Squeezing of quantum and classical fluctuations of one of the quadratures of a vibrational mode enables using this quadrature for high precision measurements. Conventionally squeezing is detected by mixing the mode vibrations with a known signal in homodyne detection. In this paper we demonstrate a different approach to revealing and characterizing squeezing. Using a resonantly driven nonlinear nanomechanical resonator with a high quality factor, we show that classical fluctuations about the stable states of forced vibrations are squeezed and that the squeezing can be measured directly by studying the power spectrum of these fluctuations. The measurement does not require any additional signal. Our experimental and theoretical results are in excellent agreement. They directly extend to the quantum domain and demonstrate an unconventional aspect of squeezing.publishe
