Coherent Excitation of the 6S1/2 to 5D3/2 Electric Quadrupole Transition in 138Ba+

TL;DR

This paper demonstrates coherent excitation of a forbidden quadrupole transition in a single barium ion, with potential applications in fundamental physics tests and optical frequency standards.

Contribution

It reports the first coherent excitation of the 6S1/2 to 5D3/2 quadrupole transition in 138Ba+ using a stabilized laser.

Findings

Achieved Rabi oscillations with a 3 ms coherence time.

Utilized a 2051 nm laser stabilized via frequency doubling and cavity locking.

Potential for parity non-conservation experiments and optical clocks.

Abstract

The electric dipole-forbidden, quadrupole 6S1/2 <-> 5D3/2 transition in Ba+ near 2051 nm, with a natural linewidth of 13 mHz, is attractive for potential observation of parity non-conservation, and also as a clock transition for a barium ion optical frequency standard. This transition also offers a direct means of populating the metastable 5D3/2 state to measure the nuclear magnetic octupole moment in the odd barium isotopes. Light from a diode-pumped, solid state Tm,Ho:YLF laser operating at 2051 nm is used to coherently drive this transition between resolved Zeeman levels in a single trapped 138Ba+ ion. The frequency of the laser is stabilized to a high finesse Fabry Perot cavity at 1025 nm after being frequency doubled. Rabi oscillations on this transition indicate a laser-ion coherence time of 3 ms, most likely limited by ambient magnetic field fluctuations.