Quantum operations with indefinite direction of time

by Prof. Giulio Chiribella (QICI Quantum Information and Computation Initiative, The University of Hong Kong)

Thursday 17 Jun 2021, 13:00 → 14:00 Europe/Stockholm

The standard operational framework of quantum theory is time-asymmetric. This asymmetry reflects the capabilities of ordinary agents, who are able to deterministically pre-select the states of quantum systems, but not to deterministically post-select the outcomes of quantum measurements. However, the fundamental dynamics of quantum particles is time-symmetric, and is compatible with a broader class of operations where pre-selections and post-selections are combined in general ways that do not presuppose a definite direction of time. In this talk I introduce a framework for quantum operations with indefinite time direction, providing an example, called the quantum time flip, where an unknown, time-symmetric process is accessed in a coherent superposition of two alternative time directions. In certain information-theoretic tasks, a hypothetical agent with access to the quantum flip can in principle outperform all agents who operate in a definite time direction. 

Location: https://kth-se.zoom.us/j/62011326633.