Fixing the rotating-wave approximation for strongly detuned quantum oscillators

Periodically driven oscillators are commonly described in a frame corotating with the drive and using the rotating-wave approximation (RWA). This description, however, is known to induce errors for off-resonant driving. Here, we show that the standard quantum description, using the creation and annihilation of particles with the oscillators' natural frequency, necessarily leads to incorrect results when combined with the RWA. We demonstrate this on the simple (quantum) harmonic oscillator and present an alternative operator basis that reconciles the RWA with off-resonant driving. The approach is also applicable to more complex models, where it accounts for known discrepancies. As an example, we demonstrate the advantage of our scheme on a driven quantum Duffing oscillator.

Automated summary

This article discusses the issue of using the rotating-wave approximation to describe periodically driven oscillators, which may lead to incorrect results for off-resonant driving. The authors propose an alternative operator basis that reconciles the rotating-wave approximation with off-resonant driving.