Bennett and Brassard propose BB84, a way to share secret keys using photons

Why it matters

BB84 launched quantum cryptography and won its inventors the 2025 ACM Turing Award. Variants of it now run in real communication networks, over fiber and via satellites.

Related

• First quantum cryptography experiment works over 30 centimeters (Oct 1989)
• Six researchers show how to teleport an unknown quantum state (Mar 29, 1993)

Sources (4)

• arXiv (Bennett and Brassard, scan of the 1984 proceedings paper) Quantum cryptography: Public key distribution and coin tossing
  Primary sourceDec 1984

  “This is a best-possible quality scan of the original so-called BB84 paper as it appeared in the Proceedings of the International Conference on Computers, Systems & Signal Processing, Bangalore, India, pp. 175-179, December 1984.”

• U.S. National Science Foundation Pioneers of quantum information science recognized with 2025 ACM A.M. Turing Award
  Independent coverageMar 18, 2026

  “In 1984, they introduced what became known as the BB84 protocol, an early and foundational method for quantum key distribution.”

• IBM Newsroom IBM Fellow and Quantum Pioneer Charles H. Bennett Receives A.M. Turing Award, Computing's Highest Honor
  Independent coverageMar 18, 2026

  “Two years later, they introduced the first practical quantum cryptography protocol, called “BB84” for “Bennett–Brassard 1984.” The work showed that two parties, i.e. “Alice” and “Bob,” could establish a secret key with security rooted in the laws of physics rather than potentially shaky assumptions about the difficulty of a particular computation.”

• The Quantum Insider ACM A.M. Turing Award Honors Charles H. Bennett And Gilles Brassard for Foundational Contributions to Quantum Information Science
  Independent coverageMar 18, 2026

  “Variants of BB84 have already been implemented in operational quantum communication networks around the world, using both landlines via fiber and free space communication through satellites.”