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Relativistic and Quantum Cryptography

1. Special Relativity and Quantum Theory in Cryptography

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In this mini-lecture, we introduce some key principles in Special Relativity and Quantum Theory, focusing in particular on: (i) the fact that information cannot be sent faster than the speed of light (from Special Relativity); (ii) space vs. time graphs that illustrate light cones which limit where information can be sent; (iii) the unintuitive nature of physics on very small scales (Quantum Theory) and how measurement/observation generally alters the measured physical state; (iv) the wave-particle nature of light as seen in the classic double-slit experiment and G.I. Taylor’s modified version of the experiment with very dim light: (v) a demonstration of a diffraction pattern using a laser pointer and diffraction grating; and (vi) a video displaying the wave-particle nature of electrons.


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

APA style

Kent, A. (2022, January 13). Relativistic and Quantum Cryptography - Special Relativity and Quantum Theory in Cryptography [Video]. MASSOLIT.

MLA style

Kent, Adrian. "Relativistic and Quantum Cryptography – Special Relativity and Quantum Theory in Cryptography." MASSOLIT, uploaded by MASSOLIT, 13 Jan 2022,

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