Quenching across quantum critical points: role of topological patterns

We introduce a one-dimensional version of the Kitaev model consisting of spins on a two-legged ladder and characterized by Z_2 invariants on the plaquettes of the ladder. We map the model to a fermionic system and identify the topological sectors associated with different Z_2 patterns in terms of fermion occupation numbers. Within these different sectors, we investigate the effect of a linear quench across a quantum critical point. We study the dominant behavior of the system by employing a Landau-Zener-type analysis of the effective Hamiltonian in the low-energy subspace for which the effective quenching can sometimes be non-linear. We show that the quenching leads to a residual energy which scales as a power of the quenching rate, and that the power depends on the topological sectors and their symmetry properties in a non-trivial way. This behavior is consistent with the general theory of quantum quenching, but with the correlation length exponent \nu being different in different sectors.Comment: 5 pages including 2 figures; this is the published versio

Dynamics of an inhomogeneous quantum phase transition

We argue that in a second order quantum phase transition driven by an inhomogeneous quench density of quasiparticle excitations is suppressed when velocity at which a critical point propagates across a system falls below a threshold velocity equal to the Kibble-Zurek correlation length times the energy gap at freeze-out divided by $\hbar$. This general prediction is supported by an analytic solution in the quantum Ising chain. Our results suggest, in particular, that adiabatic quantum computers can be made more adiabatic when operated in an "inhomogeneous" way.Comment: 7 pages; version to appear in a special issue of New J. Phy

Probabilistic teleportation of unknown two-particle state via POVM

We propose a scheme for probabilistic teleportation of unknown two-particle state with partly entangled four-particle state via POVM. In this scheme the teleportation of unknown two-particle state can be realized with certain probability by performing two Bell state measurements, a proper POVM and a unitary transformation.Comment: 5 pages, no figur

Sowing Rate Effects on Biomass Production of a Forage Oat in the Qinghai-Tibetan Plateau

Oat (Avena sativa L.) has been a quality forage for the livestock husbandry in the Qinghai-Tibetan Plateau. But farmers tend to use high sowing rates to avoid forage production risks, which does not always give the optimum yield. An field experiment was carried out to explore the response of dry matter production of forage oat Jiayan No.2 to sowing rates in three locations of the Qinghai-Tibetan Plateau: Tianzhu county (TZ), Haiyan county (HB) and Hongyuan county (HY).The five sowing rates were set as 30 , 60 , 90 , 150 and 240 kg·ha-1. Sowing rates had a significant effect on the biomass of forage oat In TZ, the highest biomass at heading and milking stage was 14.96 t·ha-1 and 22.93 t·ha-1 under 240 and 150 kg·ha-1, respectively. In HB, 15.28 t·ha-1 and 16.75 t·ha-1 biomass yield at heading and milk stage, respectively were observed under 60 kg·ha-1. In HY, the largest biomass yield at two growth stages was up to 3.60 t·ha-1 and 7.49 t·ha-1 under 150 kg·ha-1, respectively. However, sowing rates had no significant effect on the stem/leaf biomass ratio of the plant. Based on the findings of this study, 60 and 150 kg·ha-1 had great significance on achieving high yield and it is recommended for high forage oat biomass production in the Qinghai-Tibetan Plateau

Formation of Long Single Quantum Dots in High Quality InSb Nanowires Grown by Molecular Beam Epitaxy

We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO$_2$ substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ~700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Land\'e g-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ~300 $\mu$eV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.Comment: 19 pages, 5 figure

Forage Yield of Oat on the Four Altitude Regions of the Qinghai-Tibetan Plateau

Forage oat (Avena sativa L.) for livestock in Qinghai-Tibet Plateau may be used biomass under widely different altitude conditions. To assess the effect of altitude on the biomass of oats, we conducted an experiment to explore the adaptability of forage oat Jiayan No. 2 in different altitudes for better agronomic traits and higher forage yield. Four regions included Hezheng county (2207 m a.s.l) and Tianzhu county (2407 m a.s.l), Gansu province, Haiyan county (3042 m a.s.l), Qinghai province and Hongyuan county (3460 m a.s.l), Sichuan province were selected, and agronomic data as well as dry matter yield were determined. The results showed that the phenology of heading stage was between 75-80 days after sowing in four regions. The growing degree-days (GDDs) at the heading stage decreased with the increasing of altitude. There was significant difference among Hezheng, Tianzhu, Haiyan and Hongyuan. The plant height of forage oat was 116.67 ± 2.18, 119.47 ± 1.92, 101.52 ± 3.51, and 59.04 ± 6.86 cm, respectively. The leaves area index (LAI) of oats was 3.60 ± 0.61, 4.78 ± 0.91, 6.41 ± 0.96 and 1.08 ± 0.24, respectively. The forage yield was 11.96 ± 2.98, 11.35 ± 1.58, 11.99 ± 0.84 and 2.17 ± 0.36 t·ha-1. The absolute growth rate (AGR) of biomass was 27.15 ± 6.96, 24.84 ± 3.61, 35.63 ± 3.10 and 4.94 ± 0.95 g·m-2·d-1, respectively. From perspective of forage yield and plant height, planting forage oat below 3500 m a.s.l is a preferable way to stabilize forage production in Qinghai-Tibet Plateau

Quench dynamics of topological quantum phase transition in Wen-plaquette model

We study the quench dynamics of the topological quantum phase transition in the two-dimensional transverse Wen-plaquette model, which has a phase transition from a Z2 topologically ordered to a spin-polarized state. By mapping the Wen-plaquette model onto a one-dimensional quantum Ising model, we calculate the expectation value of the plaquette operator Fi during a slowly quenching process from a topologically ordered state. A logarithmic scaling law of quench dynamics near the quantum phase transition is found, which is analogous to the well-known static critical behavior of the specific heat in the one-dimensional quantum Ising model.Comment: 8 pages, 5 figures,add new conten

Efficient electronic entanglement concentration assisted with single mobile electron

We present an efficient entanglement concentration protocol (ECP) for mobile electrons with charge detection. This protocol is quite different from other ECPs for one can obtain a maximally entangled pair from a pair of less-entangled state and a single mobile electron with a certain probability. With the help of charge detection, it can be repeated to reach a higher success probability. It also does not need to know the coefficient of the original less-entangled states. All these advantages may make this protocol useful in current distributed quantum information processing.Comment: 6pages, 3figure