Recent experimental advances have shown that it is possible to detect forces arising from electric fields at a level of aN/ √Hz (atto = 10-18 through coupling of micro or nanofabricated mechanical resonators to a variety of physical systems including single-electron transistors, superconducting microwave cavities, and individual spins. These experiments have allowed for probing studies of the physics of quantum-mechanical backaction and for the development of a new technology base founded on the capability of detecting extremely small external forces. In a host of formats trapped atomic ions have been proposed as ideal candidates for the detection of small forces, including applications in materials science. Using small crystals of 9Be+ in a Penning trap, we demonstrate detection of forces as small as 174 yN (yocto = 10-24) using a crystal of 60 ions. Force detection sensitivity using this crystal is calculated to be 390+/-150 yN/ √Hz using phase-sensitive detection of an externally applied electric field, and we extract a normalized force detection sensitivity of ~50+/-20 yN/ √Hz for n = 1. This result is approximately four orders of magnitude better than previous reports of sensitive force detection due to the small mass of harmonically confined trapped-ion resonators. This technique is based on the excitation of normal motional modes in an ion trap and phase-coherent Doppler velocimetry, which allows for the discrimination of ion motion with amplitudes on the scale of nanometers, and represents a significant advancement in the precision measurement of small forces.
Citation: Nature Physics
Pub Type: Journals
Doppler velocimetry, force sensitivity, ion traps, laser cooling, Penning trap, yocto-Newton