  While there is a rigorously proven relationship about uncertainties intrinsic
to any quantum system, often referred to as "Heisenberg's Uncertainty
Principle," Heisenberg originally formulated his ideas in terms of a
relationship between the precision of a measurement and the disturbance it must
create. Although this latter relationship is not rigorously proven, it is
commonly believed (and taught) as an aspect of the broader uncertainty
principle. Here, we experimentally observe a violation of Heisenberg's
"measurement-disturbance relationship", using weak measurements to characterize
a quantum system before and after it interacts with a measurement apparatus.
Our experiment implements a 2010 proposal of Lund and Wiseman to confirm a
revised measurement-disturbance relationship derived by Ozawa in 2003. Its
results have broad implications for the foundations of quantum mechanics and
for practical issues in quantum mechanics.

Quantum Physics