Today we have observed the first quantum jumps in the linear Paul trap setup. We cool a single calcium ion via the S1/2 --> P1/2 dipolar transition and detect the scattered 397 nm photons (the “bright” level) with an EMCCD camera and a PMT. Then, we drive the “qubit” S1/2 --> D5/2 quadrupolar transition by means of a 729 nm diode laser locked to a high-finesse cavity.

The D5/2 level is pumped via the 729 nm laser and has a lifetime in the order of 1 s. When this happens, the cooling cycle is interrupted and the fluorescence drops to the background signal (“dark” level). The sudden changes in the signal due to the transition between the “bright” and “dark” levels are called quantum jumps. The attached file depicts the quantum jumps detected by the EMCCD camera with acquisition time of 50 ms.

This achievement paves the way towards the realization of our envisaged experiments, where the coherent manipulation of the quantum state of calcium ion(s) in the linear Paul trap is required.