Quantum transmission through the n-p-n heterojunction of massive 8-Pmmn borophene

We investigate the quantum transmission through the n-p-n heterojunction of massive 8-Pmmn borophene. It is found that the Dirac mass of the electron interacts with the anisotropy of the 8-Pmmn borophene, leading to the occurrence of new transmission behaviors in this n-p-n heterojunction. Firstly, the effective energy range of nonzero transmission can be reduced but deviates from the mass amplitude, which induces the further controllability of the transmission property. Secondly, even if the equal-energy surfaces in the p and n parts do not encounter in the k-space, finite transmission is allowed to occur as well. In addition, the existence of Dirac mass can change the reflection manner from the retroreflection to the specular reflection under appropriate conditions.

Entropic singularities give rise to quantum transmission

When can noiseless quantum information be sent across noisy quantum devices? And at what maximum rate? These questions lie at the heart of quantum technology, but remain unanswered because of non-additivity— a fundamental synergy which allows quantum devices (aka quantum channels) to send more information than expected. Previously, non-additivity was known to occur in very noisy channels with coherent information much smaller than that of a perfect channel; but, our work shows non-additivity in a simple low-noise channel. Our results extend even further. We prove a general theorem concerning positivity of a channel’s coherent information. A corollary of this theorem gives a simple dimensional test for a channel’s capacity. Applying this corollary solves an open problem by characterizing all qubit channels whose complement has non-zero capacity. Another application shows a wide class of zero quantum capacity qubit channels can assist an incomplete erasure channel in sending quantum information. These results arise from introducing and linking logarithmic singularities in the von-Neumann entropy with quantum transmission: changes in entropy caused by this singularity are a mechanism responsible for both positivity and non-additivity of the coherent information. Analysis of such singularities may be useful in other physics problems.

Quantum wireless network communication based on cluster states

Due to the high security of quantum transmission and the more flexible and economical implementation of wireless communication, quantum wireless network communication attracts lots of attention. Because of the high entanglement persistence and robustness of cluster states against decoherence and loss, we investigate the application of cluster states in quantum wireless network communication (QWNC) and propose several kinds of QWNC schemes based on 1D, 2D and 3D cluster states, respectively. Finally we propose a QWNC scheme under the bilayer quantum network architecture. Comparing with other multi-hop teleportation schemes, it is unnecessary for the intermediate nodes to perform entanglement swapping to establish the required entanglement. The computational complexity is independent of the number of intermediate nodes and cluster states are allocated on demand, thus reducing the computational complexity and resource consumption largely.

New quantum key agreement protocol with five-qubit Brown states

We propose a new two-party quantum key agreement (QKA) protocol using five-qubit Brown states. One-way quantum transmission can be realized by merging Brown states and decoy photons randomly. The security of this protocol is shown to resist the outsider attack and participant attack over the ideal channel. Some methods are also proposed to ensure its security in noisy and lossy quantum channel. Finally, we generalize it and propose a multi-party QKA protocol based on Brown states.

Electronic transport through renormalized DNA chains

DNA have presented through experiments great variability in terms of its electronic characteristics. They have shown that it can acquire the behavior of a conductor, semiconductor or insulator, making it a good candidate for replicating at the mesoscopic scale electronic devices. In the present work, the quantum transmission coefficient is calculated for DNA chains of various lengths with the use of the decimation and renormalization procedure, within the tight binding approximation and the Lippmann-Schwinger scattering theory. Transmission-Energy profiles were obtained, which helped to infer electronic transport properties of the system, Additionally, the current-voltage relation for a 30-pairs chain was calculated as well, and compared with the experimental results of Porath et al. Results show the semiconductor characteristics of the molecule, and a resemblance with the work of Porath, showing the quality of the procedure and the model utilized.

The quantum transmission characteristic of one-dimensional photonic crystals

In this paper, we have given the quantum transfer matrix, quantum dispersion relation, quantum transmissivity and reflectivity of one-dimensional photonic crystals with the quantum theory of photon. We have studied the quantum transmission characteristic of different structure one-dimensional photonic crystals, which include mirror and nonmirror structures, with and without defect, and the defects are active and inactive media. On that basis, we compared the dispersion relation, transmissivity and reflectivity of quantum with classical for one-dimensional photonic crystals, and found they are identical, which indicate the quantum theory approach of photonic crystals is true, it can further study the quantum topological property of photonic crystals, such as quantum Zak phase, Chern number and quantum edge state and so on.