Abrupt energy flipping in a continuously observed Rabi driven quantum bit

• Main Author: Gilbert Reinisch
• Format: Article
• Language: English
• Published: Elsevier 2021-10-01
• Series: Results in Physics
• Online Access: http://www.sciencedirect.com/science/article/pii/S2211379721008238

In the presence of a periodic external drive, the mean value of the energy of a two-level quantum system (or qubit) displays the well-known Rabi oscillatory dynamics that is usually described within the rotating wave approximation. In order to calculate its standard deviation, we get rid of this latter and obtain a huge ratio (of order unity) of standard deviation over mean value. This is due to the large-amplitude high-frequency oscillations of the internal as well as of the overall phase of the two-level system. In presence of continuous measurement of, say, the ground state energy that yields the quantum Zeno effect, the system remains frozen in its ground state as long as the dynamics of the driven system allows its energy to stay within its Rabi standard deviation. When reaching the boundary, the energy suddenly flips over to the excited level in order to stay further within its standard deviation. We model this energy flip by use of parametrized quantum transitions and show that it can be defined as the result of action quantization. We check our theory by recovering the so-called “quantum jumps” published by Minev et al. (2019).