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New work asserts that a key technique used to probe quantum systems may not be so quantum after all, according to Perimeter postdoctoral researcher Joshua Combes and his colleague Christopher Ferrie.

Over the past 20 years, a strange idea called a "weak value" has taken root in quantum information science.
Many of the things you can do with quantum technologies entail being able to gain information from quantum systems. But there is a quantum conundrum: we can't say what a particle is doing when we're not looking at it, but when we do look at it, we change its behaviour.

But what if we could look "a little"? Well, that's a weak measurement, a concept which is central to the notion of a weak value. The basic idea of weak measurement is to gain a little bit of information about a quantum system by only disturbing it a little bit; by doing this many times, one can ultimately gain quite a bit of information about the system. Weak measurements have applications in quantum information technologies such as quantum feedback control and quantum communications

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