The strongest quantum intertextuality in monolithic quantum systems has been observed

The team of Academician Guo Guangcan of the University of Science and Technology of China has made important progress in the research of basic problems in quantum physics. The team collaborated with Professor Chen Jingling of Nankai University and Professor Adán Cabello of the University of Seville in Spain to experimentally study the quantum association corresponding to the non-locality of many-body in a single high-dimensional quantum system, so as to observe the strongest quantum intertextuality in a single quantum system so far. On June 13, the relevant research results were published in Physical Review Letters.

Schematic diagram of intertextuality extracted from three-body non-locality. Photo courtesy of China University of Science and Technology

Quantum intertextuality is a peculiar property of quantum mechanics and an important resource for achieving universal quantum computing. It refers to the fact that the result of a physical quantity under a quantum measurement depends on the way the measurement is made, not just the quantity being measured. Quantum intertextuality makes quantum mechanics incompatible with any theory of hidden variables that are non-intertextual, and quantum intertextuality is closely related to quantum non-locality. Quantum nonlocality is the manifestation of quantum intertextuality contradicting the theory of non-intertextual hidden variables in many-body systems. The violation value of Bell’s inequality can characterize the magnitude of nonlocality, and studies have shown that the violation value of Bell’s inequality can increase exponentially with the number of qubits. However, although richer measurements can be constructed in monolithic high-dimensional quantum systems than in many-body systems, how to obtain intertextuality beyond the strength of non-localized associations in them has been an open question.

In order to construct and observe stronger quantum intertextuality associations in monomeric systems, the research group started from the graph theory method of quantum associations, abstracted the reciprocity relationship between the measurements used in the non-localized association into a class of graphs, and looked for another set of measurements in the monolithic high-dimensional system that was isomorphic to the graph, so as to completely quantify the non-classical characteristics of the quantum association with the parameters of the graph. The research team found that when the Mermin-Ardehali-Belinskii-Klyshko (MABK) Bell inequality, which is non-classical with exponential growth with particle number, is converted into a non-intertextual inequality using the above method, the maximum violation of the inequality is the same as before, but the required dimension of the Hilbert space is smaller than the dimension of the original Bell inequality. Further results show that this phenomenon of “condensation” of intertextuality from non-localized associations to monomeric high-dimensional associations is widely present in a class of non-localized associations discovered by the research group in the early stage.

In terms of experiments, the research group developed spatial light modulation technology to achieve high-fidelity quantum state preparation and measurement in a 7-dimensional quantum system based on photonic spatial mode coding, so that on the basis of ensuring no disturbance between the before and after measurements, the violation of the non-intertextual inequality converted from the three-body MABK inequality exceeded 68 standard deviations, and the ratio of the quantum violation value to the classical limit reached 0.274, setting a record for the highest ratio in the intertextuality experiment of monomeric systems.

According to the researchers, the discovery of quantum intertext enrichment not only lays the foundation for more observations of singular quantum associations, but also is expected to promote the final realization of universal quantum computing in various physical systems. (Source: Wang Min, China Science News)

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