| At the end of the 19th century and the beginning of the 20th century,except for a few "dark clouds" discovered in experiments,grand underlying principles in classical physics seemed to be firmly established.However,the study of these "dark clouds"brought about a major revolution in physics.Quantum mechanics was born in the 1920s through the joint efforts of physicists.However,quantum mechanics,which describes the world in terms of wave functions,was questioned due to its conflicts with classical theory and various counterintuitive predictions.The representative one is the EPR paper published by Einstein et al.in 1935.The paper challenged the completeness of quantum mechanics by not believing in the existence of quantum randomness.Subsequently,people tried to explain the experimentally observed quantum randomness by establishing the theory of local hidden variables.Until 1964,the proposition of Bell’s theorem provided a reliable experimental test method for this protracted debate,starting a new chapter in the test of quantum theory research.In the process of Bell experiments,it was found that although the experimental results did not meet the predictions of hidden variables theory based on local realism,some extra assumptions are often need,which are called "loopholes".The realization of a "loophole-free" Bell experiment is not only of great significance for understanding and cognition of quantum theory,but also plays a decisive role in proving the existence of quantum randomness.In 1991,Ekert creatively proposed the idea of obtaining quantum randomness from the Bell experiments.The security of the quantum randomness certified and produced by the loophole-free Bell experiments could be independent of the device and only guaranteed by the results of the Bell experiments.Therefore it is called a device-independent protocol.Given some fundamental assumptions,the device-independent protocols that based on the loophole-free Bell tests guarantee the security of communication protocols.Combined with quantum communication protocols that reflect quantum advantages,such as quantum key distribution,the security of communication can be guaranteed with minimal requirements in the practical communication process.The author has participated in and carried out related works on device-independent quantum randomness and device-independent quantum key distribution.(1)Participated in the realization of device-independent quantum random number generation in 2018.The protocol mainly relies on the Entropy Accumulation Theorem(EAT)to estimate the secure randomness contained in the measurement results.For the first time in the world,the device-independent quantum random number generation against quantum adversaries was realized.(2)Responsible for the realization of device-independent quantum randomness expansion in 2021.We built a high efficiency entangled photon system in this experiment,and an upgraded version of the EAT was used,which improved the capability of the protocol to extract secure randomness.The experiment first realized that the output randomness surpasses the consumption,which promoted the application of device-independent quantum random number.(3)Responsible for the realization a proof-of-principle demonstration of device-independent quantum key distribution in 2022.The experiment further improved the efficiency on the original entangled photon system.Combined with the random post-selection,noise preprocessing and von Neumann entropy calculation method,the experiment proved the ability of our system to generate secure keys,which presented an important step toward a full demonstration of photonic device-independent quantum key distribution.(4)Besides,in 2018,the author also participated in the loophole-free Bell experiment that using cosmic photons as random sources to choose measurement settings.With the closing of detection loophole and locality loophole,a rigorous hypothesis testing of local hidden variable model was used in the experiment,which effectively proved that the experimental results did not meet the predictions of the hidden variable theory since the generation of cosmic photons(11 years ago). |
