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3. The No-Cloning Theorem and the No-Summoning Theorem
About this Lecture
In this mini-lecture, we introduce the No-Cloning Theorem and the Relativistic No-Summoning Theorem. The No-Cloning Theorem says that, according to quantum theory, it is impossible to make a reliable copy of an unknown polarisation state. The Relativistic No-Summoning Theorem says that if you’re given a light pulse with an unknown polarisation state and want to ‘summon it,’ that is produce a copy of it at one of two points in spacetime (call them Q0 and Q1) where Q0 and Q1 lie outside each other’s light cone (i.e. no information or light can pass between them), then you cannot to so if you do not know in advance whether you want to summon the state at Q0 or Q1.
In this course, Professor Adrian Kent (University of Cambridge) explores relativistic and quantum cryptography. In the first mini-lecture, we introduce the key principles in the Special Theory of Relativity and in Quantum Theory that are needed to understand the cryptographic schemes used in subsequent videos. In the second mini-lecture, we discuss the polarisation of light and how it can be affected by measurement. In the third mini-lecture, we introduce the No-Cloning Theorem and the Relativistic No-Summoning Theorem. In the fourth mini-lecture, we explore the concept of bit commitment. In the fifth mini-lecture, we discuss how to use one-time pads to encrypt messages and prevent eavesdropping. In the sixth mini-lecture, we introduce the BB84 (Bennett-Brassard, 1984) quantum key distribution protocol, which utilises polarisation states to encrypt messages.
Adrian Kent is Professor of Quantum Physics in the Department of Applied Mathematics and Theoretical Physics (DAMTP) at the University of Cambridge. He is also a member of the Cambridge Centre for Quantum Information and Foundations and a Distinguished Visiting Research Chair at the Perimeter Institute for Theoretical Physics. His principal research interests are in quantum foundations, quantum information theory, and quantum cryptography. He is a pioneer in the field of relativistic quantum cryptography, having provided the first relativistic cryptography protocols for bit commitment and ideal coin tossing that achieve unconditional security in 1999. He has published papers extensively on this topic as well as other topics such as quantum key distribution. Professor Kent is a co-editor of the book Many Worlds?: Everett, Quantum Theory, and Reality (2010).
Cite this Lecture
Kent, A. (2022, January 13). Relativistic and Quantum Cryptography - The No-Cloning Theorem and the No-Summoning Theorem [Video]. MASSOLIT. https://massolit.io/courses/relativistic-and-quantum-cryptography/the-no-cloning-theorem-and-the-no-summoning-theorem
Kent, Adrian. "Relativistic and Quantum Cryptography – The No-Cloning Theorem and the No-Summoning Theorem." MASSOLIT, uploaded by MASSOLIT, 13 Jan 2022, https://massolit.io/courses/relativistic-and-quantum-cryptography/the-no-cloning-theorem-and-the-no-summoning-theorem