Efficient entanglement purification in quantum repeaters

We present an efficient entanglement purification protocol (EPP) with controlled-not (CNOT) gates and linear optics. With the CNOT gates, our EPP can reach a higher fidelity than the conventional one. Moreover, it does not require the fidelity of the initial mixed state to satisfy F>1/2. If the initial state is not entangled, it still can be purified. With the linear optics, this protocol can get pure maximally entangled pairs with some probabilities. Meanwhile, it can be used to purify the entanglement between the atomic ensembles in distant locations. This protocol may be useful in long-distance quantum communication.     

Efficient entanglement purification in quantum repeaters

We present an efficient entanglement purification protocol(EPP) with controlled-not(CNOT) gates and linear optics.With the CNOT gates,our EPP can reach a higher fidelity than the conventional one.Moreover,it does not require the fidelity of the initial mixed state to satisfy F > 1/2.If the initial state is not entangled,it still can be purified.With the linear optics,this protocol can get pure maximally entangled pairs with some probabilities.Meanwhile,it can be used to purify the entanglement between the atomic ensembles in distant locations.This protocol may be useful in long-distance quantum communication.     

二维格气模型中动力学相变与自组织临界现象

应用数值方法研究了一种具有封闭边界条件的Manna沙堆模型——格气模型.通过模拟，发现 系统存在一个临界密度ρ_c≈0.684…，得到了相应的临界指数α≈0.452±0.02 ，并且还发现只有在特定的粒子数密度范围，系统才能体现出自组织临界性. 关键词： 沙堆模型 格气模型 自组织临界现象     

Complete Bell-state analysis for single-photon hybrid entangled state

We propose a scheme capable of performing complete Bell-state analysis for single-photon hybrid entangled state. Our single-photon state is encoded in both polarization and frequency degrees of freedom. The setup of scheme is composed of polarizing beam splitters, half wave plates, frequency shifters, and independent wavelength division multiplexers, which are feasible with current technology. We also show that, with this setup, we can perform the schemes for complete two-photon Bell-state analysis for polarization degree of freedom. Moreover, it can also be used to perform the teleportation scheme between different degrees of freedom. This setup may allow extensive applications in current quantum communications.     

Complete Bell-state analysis for a single-photon hybrid entangled state

We propose a scheme capable of performing complete Bell-state analysis for a single-photon hybrid entangled state.Our single-photon state is encoded in both polarization and frequency degrees of freedom.The setup of the scheme is composed of polarizing beam splitters,half wave plates,frequency shifters,and independent wavelength division multiplexers,which are feasible using current technology.We also show that with this setup we can perform complete two-photon Bell-state analysis schemes for polarization degrees of freedom.Moreover,it can also be used to perform the teleportation scheme between different degrees of freedom.This setup may allow extensive applications in current quantum communications.     

Electronic properties of one-dimensional systems with long-range correlated binary potentials

We study numerically the electronic properties of one-dimensional systems with long-range correlated binary potentials.The potentials are mapped from binary sequences with a power-law power spectrum over the entire frequency range,which is characterized by correlation exponent β.We find the localization length ξ increases with β.At system sizes N →∞,there are no extended states.However,there exists a transition at a threshold β c.When β > β c,we obtain ξ > 0.On the other hand,at finite system sizes,ξ≥ N may happen at certain β,which makes the system "metallic",and the upper-bound system size N (β) is given.