Formation of two-ion crystals by injection from a Paul-trap source into a high-magnetic-field Penning trap

Two-ion crystals constitute a platform for investigations of quantum nature that can be extended to any ion species or charged particle provided one of the ions in the crystal can be directly laser cooled and manipulated with laser radiation. This paper presents the formation of two-ion crystals for quantum metrology in a 7-tesla open-ring Penning trap. 40Ca+ ions are produced either internally by photoionization or externally in a (Paul-trap) source, transported through the strong magnetic field gradient of the superconducting solenoid, and captured in-flight with a mean kinetic energy of a few electronvolts with respect to the minimum of the Penning-trap potential well. Laser cooling of the two-ion crystal in a strong magnetic field towards reaching the quantum regime is also presented, with particular emphasis on the cooling of the radial modes.Spanish Government PID2019-104093GB-I00/AEI/10.013 39/501100011033Andalusian Government P18FR-3432 PTA2018-016573-IFondo Operativo FEDER A-FQM-425-UGR18Spanish Government FPU17/02596University of Granada "Plan Propio -Programa de Intensificacion de la Investigacion" PP2017-PRI.I-04Laboratorios Singulares 2020European Research Council (ERC) European Commission 278648TRAPSENSOR MICINN/FEDER/UGR FPA2015-67694-P FPA2012-32076 UNGR10-1E501 UNGR13-1E-1830 EQC2018-005130-PJunta de AndaluciaEuropean Commission IE-5713 IE2017-5513Spanish MICINN ("Beatriz Galindo" Fellowship) BEAGAL18/00078German Research Foundation (DFG)European Commission SFB/CRC 122