Quadrature operators for a harmonic oscillator have the property that they can be measured in a quantum non-demolition way, that is with a precision only limited by the measurement apparatus. This property makes quadrature measurements relevant in quantum sensing, where small signals acting on the harmonic oscillator can be detected by monitoring a quadrature. A topic closely related to quadrature measurements is that of squeezed states, which have reduced uncertainty in one quadrature. Squeezed states are important for enabling quantum sensing and for quantum information and optics in general.
In our recent preprint, we discuss a method to implement quadrature measurements and generate squeezed states. This method is versatile due to the fact that it relies on using a qubit as a detector, an elementary resource available in many physical implementations. This method has promising prospects for experimental implementation with either nanomechamical or electrical resonators.