Quantum theory says that quantum
particles have wave-like properties and can exist in many places at
once. Why the objects we see around us every day — in what
physicists call the classical world — don't behave this way despite
being made of these very same quantum particles is a deep and
fundamental question in modern physics.
Measuring (observing) a quantum object supposedly forces it to
collapse from a waveform into one position. This collapse, according
to quantum mechanics dogma, is what makes objects "real," but new
verification of "collapse reversal" suggests that we can no longer
assume that measurements alone create reality. It was back in 2006
that physicist Andrew Jordan, at the University of Rochester,
together with Alexander Korotkov, at the University of California,
Riverside, first mooted the possibility of collapse reversal.
Until then, it was believed that the instant a quantum object was
measured it would "collapse" from being in all the locations it
could be, to just one location like a classical object. But Jordan
proposed that it would be possible to weakly measure the particle
continuously, partially collapsing the quantum state, and then
"unmeasure" it, causing the particle to revert back to its original
quantum form, before it collapsed. Jordan's hypothesis suggests that
the line between the quantum and classical worlds is not as sharply
defined as had been long thought, but that it is rather a gray area
that takes time to cross.
Now, in Nature News, Postdoctoral Fellow Nadav Katz
explains how his team put the idea to the test and found that,
indeed, it is possible to take a "weak" measurement of a quantum
particle, triggering a partial collapse. Katz then "undid the
damage," altering certain properties of the particle and performing
the same weak measurement again. The particle was returned to its
original quantum state just as if no measurement had ever been
taken.
Katz contends being able to reverse the collapse "tells us that
we really can't assume that measurements create reality because it
is possible to erase the effects of a measurement and start again."
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Source: University of Rochester
