Colloquium
Colloquium

Quantum Trajectories, Decoherence, and What One MIGHT Read from the Environment

Howard Carmichael

University of Auckland, New Zealand

         
          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 Schrodinger cat and the other to the Bohr-Schr√∂dinger discussion of quantum jumps from 1926; both, in a modern context, illuminate the meaning of that catchword "decoherence."