Quantum mechanical effects determine the ultimate sensitivity of optical measurements of length1, position2 and time3, with consequences for applications ranging from biological sensing4 to gravitational wave detection5. Interferometric gravitational wave observatories, in particular, are currently limited through much of the audio frequency band by shot noise due to the quantization of light. Future gravitational wave interferometers will use squeezed light to overcome this measurement noise1. However, the use of squeezed light increases the radiation pressure noise experienced by the mirrors in the interferometer, thus introducing a competing constraint on the measurement precision. Writing in Nature Physics, Jeremy Clark and colleagues experimentally investigate the trade-off between radiation pressure and measurement noise in an electromechanical circuit6.