From Quantum State Preparation to Robust Quantum Order

Preparing complex many-body states is a central task for quantum computers, but noise during preparation can fundamentally limit what can be achieved. I will give a broad overview of quantum state preparation, focusing on the role of circuit depth, locality, measurements, and feedback. I will then discuss sequential circuits for preparing long-range ordered states, where local errors can spread into nonlocal defects. I will show how exploiting the structure of the target state’s syndromes can suppress this error propagation using local gates, allowing for a robust preparation of certain symmetry-breaking and topologically ordered states.

Speaker: Frank Pollmann, Professor, Technical University of Munich