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

Quantum physicists Charles Bennett and Gilles Brassard have been honored with the 2025 ACM Turing Award, often dubbed the “Nobel Prize in Computing.” The prestigious award, which carries a $1 million prize, recognizes their pivotal contributions to establishing the foundations of quantum information science and revolutionizing secure communication and computing.

The Turing Award, named after Alan Turing, the British mathematician who laid the mathematical groundwork for computing, is presented by the Association for Computing Machinery (ACM). Bennett and Brassard have been instrumental in shaping quantum information science for over four decades, most notably by developing a quantum cryptography protocol in the 1980s.

Classical cryptography is a cornerstone of modern computer and communication networks, safeguarding everything from business emails to bank transactions. This method relies on encryption algorithms and a secret “key” that the sender uses to scramble a message into an unreadable form for eavesdroppers. The recipient then deciphers the message using the same key and a decryption algorithm. However, the challenge lies in securely distributing the key between the two parties.

Quantum cryptography, or quantum key distribution (QKD), offers a groundbreaking solution to this problem. By leveraging the principles of quantum mechanics, QKD provides an automated method for distributing secret keys through standard communication fibers. This approach is inherently secure, as any attempt to intercept the key would disturb its quantum state, alerting the communicating parties to the intrusion. Additionally, QKD allows for frequent key changes, significantly reducing the risk of key theft.

In 1984, Bennett, then at IBM Research, and Brassard, at the University of Montreal, proposed the first method for distributing secret keys encoded in quantum states. Their “BB84” protocol revolutionized secure communication by representing a bit of information through the polarization state of a single photon. For instance, a “0” could be represented by a horizontally polarized photon, while a “1” would be represented by a vertically polarized photon. The sender transmits a string of polarized single photons to the receiver, who then measures the polarization of each photon.

The BB84 protocol introduced the concept of quantum entanglement, a phenomenon where two or more particles become interconnected in such a way that the state of one particle cannot be described independently of the others, regardless of the distance between them. This property forms the basis of quantum teleportation and quantum computing, further expanding the potential applications of quantum cryptography.

Bennett and Brassard’s work has not only transformed the field of secure communication but has also paved the way for advancements in quantum computing. As quantum computers continue to evolve, their ability to process vast amounts of data exponentially faster than classical computers holds immense promise for fields such as cryptography, drug discovery, and optimization problems.

The Turing Award recognizes Bennett and Brassard’s profound impact on the development of quantum information science, which has reshaped our understanding of computation and communication. Their pioneering work in quantum cryptography has laid the groundwork for a new era of secure data transmission, ensuring the privacy and integrity of information in an increasingly interconnected world.

In conclusion, the 2025 ACM Turing Award, awarded to Charles Bennett and Gilles Brassard, celebrates their groundbreaking contributions to quantum information science. Their development of quantum cryptography and the BB84 protocol has revolutionized secure communication, while their ongoing research has shaped the future of quantum computing. As the world continues to embrace digital transformation, the foundational work of Bennett and Brassard remains a testament to the transformative power of scientific innovation.