New method to acquire the accuracy of quantum metrology

The majority of quantum information tools, including quantum computers, which are considered a level above supercomputers, and quantum communication which cannot be hacked, are based on the principle of quantum entanglement. Nevertheless, entangled systems are present in a small microscopic world, and they are quite tricky.

A diagram of iterative interaction between the quantum system to be measured and the quantum system of the measuring device. Image credit: Pohang University of Science and Technology.

Quantum metrology, offering improved sensitivity compared to traditional measurements in precision metrology, also depended mainly on quantum entanglement, so it is difficult to put it into practice in real-time applications. Recently, a Korean research group suggested an approach to gain precision in quantum metrology without using entangled resources.

A POSTECH research group led by Prof. Yoon-Ho Kim and Dr. Yosep Kim (Department of Physics) has found a low-value amplification (WVA) approach that achieves the Heisenberg limit without using quantum entanglement. The Heisenberg limit refers to the precision that is ultimately achievable in quantum metrology.

WVA-based metrology is one of the approaches to quantify quantum effects. This metrology is a method to obtain as much information as possible about the quantum system with a minimum of effect. It can effectively measure the system without damaging the quantum state.

By using the low value thus measured, it is possible to amplify small physical impacts, such as ultra-small phase shifts. This approach has fewer errors than traditional methods; however, it has a serious limitation of lower detectability.

The use of entanglement offers approaches to overcome this drawback, but the challenge of producing large-scale quantum entanglement has been a big problem when trying to achieve Heisenberg’s bounded metrology.

The team ensured that the Heisenberg limit is reached in low-value amplification, without resorting to entanglement through the iterative interaction between different quantum states. He explains that this is due to the local iterative interactions between each particle of an entangled system and a meter, not to quantum entanglement itself.

Professor Yoon-Ho Kim led the study.

This study will contribute to the practical use of quantum metrology by verifying that entanglement is not an absolute condition to reach the Heisenberg limit..

Professor Yoon-Ho Kim, Department of Physics, Pohang University of Science and Technology

Journal reference:

Kim, Y. et al., (2022) Heisenberg-limited metrology via low-value amplification without using entangled resources. Physical examination letters. doi.org/10.1103/PhysRevLett.128.040503.

Source: https://www.postech.ac.kr/eng/

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