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For more than two decades, the standard quantum limit (SQL) has served as a benchmark for researchers involved in ultra-sensitive force and displacement detection. In this thesis, I discuss a novel displacement detection technique which we have implemented that has allowed us to come within a factor of 4.3 from the limit, closer than any previous effort. Additionally, I show that we were able to use this nearly quantum-limited scheme to observe the thermal motion of a 19.7 MHz in-plane mode of a nanomechanical resonator down to a temperature of 56 mK. At this temperature, the corresponding thermal occupation number of the mode was⟨ n th⟩≈ 60. This is the lowest thermal occupation number ever demonstrated for a nanomechanical (or larger) device. We believe that the combination of these two results has important and promising implications for the future study of nanoelectromechanical systems (NEMS …