Quantum Network Based On Solid-state Single-photon Sources

Quantum networks are composed of a large number of distributed network nodes,which are connected with each other through quantum channels,and to realize the generating,sending,receiving,storing and processing of quantum states.Due to the double advantages of quantum-dot coupled with micro-cavity system in the high-performance solid-state quantum light source and spin-qubit coherent interface,it can be used as a stationary network node.The realization of high-visibility quantum interference between independent single-photons is an important element for the construction of solid-state quantum networks,which is not only the main way to establish entangled connection of network nodes,but also the important prerequisite to realize the high-fidelity quantum teleportation and entanglement swapping.This work is based on high quality solid-state quantum-dot single-photon sources,which realize the quantum interference between two independent single-photons separated by 300 km optical fiber distance.Meanwhile,we demonstrate the experimental task of boson sampling at 20-photon number,and present a medium-scale optical quantum computing.To realize the high-visibility two-photon quantum interference at a long distance is a long-pursued goal in the field of quantum networks,However,due to the limitation of quality,brightness and related experimental techniques of solid-state single-photon sources,the previous reports cannot achieve the high interference visibility and long distance at the same time.In order to simultaneously achieve these two goals,we carried out the following three aspects of work:Experimental preparation of high quality solid-state single photon Sources:We have developed two different types of micro-cavity quantum-dot systems and to prepare independent solid-state single-photon sources.And then,by measured the second-order correlation function,optical coherence properties,fine structure spectrum and other parameters of single-photon with the help of corresponding experimental set-ups,we extract the residual second-order correlation values of two independent single-photons are 0.071(1)and 0.052(1),respectively,and the Fourier-transform-limit valuesT2/2T1 are 80.8(1)%and 75.1(1)%,respectively.High-quality solid-state single photon sources are the prerequisite for realizing high-visibility quantum interference.Quantum frequency conversion:Reducing the photon transmission loss in fiber channels is an important way to improve the transmission distance of quantum networks.With the help of high-efficiency and low-noise quantum frequency conversion technologies,the wavelength of solid-state single-photon sources are converted from 890 nm in near-infrared band to 1583 nm within the telecom L-band.At the same time,we use the wavelength fine-tuning capability of quantum frequency convertor to erase the central frequency difference between the two solid-state single-photons,so as to effectively improve the degree of spectral overlap between the two wave-packets.Long-distance optical fiber transmission networks:Extending the optical fiber transmission distance between two independent single-photon sources will affect the two-photon quantum interference process mainly including the optical fiber is affected by the fluctuation of ambient temperature,which results in the time jitter for photon transmission,eventually decreasing the degree of the time domain overlap between two photon wave-packets on the interference beam-splitter;The dispersion effect of optical fiber will cause the time domain broadening of photonic wave-packets,and eventually affecting the spectral overlap of photonic wave-packets.Experimentally,we stabilize the temperature around the fiber to effectively synchronize the arrival time of two photons to the interference beam-splitter.At the same time,we use symmetrical fiber transmission architecture to eliminate the influence of fiber dispersion effect on interference visibility.Based on the above works,we carried out two-photon quantum interference experiments under the transmission distance of 24 m,101 km,201 km and 302 km respectively,and the raw interference visibility of 0.67±0.02.And then,by means of time filtering,the visibility can be futher improved to 0.93±0.04,which provides the experimental basis for the realization of high-fidelity quantum teleportation and entanglement swapping,as well as a key step for the construction of long-distance solid-state quantum networks.Demonstrating the advantage of quantum computing is another important experimental task in the field of quantum networks,the high-performance single-photon sources as an important element of linear optical quantum computing.In this paper,with the help of the high-quality solid-state quantum-dot single-photon sources,we also demonstrate the experimental task of the boson sampling with 20 photons input and 60 modes,and the spatial dimension of corresponding output states reaches 1014,which is 10 orders of magnitude higher than previous researching works.In addition,we promote the boson sampling experiment to the sparse sampling interval for the first time,and achieve the boson sampling photonic quantum computing with medium photon numbers.