High coherent solid-state qubit from a pair of quantum dots

In this letter we propose a scheme to build up high coherent solid-state quantum bit (qubit) from two coupled quantum dots. Quantum information is stored in electron-hole pair state with the electron and hole locating in different dots, and universal quantum gates involving any pair of qubits are realized by effective coupling interaction via virtually exchanging cavity photons.Comment: 3 pages, 1 figur

Quantifying quantum discord and entanglement of formation via unified purifications

We propose a scheme to evaluate the amount of quantum discord and entanglement of formation for mixed states, and reveal their ordering relation via an intrinsic relationship between the two quantities distributed in different partners of the associated purification. This approach enables us to achieve analytical expressions of the two measures for a sort of quantum states, such as an arbitrary two-qubit density matrix reduced from pure three-qubit states and a class of rank-2 mixed states of 4\times 2 systems. Moreover, we apply the scheme to characterize fully the dynamical behavior of quantum correlations for the specified physical systems under decoherence.Comment: 4 pages, 2 figures, accepted for publication in Phys. Rev.

Optical Manipulation of Single Electron Spin in Doped and Undoped Quantum Dots

The optical manipulation of electron spins is of great benefit to solid-state quantum information processing. In this letter, we provide a comparative study on the ultrafast optical manipulation of single electron spin in the doped and undoped quantum dots. The study indicates that the experimental breakthrough can be preliminarily made in the undoped quantum dots, because of the relatively less demand.Comment: 3 pages, 3 figure

Number-resolved master equation approach to quantum transport under the self-consistent Born approximation

We construct a particle-number(n)-resolved master equation (ME) approach under the self-consistent Born approximation (SCBA) for quantum transport through mesoscopic systems. The formulation is essentially non-Markovian and incorporates the interlay of the multi-tunneling processes and many-body correlations. The proposed n-SCBA-ME goes completely beyond the scope of the Born-Markov master equation, being applicable to transport under small bias voltage, in non-Markovian regime and with strong Coulomb correlations. For steady state, it can recover not only the exact result of noninteracting transport under arbitrary voltages, but also the challenging nonequilibrium Kondo effect. Moreover, the n-SCBA-ME approach is efficient for the study of shot noise.We demonstrate the application by a couple of representative examples, including particularly the nonequilibrium Kondo system.Comment: arXiv admin note: substantial text overlap with arXiv:1302.638

Family Portraits: The Reconstruction of “Family Time” Through Generations

Marianne Hirsch’s concept of “liquid time” states that photographs are not fixed into static permanence but remain dynamic and unfixed as they acquire new meanings in new circumstances. I had not considered this concept until I began going through family photographs after my grandfather passed away. There I was, sitting on the sofa in my grandparents’ house, enabled by these photographs to perceive an odd thing—dining scenarios in my family photographsall represented the same behaviour of people holding cups of soft drinks, “clinking”glasses with or toasting each other, and smiling when the photographerpressed the camera shutter. No one considered this behaviour peculiar because it had already become a habit of my family’s dining culture even though my grandfather never drank soft drinks because of his diabetes. Four family photographs present dining scenarios from the 1980s to 2020. These four portraits include three print photographs and one digital photograph, and were taken at different times, by different photographers, at different locations. Within a span of forty years, these four photographs showcase a changing family performance