Quantum lock-in force sensing using optical clock Doppler velocimetry

• Published in: Nature communications Vol. 8; no. 1; p. 14157
• Main Authors: Shaniv, Ravid, Ozeri, Roee
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10-02-2017; Nature Publishing Group; Nature Portfolio
• Subjects: 140/125; 639/766/483/1139; 639/766/483/1255; 639/766/930; Doppler effect; Humanities and Social Sciences; Lasers; Measurement techniques; multidisciplinary; Oscillators; Science; Science (multidisciplinary); Sensors
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14157

Force sensors are at the heart of different technologies such as atomic force microscopy or inertial sensing. These sensors often rely on the measurement of the displacement amplitude of mechanical oscillators under applied force. The best sensitivity is typically achieved when the force is alternating at the mechanical resonance frequency of the oscillator, thus increasing its response by the mechanical quality factor. The measurement of low-frequency forces, that are below resonance, is a more difficult task as the resulting oscillation amplitudes are significantly lower. Here we use a single-trapped
88
Sr
+
ion as a force sensor. The ion is electrically driven at a frequency much lower than the trap resonance frequency. We measure small amplitude of motion by measuring the periodic Doppler shift of an atomic optical clock transition, enhanced using the quantum lock-in technique. We report frequency force detection sensitivity as low as 2.8 × 10
−20
 NHz
−1/2
.
Existing force sensors are designed for driving frequencies above tens of kHz due to heating and sensitivity loss. Here the authors demonstrate precise force metrology for below kHz frequency range by combining the Doppler-shifted optical transition in trapped ion and quantum lock-in technique.