Formation of Two-Ion Crystals by Injection from a Paul-Trap Source into a High-Magnetic-Field Penning Trap

TL;DR

This paper demonstrates the formation and laser cooling of two-ion crystals in a high-magnetic-field Penning trap, advancing quantum metrology capabilities with ions transported from a Paul trap source.

Contribution

It introduces a method to form and cool two-ion crystals in a 7-tesla Penning trap using ions from a Paul trap source, enabling quantum experiments in strong magnetic fields.

Findings

Successful formation of two-ion crystals in a high magnetic field.

Effective laser cooling of radial modes in the Penning trap.

Transport of ions from a Paul trap source into a high-field Penning trap.

Abstract

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. $^{40}$Ca$^+$ 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.