In a paper published in the Journal of Statistical Physics in 1980, the American physicist Paul Benioff described what is now called the quantum Turing machine: a model of a computer that operated according to the laws of quantum mechanics. Quantum mechanics is the branch of physics that studies the behaviour of matter and light at atomic and subatomic scales. At these scales, the certainty associated with classical mechanics disappears. Instead of pinpointing a particle’s properties, scientists can only make educated guesses. This uncertainty may sound daunting. But Benioff — and other scientists like the British physicist David Deutsch, American physicist Richard Feynman, and American computer scientist Peter Shor — suggested ways to harness it for computation. Their work eventually became the foundation for one of the contemporary world’s most ambitious technological pursuits, one for which the Government of India sanctioned over Rs 6,000 crore in April 2023. By 2031, the National Quantum Mission (NQM) — whose objectives include building “intermediate-scale quantum computers” — is expected to “make India one of the leading nations in the development of Quantum Technologies & Applications,” according to the Department of Science & Technology website. Beyond hype Beyond nationalistic pride, the possibilities of a quantum computer are tantalising. Among other things, quantum computers are expected to herald a new era in how we simulate molecules and their interactions, secure our digital lives, optimise complex logistical networks, and model natural phenomena that overwhelm even our most powerful supercomputers. However, those in the thick of it warn against hype. “It is worth treating claims you hear in the field with scepticism,” Jason Freidenfelds, spokesperson for Google Quantum AI, the tech giant’s quantum computing research division, said. “To date no one has experimentally demonstrated a commercially relevant problem that can be solved by today’s quantum computers that