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Thank you, CTOnews.com netizens. Hello, rabbit clue delivery! CTOnews.com, May 10 / PRNewswire-FirstCall-Asianet /-- Quantum Precision Measurement is committed to applying the principles of quantum mechanics to various measurement tasks to achieve measurement accuracy that exceeds the classical limit. The Heisenberg limit is considered to be the ultimate limit that can be achieved using quantum methods and resources.

Li Chuanfeng and Chen Geng, a team of academicians from the University of Science and Technology of China, worked with their counterparts to achieve quantum precision measurements that exceed the Heisenberg limit precision by using quantum uncertain causal order.

The researchers say the experimental results have an important impact on the understanding of uncertain causal order and quantum precision measurement. At present, the relevant research results have been published in the international journal Natural Physics. CTOnews.com is attached with DOI:10.1038/s41567-023,02046mury.

A schematic diagram of ▲ 's quantum uncertain causal order. The blue and red routes pass through the two gates in different timing and are in a quantum superposition state. Figure source: University of Science and Technology of China in recent years, academia proposed a new quantum structure, that is, quantum uncertain causal order. The superposition principle of quantum mechanics allows not only the superposition of different quantum eigenstates, but also the quantum superposition of two events in two opposite time sequences. It has been proved that such a new type of quantum resource can provide advantages in specific quantum computing and quantum communication tasks. however, the previous work is based on discrete variables and can not be directly applied to quantum precision measurement tasks.

In view of this, the researchers designed a new hybrid (hybrid) quantum device, that is, a discrete qubit is used to control the evolution time sequence of two groups of continuous variables of photons, and the uncertain causal order is realized experimentally, thus realizing the precise measurement of the super-Heisenberg limit of the geometric phase produced by evolution, that is, the uncertainty δ An is inversely proportional to the square of the degree N of the independent evolution process (δ A ∝ 1 / N2).

The experimental results show that this new method achieves the absolute advantage of the highest theoretical measurement accuracy of the causal order method in determining the causal order method, that is, the Heisenberg limit (δ A ∝ 1 / N, the blue dotted line in figure 2). The experimental results approach the theoretical super Heisenberg limit (red solid line below).

The measurement accuracy of ▲ experiment. The black square point is the experimental measurement accuracy of N independent evolution processes, the red solid line is the super Heisenberg limit of the uncertain causal order method (δ Abeli1 / N2), and the blue dotted line is the highest accuracy of the causal order method, namely the Heisenberg limit (δ Abeli1 / N). It is reported that the experiment uses a single photon as a probe, there is no interaction between photons, and the energy required for a single measurement does not exceed the energy of a single photon, thus realizing the first experimental work to exceed the Heisenberg limit under the standardized resource definition. Compared with the method of determining the causal order, the improvement achieved in the experiment can be directly transformed into the practical advantage in the actual measurement task. This experiment has an important influence on the understanding of uncertain causal order and quantum precision measurement.

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