Tuesday, May 21, 2024

USTC Advances Quantum Science with New Method to Measure Entanglement Levels

Researchers from the University of Science and Technology of China (USTC), in collaboration with international experts, have unveiled a groundbreaking method for quantifying quantum entanglement, enhancing the capabilities of entanglement witnesses. This innovation, published in Physical Review Letters, marks a significant leap in quantum computing and physics.

Professor Yu Sixia and associates from USTC, alongside Professor Xu Zhenpeng from Anhui University and Armin Tavakoli from Lund University, have introduced a refined approach to the standard entanglement witness (EW) procedure to evaluate quantum entanglement across three experimental conditions. Traditionally, EWs have been instrumental in detecting entanglement by distinguishing between entangled and separable states based on their observable quantities. However, their usage has been limited to detection without estimating the actual level of entanglement.

Addressing this limitation, the team has enhanced the EWs to not only detect but also quantify entanglement. By normalizing the EW into a trace distance, they have established a method to gauge the distinguishability between the data from entangled and separable states under identical measurements. This trace distance fundamentally captures the essence of entanglement, enabling it to define the bounds for various entanglement measures effectively.

The research further explores the application of normalized EWs in different scenarios—trusted devices, device-independent, and measurement-device-independent settings—each offering a unique perspective on the entanglement analysis. For instance, in trusted device scenarios, the normalized EW measures the highest possible distinguishability between entangled and separable states, providing a clearer picture of the quantum state’s complexity.

The methodology proves especially beneficial in multipartite systems, where it helps determine the entanglement depth, indicating the minimum number of entangled particles. As the number of particles increases, this approach can approximate the exact value of entanglement, presenting a robust lower bound that converges to the true measure in large systems.

This enhancement of entanglement witnesses has been met with acclaim in the scientific community, recognized for significantly broadening the scope of entanglement measurement techniques. This advancement not only propels forward the field of quantum physics but also potentially benefits the development of quantum computing by providing a more precise tool for assessing quantum systems.

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