EPJ D Highlight - Quantifying how much quantum information can be eavesdropped

Eavesdropping. Credit: Photo by Dmitry Ratushny on Unsplash

New study yields more precise characterisation of monogamous and polygamous entanglement of quantum information units

Encrypted communication is achieved by sending quantum information in basic units called quantum bits, or qubits. The most basic type of quantum information processing is quantum entanglement. However, this process remains poorly understood. Better controlling quantum entanglement could help to improve quantum teleportation, the development of quantum computers, and quantum cryptography. Now, a team of Chinese physicists have focused on finding ways to enhance the reliability of quantum secret sharing. In a new study published in EPJ D, Zhaonan Zhang from Shaanxi Normal University, Xi'an, China, and colleagues provide a much finer characterisation of the distributions of entanglement in multi-qubit systems than previously available. In the context of quantum cryptography, these findings can be used to estimate the quantity of information an eavesdropper can capture regarding the secret encryption key.

Physicists working on new ways of securing quantum encrypted messages are exploiting the fact that, at the quantum scale, a given qubit can only be entangled with one other qubit; this unique trait is referred to as monogamy of entanglement. In practical terms, the quantum rules for entanglement are explained by considering three qubits, called A, B and C, belonging to Alice, Bob and Charlie, respectively. If Alice and Bob share quantum information via a two-qubit system, called AB, they cannot share any entangled states with Charlie’s qubit C.

However, there is also another kind of entanglement, called polygamy, in which qubits display partial entanglement with several qubits at the same time.

In this study, the authors develop a series of equations explaining the conditions for monogamy and polygamy, which are much better characterised than previous work. Specifically, they first investigate three-qubit systems under certain restrictions and then derive a general result for multi-qubit systems.

Z. Zhang, Y. Luo, and Y. Li (2019), Tighter monogamy and polygamy relations in multiqubit systems, European Physical Journal D 73: 13, DOI: 10.1140/epjd/e2018-90563-2

In 2012 we organized the International Conference on Nuclear Structure and Related Topics (NSRT12). Among several offers for publishing the Proceedings we have chosen the open-access journal EPJ Web of Conferences and have not been disappointed. Since this was our first experience with the on-line publication we had many questions to the editorial staff and several times changed our mind. And always we got prompt, exhaustive and patient answers and instructions. We were fully satisfied with the final quality of publication when it has appeared on the website. So our experience in collaboration with the journal is encouraging without any doubts.

Prof. Andrej I. Vdovin, Joint Institute for Nuclear Research, Russia
Member of the Organizing Committee NSRT12, EPJ Web of Conferences vol.38, 2012

ISSN: 2100-014X (Electronic Edition)

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