Capacity of a simultaneous quantum secure direct communication scheme between the central party and other M parties

We analyze the capacity of a simultaneous quantum secure direct communication scheme between the central party and other $M$ parties via $M+1$-particle GHZ states and swapping quantum entanglement. It is shown that the encoding scheme should be secret if other $M$ parties wants to transmit $M+1$ bit classical messages to the center party secretly. However when the encoding scheme is announced publicly, we prove that the capacity of the scheme in transmitting the secret messages is 2 bits, no matter how big $M$ is.Comment: 3 page

Electron-phonon coupling and superconductivity in LiB1+x_{1+x}C1−x_{1-x}

By means of the first-principles density-functional theory calculation and Wannier interpolation, electron-phonon coupling and superconductivity are systematically explored for boron-doped LiBC (i.e. LiB$_{1+x}$C$_{1-x}$), with $x$ between 0.1 and 0.9. Hole doping introduced by boron atoms is treated through virtual-crystal approximation. For the investigated doping concentrations, our calculations show the optimal doping concentration corresponds to 0.8. By solving the anisotropic Eliashberg equations, we find that LiB$_{1.8}$C$_{0.2}$ is a two-gap superconductor, whose superconducting transition temperature, T$_c$, may exceed the experimentally observed value of MgB$_2$. Similar to MgB$_2$, the two-dimensional bond-stretching $E_{2g}$ phonon modes along $\Gamma$-$A$ line have the largest contribution to electron-phonon coupling. More importantly, we find that the first two acoustic phonon modes $B_1$ and $A_1$ around the midpoint of $K$-$\Gamma$ line play a vital role for the rise of T$_c$ in LiB$_{1.8}$C$_{0.2}$. The origin of strong couplings in $B_1$ and $A_1$ modes can be attributed to enhanced electron-phonon coupling matrix elements and softened phonons. It is revealed that all these phonon modes couple strongly with $\sigma$-bonding electronic states.Comment: 7 pages, 10 figures, accepted for publication in EP

IMPROVING THE REGULATIVE ENVIRONMENT TO FACILITATE THE EXPLOITATION OF INFORMATION RESOURCES IN THE PEOPLE’S REPUBLIC OF CHINA

A supportive regulatory environment is necessary to facilitate the development and utilisation of information resources in China. The legal system and its enabling policies for information resources should focus on removing all the macro-level obstacles in order to promote and ensure the positive feedback effect of information cycles. This would include constructing a competitive market, enhancing infrastructure, strengthening taxation and financing the supporting system. The core interest in information exploitation is intellectual property (IP). There are five levels of IP protection: judicial trial, administrative execution, technological measures, collective management and industry discipline as well as private control. While strengthening IP protection ranks as the Government’s priority policy, the free distribution and sharing of information should be strongly advocated to optimise the development and utilisation of information resources. Digital information is playing a more significant role in our society than physical goods in regard to quantity and effects. Digital information is changing the whole world, with for instance, E-government, Ecommerce and E-life. Information resources have become an important asset and key driver for social development. The ‘Developmental Strategy for Informatisation in China 2006-2020’ issued by the Communist Party of China (CPC) Central Committee and the State Council declares that informatisation is a key strategy for maintaining national competitiveness and sustainability. 1 The key of informatisation is the development and utilization of information resources. While this is rather weak in China, enhancing the development and utilisation of information resources has been ranked as a priority government task because of the value in constructing a flexible and enabling regulatory framework