[1] He returned to New Zealand in 2002[7] to join the University of Auckland, becoming the inaugural Dan Walls Professor of Physics, a position he still holds today.

[4][1][14] In 1976, while Carmichael was still a graduate student, he and his doctoral supervisor Dan Walls published a seminal paper [15][16] that predicted photon antibunching, which led to the experimental demonstration of the quantum nature of light.

[6] Using their newly developed master equation techniques, Walls and Carmichael derived the form of the fluorescence spectrum that agreed with previous experimental results.

[7][6] Carmichael developed quantum trajectory theory (QTT) in the early 1990s,[11][12] around the same time as the separate formulations by Dalibard Castin & Mølmer, and by Zoller, Ritsch & Dum).

QTT fills this gap by offering a way to describe the trajectories of individual quantum particles that obey the probabilities given by the Schrödinger equation.

[1] The mapping from inputs to outputs is provided by a quantum stochastic process that is set up to account for a particular measurement strategy (eg., photon counting, homodyne/heterodyne detection, etc).

[8] QTT addresses the measurement problem in quantum mechanics by providing a detailed description of what happens during the so-called "collapse of the wave function".

The theory suggests that "quantum jumps" are not instantaneous but happen in a coherently driven system as a smooth transition through a series of superposition states.

In their experiment they used a superconducting artificial atom to observe a quantum jump in detail, confirming that the transition is a continuous process that unfolds over time.