The measurement problem in quantum mechanics has challenged physicists and philosophers for almost a century. It has been a focal point of debate in the philosophy of physics, engaging minds from Richard Feynman to Sir Roger Penrose. We now have a plethora of interpretations. Mario Barbatti argues that, while the quantum measurement problem is not completely solved, the proposed solutions are beginning to bear fruit.

At the World Science Festival held this spring, the renowned physicist Brian Greene engaged in a thought-provoking debate with three quantum mechanics specialists, asking about the quantum measurement problem or what happens to a quantum state when it is measured. It was unsettling to see all three proposing entirely distinct answers. Why, a century after the development of quantum mechanics, do we still lack a consensus on its most fundamental process? What do we truly understand about the quantum measurement problem?