ISSN 0253-2778

CN 34-1054/N

2021 Vol. 51, No. 9

Display Method:
Research Reviews
Towards long-distance quantum communication: Quantum repeaters and transportable quantum memories
ZHOU Zongquan, LI Chuanfeng
2021, 51(9): 647-653. doi: 10.52396/JUST-2021-0156
The non-cloning theorem provides the unconditional security for quantum communication but forbids the use of classical amplifiers. Therefore, the inevitable channel loss prevents the long-distance quantum communication. Protocols involving quantum memories can overcome this problem through the approach of quantum repeaters and transportable quantum memories. Based on rare-earth-ion doped crystals, we recently demonstrate an elementary link of a quantum repeater based on absorptive quantum memories and extend the optical storage time to 1 h. Here we provide a brief introduction to quantum communication, quantum repeaters and transportable quantum memories. Based on this, we review our recent achievements in this field.
Research Articles
The transmission rate of COVID-19 pandemic under different mobility control in Europe
LI Ying, SUN Tianyi, JIN Baisuo, ZHANG Bo
2021, 51(9): 654-670. doi: 10.52396/JUST-2021-0146
COVID-19 pandemic captured the full attention of the world in 2020, and the government declared a series of non-pharmacological interventions (NPIs) to curb the influence of social movement on transmission. In different countries, different policies bring about different results. Quantifying the effect of the movement becomes a vital issue for evaluating the effectiveness of these actions. The transmission rate changes and is hard to computer after altering activity. Therefore, this research sets some European countries as the research objects, collects mobility data and daily cases during some periods, and proposes a mobility-susceptible-exposure-infectious-recovery (M-SEIR) model. Unlike the SEIR model, the movement change is quantified as a variable (σ(t)) and added in the M-SEIR model. With random sampling to get the number of people in different initial states, this research iterates the model. The iterative filtering ensemble adjustment Kalman filter (IF-EAKF) is used to adjust the subsequent iterative results. In the research, it receives the changing trend of parameters and the daily new estimation in the end. Set the first round as the fitting period and repeat the experiment 100 times in the fitting part. The result confirms the feasibility and robustness of the model. In addition, this study makes a reasonable forecast for European countries about the second round. By controlling the strength and the time point of applying non-pharmacological interventions, the research predicts the impact of these actions on the pandemic and provides some suggestions for the deployment of relevant policies in the future. Finally the study eliminates the external factors such as motion and temperature, and obtains an interesting discovery: Despite the daily case in the third round higher than that in the first round, the transmission parameter in the former appears lower than that in the latter. The further survey shows that it might be related to vaccination.
Financing the overconfident newsvendor under the information asymmetry
YANG Feng, CHANG Yuxin, BI Chen
2021, 51(9): 671-689. doi: 10.52396/JUST-2021-0105
Overconfident newsvendors perceive the expected outcome of an uncertain event as more certain than actuality.Built upon the classic newsvendor model, a system with a profit-maximizing bank and an overconfident retailer is studied, where the retailer is capital-constrained and might borrow bank loans. Based on retailers’ initial capital, we clarify them as severely poor, medium poor and rich, respectively. We obtain the equilibrium order quantity and bank interest rate under the information symmetry and asymmetry. Under the information symmetry, when the retailer is severely poor or medium poor, he always accesses bank loans. Under the information asymmetry, when the retailer is severely poor, he borrows from the bank. However, when the retailer is medium poor, he uses up all his initial capital without borrowing bank loans. The retailer with limited funds is willing to disclose his cognition of the market demand to the bank. The information asymmetry might reduce the loss of the system’s profit, which is caused by double marginalization effect.
Production planning in a multi-product manufacturing system considering the carbon cap and trade mechanism and product recycling mechanism
GUI Liqin, LI Jun, HU Donglan, HONG Jing, WANG Shanyong
2021, 51(9): 690-698. doi: 10.52396/JUST-2021-0175
With the deterioration of ecological environment and the shortage of natural resources, firms are forced to change and adjust their production planning along an environmentally friendly road to reduce the negative effects on the environment. This paper investigate the optimal production planning in a multi-product manufacturing system considering the product recycling mechanism and carbon cap and trade mechanism, in which a firm uses limited machine capacity, working time and carbon quotas to manufacture multiple products for fulfilling stochastic market demands. Based on the cost-volume-profit analysis, a profit maximization model is proposed to characterize the optimization problem. In this model, the cost structure consists of production cost, holding or shortage cost, recycling cost and carbon cost. The revenue structure consists of sales revenue and recycling benefits.According to the profit maximization model and the numerical example, the optimal production and recycling decisions are analyzed. Meanwhile, the effects of cap and trade mechanism and product recycling mechanism on production quantity, total carbon emissions and total profits are also investigated. The results indicate that under the carbon cap and trade mechanism and the product recycling mechanism, a higher carbon permit price can motivate manufacturers to produce green product, and that product recycling mechanism is beneficial to lower carbon emissions and increase the firm profit. Managerial insights and suggestions for future research are given.
The effect of the Shanghai-Hong Kong Stock Connect program on market efficiency in China
WANG Yuchen, CAI Jingwei
2021, 51(9): 699-716. doi: 10.52396/JUST-2021-0157
We study the effect of the Shanghai-Hong Kong Stock Connect program on market efficiency in China. Applying a difference-in-differences model, we find that connected firms experience a higher about 4% price impact and significantly increased turnover, liquidity, and volatility in 20 days following the announcement. Our results support the evidence that investors demand a premium for volatility risk. Furthermore, in the Shanghai market, the participation of Hong Kong investors helps reduce the volatility of connected stocks, while in the Hong Kong market, the participation of Shanghai investors increases the volatility. The finding of this cross-market variation is consistent with the heterogeneity of investors’ trading behavior across different markets and reflects the existence of risk spillovers between those two markets. The price revaluation and risk spillovers illustrate that the implementation of the program has greatly improved the efficiency of the Chinese market.