First quantum cryptography experiment works over 30 centimeters

Why it matters

It moved quantum cryptography from paper to the lab. The team published the results in 1992, and later demonstrations using satellite links have run the same method over more than 1,000 kilometers.

Related

• Bennett and Brassard propose BB84, a way to share secret keys using photons (Dec 1984)

Sources (3)

• Journal of Cryptology Experimental quantum cryptography
  Primary sourceJan 1992

  “We describe results from an apparatus and protocol designed to implement quantum key distribution, by which two users, who share no secret information initially: (1) exchange a random quantum transmission, consisting of very faint flashes of polarized light;”

• Quanta Magazine Quantum Cryptography Pioneers Win Turing Award
  Independent coverageMar 18, 2026

  “They finally got the experiment working in October 1989 — 10 years to the day after Bennett and Brassard’s first meeting in Puerto Rico. Their apparatus demonstrated quantum key distribution across a distance of 30 centimeters.”

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

  “Bennett and then-summer student John Smolin, now an IBM researcher, built the first quantum cryptography apparatus in Bennett’s office, and — joined by Brassard — carried out the first demonstration of BB84 in 1989. They made the custom two-meter-long device out of mirrors, polarizers, and photon detectors and ran it with software written by Brassard and his students.”