基于非简并光学参量放大器产生光学频率梳纠缠态

实验研究了阈值以下非简并光学参量放大器中的频率梳纠缠特性,在实验上制备了具有频率梳结构的Einstein-Podolsky-Rosen纠缠,实验中对5对频率梳边带间纠缠进行了测量,纠缠度约为4.5 dB.该频率梳纠缠态作为一种可扩展的量子信息系统,可为实现频分复用的多通道离物传态的实验提供必要的光源,为未来大容量的量子通信与网络提供了新思路.

Generation of continuous variable frequency comb entanglement based on nondegenerate optical parametric amplifier

Continuous variable(CV)quantum squeezed state and entangled state are important quantum resources,which have been widely used in quantum communication,quantum metrology and quantum computation.In recent years,people have paid much attention to the multi-mode optical parametric amplifier(OPO)process because the multi-mode non-classical light field is able to construct the multiplexing quantum information system for improving the working efficiency and channel capacity.As a special multi-mode optical field,optical frequency comb has been used in optical frequency measurement,atomic spectroscopy and frequency-division multiplex-based communication.Especially,there are a number of notable researches where quantum frequency combs are used,which exhibit multimode-entangled photon states.The quantum frequency combs provide a promising platform for quantum information technology based on time-bin-encoded qubits.In this paper,the entanglement characteristics of frequency comb in typeⅡnondegenerate optical parametric amplifier(NOPA)below threshold are investigated experimentally.The bipartite entanglement with frequency comb structure between idle light(ai,+n?out)and signal light(as,+n?out)is generated by the NOPA whose free spectral range(W)is1.99 GHz operated in the de-amplification state and then analyzed by dual balanced homodyne detection system(BHD)with different values of frequencyω±n?(n=0,1,2).The local light of BHD with frequencyω±n?is generated by the fiber intensity modulator and tailored by the mode cleaner.Here,we measure the correlation noise of side and frequency combs normalized to the shot noise limit relating to the phase of local oscillator beam,and we show the correlation noise of aiout and asout,the correlation noise of ai,+?out and as,-?out,the correlation noise of ai,-?out and as,+?out,the correlation noise of ai,+2?out and as,-2?out and the correlation noise of ai,-2?out and as,+2?out.The experimental results show that the five pairs of entangled states with 4.5 dB entanglement are simultaneously produced by a typeⅡOPO.Next,we can redesign NOPA to reduce its free spectral range and intracavity loss,and prepare local light with a high-order sideband frequency by fiber modulators with high bandwidth,it promises to obtain huge multiple bipartite entangled states.As a kind of extensible quantum information system,the frequency comb CV entanglement can be used to provide a necessary light source for realizing the experiment of frequency division multiplexing multi-channel teleportation,which lays a foundation for the future large-capacity quantum communication and network.