Beyond The Heisenberg Uncertainty Principle with Negative Mass Oscillators
Quantum oscillators ranging from a collective spin of an atomic
ensemble to a mechanical oscillator to an electrical oscillator are
central in many areas of physics. Generation of interesting quantum
states of such oscillators allows, for example, performing the most
precise measurements. We have recently demonstrated that a squeezed
state of a spin oscillator for which one quadrature has fluctuations
below the ground state level can be generated by a stroboscopic
quantum nondemolition measurement. However, sensing with the precision
beyond the vacuum state uncertainty in both position and momentum,
which appears to be prohibited by the uncertainty principle is
evenmore intriguing. We have demonstrated that this limitation can be
overcome by entangling an oscillator with a reference oscillator
characterized by an effective negative mass. The core idea is to
cancel the measurement back action of the joint measurement on the two
oscillators. Progress with the experimental demonstration of the back
action cancellation for a macroscopic mechanical oscillator and a
reference spin oscillator will be presented. In a more general sense,
this approach leads to trajectories without quantum uncertainties and
to achieving new fundamental bounds on the measurement precision.
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