The Key Technologies Of Spaceborne Quantum Entanglement Source And Its Application

Quantum information is an interdisciplinary science between quantum physics and information science,which rapidly becomes one of the most hot researches in recent years.Quantum information has the advantages and prospects that classical information science cannot match,while also provide a new approach to re-understand quantum physics.Non-locality is the most controversial property of quantum physics.Since the Bell's inequality has been proposed,efforts to test the non-local correlation of quantum entanglement have never ceased.As an important step towards the ultimate test of the non-localization of quantum mechanics,a quantum entanglement source mounted on an artificial satellite can send the entangled photon pairs to two sites that are separated by more than a thousand kilometers from the ground to verify whether the quantum entangled state is still able to maintain its non-local association at large scale.I am involved in the development of the world's first spaceborne quantum entangle-ment source.The quantum entanglement source needs to withstand hostile environment such as strong vibration,high dose radiation,temperature variation,and the long-term unattended,with the weight and volume limited.For this reason,we have developed a reliable optical machine integration scheme,which combines the technologies of high precision assemble and high efficiency single-mode fiber coupling to integrate the tra-ditional parametric down-conversion quantum entanglement based on Sagnac interfer-ometer.Eventually,the integrated quantum entanglement source can produce up to 8 x 106 pairs of entangled photons per second,with fidelity over 95%.The quantum entanglement source was launched on August 16,2016 as one of the main payloads of the "Micius" quantum science experimental satellite.In-orbit test data show that the quantum entanglement source is ready to carry out the long-distance quantum en-tanglement distribution experiments between Delingha ground station and Lijiang(or Nanshan)ground station.By further improving the process of developing spaceborne quantum entanglement sources,we directly glued the fused silica material optical elements to the fused silica substrate to achieve an array of interferometers with extremely high stability and very low loss.This interferometer array can be applied to demonstrate the boson sampling.Quantum dots single photon sources have high brightness and good purity,however the interference between independent sources is still difficult.In order to obtain the identical multiphoton source,we use a pockels cell array and precisely adjusted delay fibers to rearrange a single photon pulse sequence into multiple pulse sequences.Since the repetition frequency of the current pockels cells is much lower than the repetition frequency of the single photon pulse,the pulse sequence is divided by group.Finally,we demonstrated a 5-photon/9-mode boson sampling with the sampling rate 24,000 times faster than previous studies,surpassing the first electronic computer(ENIAC)1?2 orders of magnitude.We have also applied the pockels cell array in a new quantum key distribution protocol(RRDPS-QKD),which tolerates bit error rate up to 50%.The improved bonding technology can be used to build more stable and compact optical equipment,which is a technical reserve for the quantum constellation in the future.