Wednesday, January 14, 2009

Hardy's Paradox Resolved?

Over the course of nearly two years of work, Steinberg and then-student Jeff Lundeen, now a research associate at the National Research Council of Canada, built a complicated quantum optical experiment and developed new theoretical tools. In essence, they combined Hardy's Paradox with a new theory known as weak measurement proposed by Tel Aviv University physicist Yakir Aharonov, showing that in one sense, one can indeed talk about the past, resolving the paradox. Weak measurement is a tool whereby the presence of a detector is less than the level of uncertainty around what is being measured, so that there is an imperceptible impact on the experiment. "We found that all of the seemingly paradoxical conclusions in Hardy's Paradox can, in fact, be experimentally verified," says Steinberg, "but that the use of weak measurement removes the contradiction."

"Until recently, it seemed impossible to carry out Hardy's proposal in practice, let alone to confirm or resolve the paradox," he says. "We have finally been able to do so, and to apply Aharonov's methods to the problem, showing that there is a way, even in quantum mechanics, in which one can quite consistently discuss past events even after they are over and done. Weak measurement finds what is there without disturbing it."


whoaWhoaWHOAWHOAWHOA!!!!!!!!!!!!!!

That even needs a blink tag.

Now let's see if everyone agrees with what they found.

You can observe and not disturb.

duuuuuuuuuuuuuuuude.

3 comments:

Alden said...

Sure. The key phrase is this:

"Weak measurement is a tool whereby the presence of a detector is less than the level of uncertainty around what is being measured, so that there is an imperceptible impact on the experiment."

The same is true of all systems -- the trick is to create a large number of identical systems, and probe them very lightly to make the delta-x measurement resolution small enough that delta-p doesn't change much as well.

So Heisenberg is fine, and measurement is still measurement.

The Copenhagen interpretation will need to be reexamined carefully, though (at least for some interpretations of it. :)

Will Baird said...

So if I have a plethora of entangled particles...

Alden said...

Do you know what a plethora eeess?