Quantum coherence is the most distinct feature of quantum mechanics.However,inevitable decoherence processes will finally destroy it and make the"Schrödinger's cat"invisible in our classical world.I...Quantum coherence is the most distinct feature of quantum mechanics.However,inevitable decoherence processes will finally destroy it and make the"Schrödinger's cat"invisible in our classical world.In this"quantum-to-classical transition",the so-called"largeness"plays a critical role.We experimentally study the largeness phenomena in the bipartite entanglement decay process through a depolarizing channel with two-photon entangled states generated from a spontaneous parametric down-conversion source.Our experiment demonstrates how the speed of entanglement decay and the time when"entanglement sudden death"happens depend on the size of the system exposed to the environment noise.展开更多
We present a theoretical and experimental study on the bandwidth of parametric down-converted photons generated from periodically poled lithium niobate(PPLN)crystal pumped by a pulsed laser.By comparison of crystals w...We present a theoretical and experimental study on the bandwidth of parametric down-converted photons generated from periodically poled lithium niobate(PPLN)crystal pumped by a pulsed laser.By comparison of crystals with different lengths and pump beams of different bandwidths,we demonstrate that the bandwidth of down-converted photons will increase for a broader bandwidth of pump pulse and decrease for a longer crystal,but the influence of crystal length will become weaker along with increase of both crystal length and pump pulse bandwidth.Especially under the conditions of our experiment,the bandwidth almost remains unchanged for longer crystals when pumped by a femtosecond laser.This may be helpful for schemes in which pulsed lasers are used to pump PPLN crystals.展开更多
基金by the National Basic Research Program of China under Grant No 2011CB921200the National Natural Science Foundation of China under Grant Nos 11074242 and 10874162+3 种基金the Knowledge Innovation Project of Chinese Academy of Sciencesthe Program for New Century Excellent Talents in Universitythe International Cooperation Program from CAS and the Ministry of Science and Technology of Chinathe Foundation for the Author of National Excellent Doctoral Dissertation of of China under Grant No 200729.
文摘Quantum coherence is the most distinct feature of quantum mechanics.However,inevitable decoherence processes will finally destroy it and make the"Schrödinger's cat"invisible in our classical world.In this"quantum-to-classical transition",the so-called"largeness"plays a critical role.We experimentally study the largeness phenomena in the bipartite entanglement decay process through a depolarizing channel with two-photon entangled states generated from a spontaneous parametric down-conversion source.Our experiment demonstrates how the speed of entanglement decay and the time when"entanglement sudden death"happens depend on the size of the system exposed to the environment noise.
基金by the National Basic Research Program of China under Grant No 2006CB921907the National Natural Science Foundation of China under Grant No 10774139+3 种基金the Innovation Funds from Chinese Academy of Sciencesthe Program for New Century Excellent Talents in Universitythe Foundation for Author of National Excellent Doctoral Dissertation of China under Grant No 200729the Fundamental Research Funds for the Central Universities.
文摘We present a theoretical and experimental study on the bandwidth of parametric down-converted photons generated from periodically poled lithium niobate(PPLN)crystal pumped by a pulsed laser.By comparison of crystals with different lengths and pump beams of different bandwidths,we demonstrate that the bandwidth of down-converted photons will increase for a broader bandwidth of pump pulse and decrease for a longer crystal,but the influence of crystal length will become weaker along with increase of both crystal length and pump pulse bandwidth.Especially under the conditions of our experiment,the bandwidth almost remains unchanged for longer crystals when pumped by a femtosecond laser.This may be helpful for schemes in which pulsed lasers are used to pump PPLN crystals.
