Research On The Loophole-free Bell Inequality Test And Device-independent Quantum Random Numbers

Quantum mechanics has been accompanied by doubts and debates since its birth.A group of scientists represented by Einstein firmly believed in local realism.They insisted that quantum mechanics was only an incomplete description of the objective world,while the other party represented by Bohr believed that quantum mechanics was the real description of the objective world.These two sides began a debate for nearly three decades,until John Bell proposed the famous Bell inequality in 1964,making this protracted debate the first time to be verified by experimental means.Bell’s theory pointed out that some predictions of quantum mechanics cannot be understood by local realism.The violation of Bell’s inequality embodies this conflict between quantum mechanics and local realism.In the previous Bell’s inequality ex-periments,the experimental results all support the description of quantum mechanics to the objective world,but due to the difference between the actual experiment and the ideal model,different assumptions have to be introduced to ensure the validity of the experimental results.These assumptions will open some loopholes,which may allow the local realism to explain the phenomenon in those experiment.Therefore,to further verify the completeness of quantum mechanics,it is particularly important to imple-ment the loophole-free Bell test.One of the main work introduced in this paper is that we closed the local loopholes and the detection efficiency loopholes at the same time,using the randomness from the cosmic source to choose the measurement basis,so as to exclude the local hidden variables for the first time within 11 years before the start of the experiment,which verifies the establishment of quantum nonlocality.Another work is that on the basis of the loophole-free Bell test,we have also im-plemented the device-independent quantum randomness expansion for the first time.Without trusting the internal working state of the system device,we extend the shorter random sequence to a longer random sequence,thereby achieving a net increase in ran-domness.During the entire experiment,we spent 12.5 hours,consumed 4.39×108 bits of randomness,and produced 5.47 × 108 bits of randomness,and finally realized 1.08 × 108 bits of random expansion.According to quantum probability estimation theory,our experiment can provid the highest security level of randomness resources against quantum attacks,which not only deepens our understanding of randomness,but also lays a solid foundation for bringing device-independent quantum random numbers into practical application scenarios.