QUROPE Quantum Information Processing and Communication in Europe

Ions confined in radiofrequency (Paul) traps, highlighted by Dave Wineland’s 2012 Nobel Prize, constitute an almost ideal quantum system, in the sense that they can be maintained for long times in a well-controlled environment, virtually free from external perturbations. This makes them attractive for applications such as quantum information processing and high-precision measurements. Two important ingredients in this kind of experiment are the control of the external motion by laser cooling, and of the internal quantum state of the ions.

Our project is to apply these techniques to molecular ions, more specifically to the simplest of them, the molecular hydrogen ion H2+. This species cannot be directly laser-cooled, but it can be sympathetically cooled (through the Coulomb interaction) by laser-cooled beryllium ions. The ions can be produced in a selected internal (ro-vibrational) state by resonant multiphoton ionization (REMPI) of H2. The obtained state-selected, ultracold ion ensemble will be used to perform high-resolution spectroscopy of a two-photon vibrational transition, which will provide a stringent test of molecular QED calculations. Comparison between theory and experiment will lead to an improved determination of a fundamental physical constant, the ratio of the electron and proton masses me/mp.

Ground state sympathetic cooling will also be applied protons (H+) to prepare the cooling of antimatter ions fior the GBAR project.

The proposed PhD work will involve the following tasks:

- operate a new linear Paul trap to demonstrate the trapping of Be+ ions;

- study H2+ ion production by REMPI in a dedicated ion source;

- build the laser source at l = 313nm for Doppler cooling of Be+ ions (intracavity frequency doubling of a 626 nm beam with a BBO nonlinear crystal).

- characterize sympathetic cooling dynamics

- perform H2+ spectroscopy

Collaborations

ComiQ network : training periods + physics schools

Mainz University, F. Schmidt Kaler group, http://www.quantenbit.de/

Amsterdam VU, J. Koelemeij group

GBAR project : http://gbar.in2p3.fr/