Quantum physicists Charles Bennett and Gilles Brassard win $1m Turing Award

The quantum physicists Charles Bennett and Gilles Brassard have been awarded the 2025 ACM Turing Award “for their essential role in establishing the foundations of quantum information science and transforming secure communication and computing”.

The Turing Award, often referred to as the “Nobel Prize in Computing,” is awarded by the Association for Computing Machinery (ACM) and carries a $1m prize. The award is named after Alan Turing, the British mathematician who formulated the mathematical basis of computing.

For over 40 years, Bennett and Brassard have played a crucial role in the foundations of quantum information science, in particular establing a quantum cryptography protocol in the 1980s.

Classical cryptography today is a vital part of computer and communication networks, protecting everything from business e-mails to bank transactions.

Information is kept secret using an encryption algorithm together with a secret “key” that the sender uses to scramble a message into a form that cannot be understood by an eavesdropper. The recipient then uses the same key with a decryption algorithm to read the message.

The issue with standard encryption is that the key must be known to both parties with the problem being how to distribute the key securely.

Quantum cryptography, or quantum key distribution (QKD), however, provides an automated method for distributing secret keys using standard communication fibres. Based on the principles of quantum mechanics, QKD is inherently secure and allows the key to be changed frequently, reducing the threat of key theft.

The first method for distributing secret keys encoded in quantum states was proposed in 1984 by Bennett working at IBM Research and Gilles Brassard at the University of Montreal.

In their “BB84” protocol, a bit of information is represented by the polarization state of a single photon – “0” by horizontal and “1” by vertical, for example. The sender transmits a string of polarized single photons to the receiver and by carrying out a series of measurements they are able to establish a shared key and to test whether an eavesdropper has intercepted any information en-route.

The BB84 protocol not only tests for eavesdropping, but also guarantees that sender and reciever can establish a secret key even if an eavesdropper has determined some of the bits in their shared binary sequence, using a technique called “privacy amplification”.

In 1993 Bennett and Brassard along with other collaborators, introduced the concept of quantum teleportation, demonstrating how an arbitrary quantum state could be transmitted between distant parties using quantum entanglement and classical communication.

Subsequent work by the duo also led the development of scalable quantum communication, an effort that continues today. “Bennett and Brassard fundamentally changed our understanding of information itself,” notes ACM president Yannis Ioannidis. “Their insights expanded the boundaries of computing and set in motion decades of discovery across disciplines. The global momentum behind quantum technologies today underscores the enduring importance of their contributions.”

 A life in science

Bennett was born on 7 April 1943 in New York, US.  After earning his Bachelor’s degree from Brandeis University in 1964 and his PhD from Harvard University in 1971, he moved to Argonne National Laboratory. In 1972, Bennett joined IBM Research where he has remained since.

Brassard was born on 20 April 1955 in Montreal, Canada. He earned his Bachelor’s and Master’s degrees from the University of Montreal and his PhD in theoretical computer science from Cornell University in 1979. He then joined the faculty of the University of Montreal shortly thereafter where he has remained since.

As well as the Turing Prize, both Brassard and Bennett has been awarded the Wolf Prize in Physics, the Micius Quantum Prize as well as the Breakthrough Prize in Fundamental Physics.

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