The research results were published online on April 12 in the international authoritative journal Nature Communications.
Quantum measurement is an indispensable means for extracting information from quantum systems. Therefore, the study of quantum measurement capabilities and limitations on the relationship between uncertainty, non-locality and other quantum physics basic problems and quantum measurement, quantum imaging, gravitational wave detection, etc. The application is of great significance.
However, due to the probability of the quantum world, in order to extract enough information, multiple identical quantum systems need to be measured. It has been found that the collective measurement of quantum can extract more than the existing individual measurement of each quantum system. Information, thus more efficient, more accurate completion of various quantum information tasks.
The so-called collective measurement refers to the simultaneous measurement of multiple identical copies of a quantum system using non-local measurements (ie, entanglement measurements). Although collective measurement has been proposed and its significance was widely recognized as early as two decades ago, it is effectively implemented. Collective measurement has always been considered as an experimentally impossible task. Therefore, most of the methods for extracting information from quantum information tasks still remain local measurements on individual quantum systems.
Li Chuanfeng and others from the University of Science and Technology of China proposed a new collective measurement method for quantum states, and achieved optimal collective measurement in experiments. This deterministic collective measurement was first used in the world for single-bit quantum state tomography. The experimental research has broken through the limits of quantum accuracy of local measurement and obtained the most efficient quantum state tomographic efficiency.
The experimental results show that the collective measurement can increase the chromatographic efficiency by at least 50%, and that the efficiency improvement range increases with the purity of the quantum state and the quantum system copy number. For example, for measuring 2048 identical copies of the general pure state, two The collective measurement efficiency of the copy is about 3 times better than the current best adaptive local measurement method.
According to reports, this research result provides a method to overcome the quantum accuracy limit of local measurement in multi-parameter quantum precision measurement, and opens up a new direction for the use of collective measurement to realize quantum information processing and basic problems in quantum mechanics research.