling strength is experimentally verified to be adjustable from 0 MHz to about 40 MHz, and the qubit lifetime can still be up to in the presence of the coupling element.

Zhou, Sheng-Peng; Liu, Ai-Hua; Liu, Fang; Wang, Chun-Cheng; Ding, Da-Jun

doi: 10.1088/1674-1056/28/8/083101pmid: N/A

We present a parallel numerical method of simulating the interaction of atoms with a strong laser field by solving the time-depending Schrödinger equation (TDSE) in spherical coordinates. This method is realized by combining constructing block diagonal matrices through using the real space product formula (RSPF) with splitting out diagonal sub-matrices for short iterative Lanczos (SIL) propagator. The numerical implementation of the solver guarantees efficient parallel computing for the simulation of real physical problems such as high harmonic generation (HHG) in these interaction systems.

Delibašić, Hristina; Petrović, Violeta

doi: 10.1088/1674-1056/28/8/083201pmid: N/A

The photoionization in the frame of the Ammosov–Delone–Krainov theory has been theoretically examined for noble gases, argon, krypton, and xenon, in an elliptically polarized laser field. We consider the intermediate range of the Keldysh parameter, , and analyze the influence of shifted ionization potential and temporal profile to eliminate disagreement between theoretical and experimental findings. By including these effects in the ionization rates, we solve rate equations in order to determine an expression for the ionization yield. The use of modified ionization potential shows that the ionization yields will actually decrease below the values predicted by original (uncorrected) formulas. This paper will discuss the causes of this discrepancy.

Zhao, Xiao-Yun; Wang, Chun-Cheng; Hu, Shi-Lin; Li, Wei-Dong; Chen, Jing; Hao, Xiao-Lei

doi: 10.1088/1674-1056/28/8/083202pmid: N/A

We perform a theoretical investigation on the control over the atomic excitation of Rydberg states with shaped intense ultrashort laser pulses. By numerically solving the time-dependent Schrödinger equation (TDSE), we systematically study the dependence of the population of the Rydberg states on the π phase step position in the frequency spectra of the laser pulse for different intensities, central wavelengths and pulse durations. Our results show that the Rydberg excitation process can be effectively modulated using shaped intense laser pulses with the laser intensity as high as 1×1014 W/cm2. Our work also have benefit to the future investigation to find out the dominant mechanism behind the excitation of Rydberg states in strong laser fields.

Zhou, Jun; Zhang, Jian-Shuo; Xian, Guo-Yu; Qi, Qi; Gu, Shang-Zhi; Shen, Cheng-Min; Cheng, Zhao-Hua; He, Sheng-Tai; Yang, Hai-Tao

doi: 10.1088/1674-1056/28/8/083301pmid: N/A

Metal–semiconductor Janus nanostructures with asymmetry and directionality have recently aroused significant interest, both in fundamental light–matter interactions mechanism and in technological applications. Here we report the synthesis of different Au–ZnO Janus nanostructures via a facile one-pot colloid method. The growth mechanism is revealed by a series of designed synthesis experiments. The light absorption properties are determined by both the decrease of dipole oscillations of the free electrons and the plasmon-induced hot-electron transfer. Moreover, the finite-difference time-domain (FDTD) simulation method is used to elucidate the electric field distributions of these Janus nanostructures.