Optical amplification and mass sensing in a spin qubit-nanomechanical resonator hybrid system

Highly sensitive mass sensors are pivotal for precision measurements but face critical challenges, necessitating innovative designs and approaches. In this study, we propose a tunable optical mass sensor based on a hybrid system consisting of a spin qubit and a nanomechanical resonator (NR). The results show that pump field frequency adjustment switches the four-wave mixing (FWM) spectrum between four/five-peaked structures, with two sharp sidebands aligned to the NR's resonance frequency. Near the bistable threshold, pump intensity tuning amplifies the FWM signal by up to 7.53 × 10⁴ times (200 kHz vs. 1 kHz spin-NR coupling). Detecting NR resonance frequency shifts induced by tiny adsorbed analytes (e.g., <i>Escherichia coli</i>, influenza viruses, and HIV virions), the sensor achieves a frequency resolution of 2.52 Hz and a mass resolution of 9.03 fg at 300 K (thermal noise included). These findings provide a fascinating route for high-performance on-chip sensors and advance precision measurement.