Homodyne monitoring of post-selected decay

Homodyne measurement of the radiative decay of a quantum emitter can be used to track quantum evolution, yielding stochastic quantum trajectories for the emitter’s state. Here we explore how post-selection alters the quantum state dynamics of radiative decay, showing how the probability of finding the emitter in the excited state is modified with post-selections at a final time T. We use experimental data based on phase sensitive amplification of the fluorescence from a superconducting qubit to observe anomalous weak values in continuous weak measurement for certain pre- and post-selected states. We further study the quantum trajectories for certain pre- and post-slected states and and find that these trajectories are confined to deterministic regions in the Bloch sphere.