Breakthrough Prize for the Physics of Quantum Information…and of Cells

The idea of ​​using the laws of quantum mechanics for computation was proposed in 1982 by Richard Feynman. But Deutsch—who is at the University of Oxford, UK—is often credited with establishing the conceptual foundations of the discipline. Computer bits that obey quantum principles, such as superposition and entanglement, can carry out some calculations much faster and more efficiently than ones that obey classical rules. In 1985 Deutsch postulated that a device made from such quantum bits (qubits) could be made universal, meaning it could simulate any quantum system. Deutsch framed his proposal in the context of the “many worlds” interpretation of quantum mechanics (of which he is an advocate), likening the process of one quantum computation to that of many parallel computations occurring simultaneously in entangled worlds.

To motivate further work in quantum computing, researchers at the time needed problems that a quantum computer could uniquely solve. “I remember conversations in the early 1990s in which people would argue about whether quantum computers would ever be able to do anything really useful,” says quantum physicist William Wootters of Williams College, Massachusetts, who has worked with Bennett and Brassard on quantum cryptography problems . “Then suddenly Peter Shor devised a quantum algorithm that could indeed do something eminently useful.”

In 1995 Shor, who is now at the Massachusetts Institute of Technology, developed an algorithm that could factorize large integers—decompose them into products of primes—much more efficiently than any known classical algorithm. In classical computation, the time that it takes to factorize a large number increases exponentially as the number gets larger, which is why factorizing large numbers provides the basis for today’s methods for online data encryption. Shor’s algorithm showed that for a quantum computer, the time needed increases less rapidly, making factorizing large numbers potentially more feasible. This theoretical demonstration “immediately injected energy into the field,” Wootters says. Shor has also made important contributions to the theory of quantum error correction, which is more challenging in quantum than in classical computation (see Focus: landmarks—Correcting Quantum Computer Errors).

“Without Deutsch and Shor we would not have the field of quantum computation as we know it today,” says quantum theorist Artur Ekert of the University of Oxford, who considers Deutsch his mentor. “David defined the field, and Peter took it to an entirely different level by discovering the real power of quantum computation and by showing that it actually can be done.”

Data encryption is the topic cited for the award of Bennett (IBM’s Thomas J. Watson Research Center in Yorktown Heights, New York) and Brassard (University of Montreal, Canada). In 1984 the pair described a protocol in which information could be encoded in qubits and sent between two parties in such a way that the information could not be read by an eavesdropper without that intervention being detected. Like quantum computing, this quantum cryptographic scheme relies on entangling qubits, meaning that their properties are interdependent, no matter how far apart they are separated. This “BB84” protocol and similar quantum encryption schemes have now been used for secure transmission of data along optical networks and even via satellite over thousands of kilometers (see Focus: Intercontinental, Quantum-Encrypted Messaging and Video).

In 1993 Bennett and Brassard also showed how entanglement may be harnessed for “quantum teleportation,” whereby the state of one qubit is broadcast to another distant one while the original state is destroyed (see Focus: landmarks—Teleportation is not Science Fiction). This process too has applications in quantum information processing.

“I am really gratified by this award because it recognizes the field of quantum information and computation,” Shor says. Deutsch echoes the sentiment: “I’m glad that [quantum information] is now officially regarded as fundamental physics rather than as philosophy, mathematics, computer science, or engineering.”

Deutsch, Shor, Bennett, and Brassard deserve recognition for their work, and “I’m delighted that they’re getting it,” Wootters says. He notes that their research not only inspired the development of quantum technologies, but also influenced new research in quantum foundations. “Quantum information theory views quantum theory through a novel lens and opens up a new perspective from which to address foundational questions.”

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