## Abstract

The famous “quantum jump” of an atom from one level to another was first postulated by Bohr in 1913, nearly 100 years ago. Can there still be anything interesting to say about quantum jumps in a two-level atom today, 100 years later? Of course my answer is “yes”, as I will be talking about two recent papers in this area [1,2]. The most recent [2] proposes experiments to definitively prove that quantum jumps are not due to emission of a photon, but rather to detection. Such a test is possible because different types of detection lead to different types of jumps. The other [1] shows that this flexibility in causing jumps of different types can always be used creatively to make an atom jump between a two fixed states, although in general these are NOT orthogonal.

[1] R. Karasik and H. M. Wiseman, How Many Bits Does It Take to Track an Open Quantum System?

Phys. Rev. Lett. 106, 020406 (4
pages) (2011).

[2] Howard M. Wiseman and Jay M. Gambetta, Are
Dynamical Quantum Jumps Detector-Dependent?

Phys. Rev. Lett. 108, 220402 (5
pages) (2012).

PLEASE NOTE NON STANDARD DAY.