After a quarter-century of investigation, a fundamental question about the nature of quantum entanglement has been answered. Julio I de Vicente from Universidad Carlos III de Madrid in Spain has shown that maximally entangled mixed states for a fixed spectrum do not always exist, challenging long-standing assumptions in quantum information theory.
The Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna, Austria, had listed the question as one of their open problems. It essentially asked whether a quantum system can maintain its maximally entangled state in a realistic scenario with noise present.
De Vicente’s study published in Physical Review Letters concludes that there is no universally maximizing all entanglement measures across all states with the same spectrum for certain rank-2 mixed states.
Entanglement is crucial for various quantum technologies, and a maximally entangled state is an especially valuable resource. The concept of maximally entangled mixed states (MEMS) is a departure from traditional views of entanglement, which have primarily associated it with pure states.
MEMS are robust entanglement even in less-than-ideal conditions, making them particularly valuable for technologies like quantum encryption and computing. De Vicente’s result has introduced new questions, such as the conditions needed to simultaneously optimize various entanglement measures within a system.
The implications of this research extend beyond theoretical physics, enabling better control and manipulation of quantum states. This could revolutionize how we approach problems in quantum mechanics, from computing to material science.
Source: https://physicsworld.com/a/open-problem-in-quantum-entanglement-theory-solved-after-nearly-25-years/