Measurements of one quadrature of an oscillator with precision beyond its vacuum state uncertainty have occupied a central place in quantum physics for decades. A squeezed state of one of the quadratures is a prominent example of a state which provides such precision. One of the first proposals for generation of such a state involves a quantum nondemolition measurement at twice the frequency of the oscillator. We have recently reported the first experimental implementation of this proposal with a magnetic oscillator. It has been widely assumed that sensing with the precision beyond the vacuum state uncertainty in both quadratures is prohibited by the uncertainty principle. We have demonstrated that this limitation can be overcome by entangling of an oscillator with a quantum reference frame with an effective negative mass. In a more general sense, this approach leads to trajectories without quantum uncertainties and to achieving new fundamental bounds on the measurement precision. Progress towards such a measurement on a mechanical oscillator will be reported.
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121 Burton Morgan, Purdue University, West Lafayette, IN