| Since the twentieth century,with the development of quantum mechanics theory,quantum has become more and more clear in people’s continuous exploration.In recent decades,the combination of quantum mechanics and classical optics has taken quantum optics to a world-renowned subject.More and more different kinds of quantum optical systems have emerged.And various quantum optical systems can be used for in-depth study of the principles of quantum mechanics conversely.Compared with other quantum systems,optical quantum systems are widely used because they are easier to build.In recent years,the combination of quantum mechanics and information theory has also aroused people’s interest in quantum information research.Due to the uncertainty and non-cloning of quantum states,the research on quantum information has made remarkable progress in the fields of quantum communication,quantum simulation,quantum precision measurement and quantum computing.At present,the scheme of quantum key distribution in the research of quantum information has been quite mature in theory and experimental technology,and even has developed to the commercial stage.With the further development of other quantum information researches,people are now preparing to make quantum information practical and construct practical quantum networks.The transferring of quantum states in long-distance channels is an important task for the development of quantum information networks.And optical fiber,as an important transmission channel for optical information transmission,has natural advantages for the transferring of quantum states.What‘s more,the continuous variable quantum state light field has the characteristics of certainty in preparation and no subsequent selection in detection.Therefore,the study of realizing the long-distance transferring of quantum state light field in optical fiber is particularly important for constructing unconditional continuous variable quantum communication networks.Therefore,in order to realize practical continuous variables quantum communication network,we has carried out the research on the automatic locking system,the development of low-noise photodetectors and the transferring of quantum state light field in the fiber channel.The main research contents are as follows:1.In the common quantum optics experiment,it is necessary to lock the phases of the experimental system and multiple optical fields.There are many instruments based on PDH frequency-locked technology and PLA phase-locked technology,which occupy large area,and the operation processes are tedious,and limit the scale of the experimental system and is not conducive to system integration.We design an automatic lock-in and control system based on MCU,which uses analog-to-digital conversion to identify signals,completes data analysis and calculation through MCU,and then completes signal output by digital-to-analog conversion.The automatic lock system is realized,and after the failure lock occurs,the working mode can be switched automatically to realize the re-lock.Which realizes the automatic locking of the system,and once unlocking occurs,the working mode can be automatically switched to achieve relocking.2.In the detection of non-classical light field,the required detectors are different due to the different experimental requirements.According to the actual needs of the laboratory,we designed different types of photodetectors,such as those used to detect high-frequency continuous variable quantum states,low-frequency quantum states,pulsed quantum states and weak light signals.Compared with the previous detectors,the signal-to-noise ratio,gain,bandwidth,anti-jamming and other parameters have been improved in different levels.3.In terms of the transferring of quantum state,since the loss and additional noise introduced by optical fiber increase rapidly with the length of optical fiber,and non-classical optical field is very sensitive to channel loss and additional noise,the common optical fiber transmission mode will inevitably bring additional loss to the quantum state,and even lead to the disappearance of its quantum properties.In this paper,We study the main noise sources and noise suppression methods of the fiber channel,and propose and implement a polarization and time multiplexing method for the transferring and measurement of the continuous variables non-classical state in theory and experiment,so that the transmission and measurement of the final quantum state are not affected by the fiber loss and additional noise.At the same time,we have completed the unconditional quantum teleportation experiment in the fiber channel.When the transferring distance reaches 6km,the fidelity of the restored quantum state can reach 0.62,breaking through the boundary of the classical state transferring.The innovation of this paper is as follows:1.Aiming at the complex and tedious locking system in the experimental system of quantum optics,we designed an automatic locking system to realize the automatic locking of the system.Moreover,after the locking occurs,the system can automatically switch the working mode and realize the re-locking.The experiment efficiency is improved and the experiment system is simplified.2.Various photodetectors in the experiment of quantum optics were improved,and the design conditions of various detectors in different applications were analyzed theoretically.The noise level and measurement frequency bandwidth of these detectors were significantly improved compared with those of previous detectors.3.We analyzed the influence of fiber channel noise on quantum state tansferring,and proposed a scheme to reduce the transmission noise of continuous variable quantum state,so that the squeezed state light field could still maintain non-classical characteristics after tansferring of 20 km in the fiber,and achieved 6 km deterministic quantum teleportation. |
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