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[ Instrument Network Instrument Development ] Guo Guangcan, a member of the Chinese Academy of Sciences and a professor at the University of Science and Technology of China, made new progress in quantum precision measurement research. The team Li Chuanfeng, Xiang Guoyong and Yuan Haidong, professor of the Chinese University of Hong Kong, actively control non-commutative quantum channels through quantum control in the measurement of general non-commutative channel parameters. For the first time, Heisenberg precision is used to implement general non-commutable channels. Measurement of parameters. The research results were published online July 26 in the international journal Physical Review Letters.
Precision measurement is the main driver of science and technology development. Currently, the most advanced laser interference gravitational wave observatory (LIGO) in traditional precision measurement technology has reached the accuracy limit of the traditional method and is limited by the standard quantum precision limit (also called the shot noise limit). A new generation of quantum precision measurement technology can break the shot noise limit in traditional methods and reach the Heisenberg accuracy limit. At present, this kind of quantum precision measurement technology has been successfully implemented in the optical phase measurement experiment under the condition of the simplest and easy channel (the easy channel is called the easy channel when the parameters take different values). However, in the actual measurement task, the conditions of channel reconciliation are generally not satisfied, and the non-communication channel (the channel with different values ​​when the parameters are different) is ubiquitous, such as object direction measurement, quantum gyro, quantum gate tomography, etc. . However, the quantum precision measurement of non-communication channels is different from the characteristics of easy channel measurement. For example, the direct sequential measurement method of quantum precision measurement can reach the Heisenberg accuracy limit in the easy channel, but in the non-communication channel. Accuracy does not even reach the limit of shot noise accuracy in traditional methods.
In the experiment, Xiang Guoyong and others introduced the quantum control to control the non-communicating quantum channel into a pair of easy quantum channels. For the first time in the world, the Heisenberg precision limit was achieved in the measurement of general non-commutative channel parameters. However, the optimal control here generally needs adaptive update. They theoretically find the special time point that the optimal adaptation does not need to be updated, which further improves the scalability of the experiment and successfully completes eight control enhancements under the optical system. The order of measurement, the experimental accuracy tends to the Heisenberg accuracy limit. In addition, they also found an intuitive physical image of this method, revealing how the effective information in each resource in the sequential measurement is coherently accumulated, and determining the role of quantum control in regulating the coherent growth of these effective information.
Compared with the previous experimental work of measuring the precise measurement of the easy channel parameters, this work opens the way for the general channel parameter measurement to reach the Heisenberg precision limit, and also develops a new direction of using quantum control to control the quantum channel to improve the accuracy of quantum precision measurement. .
The first author of the thesis is Hou Zhibo, associate researcher of the Key Laboratory of Quantum Information of the Chinese Academy of Sciences. The authors of the paper are Xiang Guoyong and Yuan Haidong. The research was supported by the Ministry of Science and Technology, the National Natural Science Foundation of China, the Chinese Academy of Sciences and the Ministry of Education.