Single-ion oscillator with radiative cooling

Vladimir G. Minogin

CONTENTS 1. Introduction 359 2. Ion confinement 360 a. The Penning trap. b. Rf quadrupole trap 3. Principle of radiative ion cooling 361 4. Basic experiments 362 a. Cooling of Mg II ions. b. Cooling of Ba II ions 5. Spectroscopic investigations of trapped ions 364 6. Conclusions 364 References 364

了一 齋藤, Ryoichi Saito

Takashi Mukaiyama

Yen-Wei Lin, S. Williams, Brian Odom

We study the motion of an undamped single-ion harmonic oscillator, resonantly driven with a pulsed radiation pressure force. We demonstrate that a barium ion, initially cooled to the Doppler limit, quickly phase locks to the drive and builds up coherent oscillations above the thermal distribution after scattering of order 100 photons. In our experiment, this seeded motion is subsequently amplified and then analyzed by Doppler velocimetry. Since the coherent oscillation is conditional upon the internal quantum state of the ion, this motional excitation technique could be useful in atomic or molecular single-ion spectroscopy experiments, providing a simple protocol for state readout of nonfluorescing ions with partially closed-cycle transitions.

Pan‐Yu Hou, Jenny J. Wu, Stephen D. Erickson +6 more

Cooling the motion of trapped ions to near the quantum ground state is crucial for many applications in quantum information processing and quantum metrology. However, certain motional modes of trapped-ion crystals can be difficult to cool due to weak or zero interaction between the modes and the cooling radiation, typically laser beams. We overcome this challenge by coupling a mode with weak cooling radiation interaction to one with strong cooling radiation interaction using parametric modulation of the trapping potential, thereby enabling indirect cooling of the former. In this way, we demonstrate near-ground-state cooling of motional modes with weak or zero cooling radiation interaction in multi-ion crystals of the same and mixed ion species, specifically $^9$Be$^+$-$^9$Be$^+$, $^9$Be$^+$-$^{25}$Mg$^+$, and $^9$Be$^+$-$^{25}$Mg$^+$-$^9$Be$^+$ crystals. This approach can be generally applied to any Coulomb crystal where certain motional modes cannot be directly cooled efficiently, including crystals containing molecular ions, highly-charged ions, charged fundamental particles, or charged macroscopic objects.

HERBERT WALTHER