Q What is the basic idea behind quantum cryptography?

In typical communication scenarios, such as transmitting information over a telephone wire, it is difficult to ensure that communication is not intercepted. Quantum mechanics, however, has the potential of detecting eavesdropping. This led Gilles Brassard and me to develop a cryptographic scheme wherein, instead of attempting to send a reliable message, the sender (whom we refer to as “Alice”) transmits a random sequence, while the receiver (whom we call “Bob”) attempts to read them… If there is considerable eavesdropping during the transmission of the encrypted message, the two parties will not be able to reach a consensus on the shared key. Recognising this, the two parties will opt not to use it and will instead attempt the process again the following day.

Q You co-discovered quantum teleportation that involves transporting the state of one particle to a distant particle without sending the particle itself. How did you think of it?

Quantum teleportation grew from a brainstorming session in Montreal, Canada, in 1992, following a talk by Bill Wootters about an earlier work he did with Asher Peres. In that work, it was shown that if two particles are in the same unknown quantum state, that state can be ascertained more reliably by doing joint experiments on the particles together than by experimenting on them in separate locations and exchanging messages. We started wondering how the separated experiments can overcome the handicap of separation. With amazement, we found that the use of an entangled pair of particles enables the experimenter to disembody and then perfectly recreate it in the other lab. We called this process quantum teleportation, though Peres complained about mixing Greek “tele” with Latin “portation”.

Q In 1955, Richard Feynmann wrote: The value of science is the fun called intellectual enjoyment. What do you think?

I too think it is basically fun. When things are originally discovered, nobody knows what they are good for, but they turn out to be good for something else. When the telephone was first invented, it was originally thought to be something not for what the telephone ultimately turned out to be good for. When Faraday was asked about the usefulness of some chemical that he had just discovered, he had no good response to this question. But later when he was asked the same question in connection with electromagnetic induction, he replied to the Chancellor of the Exchequer, “I am not sure what it will be used for, but I’m sure you will tax it”.

Q Why do you think science is important for human society and culture?

There are numerous reasons why adopting a scientific perspective is crucial for solving complex problems in any area of human activity… A true scientist appreciates being proven wrong. Although most scientists are not openly religious, their approach to the natural world mirrors the reverence that religious individuals have for God. This awe before nature is akin to the awe that religious individuals feel before God. I often use Einstein as an example to illustrate the necessity of humility in scientific pursuits. Despite his exceptional capacity for unconventional thinking, Einstein struggled to fully appreciate the beauty of quantum mechanics, demonstrating that even renowned scientists may have limitations in certain areas.

Q What are your thoughts on the nature of human consciousness and the possibility of its scientific study?

The “hard problem of consciousness” is that it is impossible even from a complete physical understanding of a system to say whether it is conscious. It is difficult to explore consciousness meaningfully without appropriately defining it. I believe it is an inherently fuzzy concept. But on a different ethical aspect, I would like to stress that it is best to treat everyone as having rights. The alternative risks a slide down the slippery slope of dehumanisation, treating people of a different tribe as if they have no rights. On the other hand, if one is a powerful megalomaniac, it leads to treating everyone but oneself as having no rights.

Q What are your opinions about the relationship between state and religion? Can scientists do anything to combat fundamentalism?

The authors of the American and Indian constitutions were deeply familiar with the challenges to human cooperation. They recognised that religion often stirs intense emotions and deep divisions. Consequently, both Constitutions assert that individuals should not be restricted by any established dogma except for the imperative to engage constructively with those holding divergent views. When a society loses confidence in pluralism, it becomes more uniform, fragile and vulnerable to authoritarianism.

Though scientists are often viewed as arrogant, telling everyone else what to think, their profession is fundamentally humble. True scientists take a perverse delight in having their own pet beliefs proved wrong, if possible by their own efforts, but if necessary by colleagues. By exemplifying this humility, not only in their work but in everyday life, scientists can help ordinary people become better, more tolerant citizens.