Wave packet transmission of Bloch electron manipulated by magnetic field

We study the phenomenon of wave packet revivals of Bloch electrons and explore how to control them by a magnetic field for quantum information transfer. It is showed that the single electron system can be modulated into a linear dispersion regime by the "quantized" flux and then an electronic wave packet with the components localized in this regime can be transferred without spreading. This feature can be utilized to perform the high-fidelity transfer of quantum information encoded in the polarization of the spin. Beyond the linear approximation, the re-localization and self-interference occur as the novel phenomena of quantum coherence.Comment: 6 pages, 5 figures, new content adde

Quantum state swapping via qubit network with Hubbard interaction

We study the quantum state transfer (QST) in a class of qubit network with on-site interaction, which is described by the generalized Hubbard model with engineered couplings. It is proved that the system of two electrons with opposite spins in this quantum network of $N$ sites can be rigorously reduced into $N$ one dimensional engineered single Bloch electron models with central potential barrier. With this observation we find that such system can perform a perfect QST, the quantum swapping between two distant electrons with opposite spins. Numerical results show such QST and the resonant-tunnelling for the optimal on-site interaction strengths.Comment: 4 pages, 3 figure

Optimization Methods for Designing Sequences with Low Autocorrelation Sidelobes

Unimodular sequences with low autocorrelations are desired in many applications, especially in the area of radar and code-division multiple access (CDMA). In this paper, we propose a new algorithm to design unimodular sequences with low integrated sidelobe level (ISL), which is a widely used measure of the goodness of a sequence's correlation property. The algorithm falls into the general framework of majorization-minimization (MM) algorithms and thus shares the monotonic property of such algorithms. In addition, the algorithm can be implemented via fast Fourier transform (FFT) operations and thus is computationally efficient. Furthermore, after some modifications the algorithm can be adapted to incorporate spectral constraints, which makes the design more flexible. Numerical experiments show that the proposed algorithms outperform existing algorithms in terms of both the quality of designed sequences and the computational complexity