New Delhi, June 11 -- For more than a decade, big tech companies like IBM, Google and Microsoft have been loudly announcing that quantum computers will soon solve tasks that stump today's supercomputers. From simulating molecules for drug discovery to optimizing global logistics, they promised revolutionary breakthroughs, and all that in seconds instead of months and years.

Quantum computers do hold a lot of promise. Two bits in the traditional or classical computers we use in homes and offices today can represent one of four possible states-00, 01, 10, or 11-but only one at a time. In contrast, two quantum bits (qubits) in a quantum computer can represent all four states simultaneously, thanks to superposition and entanglement propertie...