YQI Seminar - Howard Carmichael - University of Auckland - Quantum Trajectories, Decoherence, and What One MIGHT Read from the Environment

Recent experiments with superconducting qubits have dramatically changed the landscape for addressing elementary quantum systems – both in the preparation and measurement of quantum states. Even the reconstruction of individual quantum trajectories is now carried out. In this talk, I first introduce the idea of a “quantum trajectory”, where I contrast the jump trajectory of photon counting with the diffusive trajectory applicable to superconducting qubits. I then explore two applications, one related to the infamous Schrödinger cat and the other to the Bohr–Schrödinger discussion of quantum jumps in 1926; both, in a modern context, illuminate the meaning of that catchword “decoherence”.