The construction of quantum networks requires long-distance teleportation of multi-qubit entangled states.Here,we investigate the entanglement dynamics of GHZ and W states in fiber channels.In a fiber channel,the two ...The construction of quantum networks requires long-distance teleportation of multi-qubit entangled states.Here,we investigate the entanglement dynamics of GHZ and W states in fiber channels.In a fiber channel,the two most important phenomena that affect polarization entanglement are polarization mode dispersion(PMD)and polarization-dependent loss(PDL).We theoretically characterize how PMD and PDL vectors affect three-qubit states.In particular,upon quantifying the entanglement at the output states using concurrence and entanglement witnesses,we reveal the occurrence of entanglement sudden death and the appearance of decoherence-free subspaces in tripartite systems.Finally,we explore the evolution of GHZ and W state with an arbitrary number of photons in a fiber network and discuss the decoherence mechanism of the 4-party cluster state.展开更多
The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer st...The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer structures based photoconductive antennas are used in TDS setup as both the emitter and receiver. The experimental results demonstrate that not only the THz signal power but also the temporal waveform vary with the rotation of the exciting pulse polarization. Maximum output power of the emitter is obtained when the polarization of the pump pulse is perpendicular to the edge of the metal electrodes. At this moment the THz waveform is close to a single-cycled pulse. However, double THz pulses could be recorded when the pump laser polarization is parallel to the electrodes. Laser pulse splitting induced by the birefringence of the optical fiber may attribute to the polarizationdependent performance of the fiber-coupled THz-TDS system.展开更多
基金supported by the National Key R&D Program of China[Grant No.2017YFE0301303]。
文摘The construction of quantum networks requires long-distance teleportation of multi-qubit entangled states.Here,we investigate the entanglement dynamics of GHZ and W states in fiber channels.In a fiber channel,the two most important phenomena that affect polarization entanglement are polarization mode dispersion(PMD)and polarization-dependent loss(PDL).We theoretically characterize how PMD and PDL vectors affect three-qubit states.In particular,upon quantifying the entanglement at the output states using concurrence and entanglement witnesses,we reveal the occurrence of entanglement sudden death and the appearance of decoherence-free subspaces in tripartite systems.Finally,we explore the evolution of GHZ and W state with an arbitrary number of photons in a fiber network and discuss the decoherence mechanism of the 4-party cluster state.
基金supported by National Basic Research Program of China under Grant No.2014CB339802,No.2011CB808100National Natural Science Foundation of China under Grant No.11174156
文摘The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer structures based photoconductive antennas are used in TDS setup as both the emitter and receiver. The experimental results demonstrate that not only the THz signal power but also the temporal waveform vary with the rotation of the exciting pulse polarization. Maximum output power of the emitter is obtained when the polarization of the pump pulse is perpendicular to the edge of the metal electrodes. At this moment the THz waveform is close to a single-cycled pulse. However, double THz pulses could be recorded when the pump laser polarization is parallel to the electrodes. Laser pulse splitting induced by the birefringence of the optical fiber may attribute to the polarizationdependent performance of the fiber-coupled THz-TDS system.
