Wideband electric field quantum sensing via motional Raman transitions

Abstract

Ultrasensitive detection of the frequency, phase and amplitude of radiofrequency electric fields is crucial for applications in radio communication, cosmology, dark matter searches and high-fidelity qubit control. Quantum harmonic oscillator systems, especially trapped ions, offer high-sensitivity electric field sensing with nanometre spatial resolution but are typically restricted to narrow frequency ranges centred around the motional frequency of the trapped-ion oscillator or the frequency of an optical transition in the ion. Here we present a procedure that enables precise electric field detection over an expanded frequency range. Specifically, we use motional Raman transitions in a single trapped ion to achieve sensitivity across a frequency range over 800 times larger than previous approaches. We show that the method is compatible with both quantum amplification via squeezing and measurement in the Fock basis, allowing a demonstration of performance 3.4(2.0) dB below the standard quantum limit. The approach can be extended to other quantum harmonic oscillator systems, such as superconducting qubit–resonator systems. The narrow frequency response of quantum harmonic oscillators typically limits their application in radiofrequency electric field detection. Now motional Raman transitions in trapped ions are shown to enable wideband, high-precision radiofrequency field sensing.