Quantum Optics Seminar by Magdalena Stobinska

Towards experimentally feasible unbounded violation of quantum steering inequality

Quantum steering is a relatively simple test for quantumness of correlations, proving that the values of quantum-mechanical measurement outcomes come into being only in the act of measurement. By exploiting quantum correlations Alice can influence - steer - Bob's physical system in a way inaccessible in classical world, leading to violation of some inequalities. Demonstrating this and similar quantum effects for systems of increasing size, approaching even the classical limit, is a long-standing challenging problem, also because it is not known how to avoid increasing number of measurement settings. Here we provide the first experimentally feasible formulation of unbounded violation of a steering inequality. We achieve it by generalizing the concept of mutual unbiasedness of bases and applying it to the multi-particle bipartite Bell-state. However, our method is general. It opens the possibility of employing multi-particle bipartite steering for randomness certification and development of quantum technologies, e.g. random access codes.