The Quantum Theory That Peels Away the Mystery of Measurement

Quanta Magazine ^ | 7/3/19 | Phillip Ball

[LibWhacker]

There it is. Don't ask me to explain it because I can't.

Some interesting comments at the source. I read them hoping they would help clear up some things for me, but they actually made it worse, lol. ymmv

[devane617]

Let me digest for a few.

[Deaf Smith]

QTT discovers statistical modeling.

[I want the USA back]

Some people think a cat shoved into a box can be both alive and dead at the same time. It is impossible for a logical person to have a conversation with those people.

I operate under the principle that a statement is either true or false, and that there is no middle ground between true and false. There is no basis for common understanding with people who reject that principle, and so it is impossible to talk with them about anything.

[Larry Lucido]

I was just saying that at a cocktail part last night.

Until everybody walked away.

[Moonman62]

QTT, however, can take back-action into account. The catch is that, to apply QTT, you need to have nearly complete knowledge about the behavior of the system you’re observing. Normally, an observation of a quantum system overlooks a lot of potentially available information: Some emitted photons get lost in their environment, say. But if pretty much everything is measured and known about the system — including the random consequences of the back-action — then you can build feedback into the measurement apparatus that will make continuous adjustments to compensate for the back-action. It’s equivalent to adjusting the telescope’s orientation to keep the planet in the center.

...

They must keep track of effects that go backwards in time.

See Wheeler’s delayed choice experiment:

https://en.wikipedia.org/wiki/Wheeler%27s_delayed-choice_experiment

[Moonman62]

The catch is that, to apply QTT, you need to have nearly complete knowledge about the behavior of the system you’re observing.

...

The key is complete knowledge of the system.

[Track9]

It means if “you are one with the cat”, you’ll know if it’s dead or not.

[exDemMom]

We simply do not know if the cat is alive or dead until we open the box.

I read a story once where a team set up a Schrödinger’s cat experiment, and when they opened the box, found that the cat had disappeared (he did not like being shut into a box).

This article implies that we should be able to predict with high certainty whether the cat will be alive or dead. I don’t see where the uncertainty is being eliminated, just that correction factors are being applied.

[mdmathis6]

It is a true statement that barring direct observation of data, the cat Might be alive or Might be dead, but it is certainly never true that it can be both.

It is modeling along those lines of thinking, that we are seeing breakthru’s on quantum computing(which is up to 8 Qbits now when last I checked). Shrodinger’s cat paradox has often been taken to ridiculous extremes, it’s more about predicted behavior of subparticles as various points in time and how to corral such behaviors into doing useful work such as creating extremely fast and powerful computers with them.

[sasquatch]

Heisenberg moved the cat. Or maybe the box.

[mjp]

observations + effects of measurement + feedback = accurate predictions of future path

[MV=PY]

"I operate under the principle that a statement is either true or false, and that there is no middle ground between true and false. There is no basis for common understanding with people who reject that principle, and so it is impossible to talk with them about anything."

That'll get you through life just fine.

But it turns out that, unfortunately, the real world just isn't that simple.

BTW, great tagline!

[Ezekiel]

Minev and his co-workers were recently able to capture a “quantum leap” — a switch between two quantum energy states — as it unfolded over time.

"That's one small step for man, one giant leap for mankind."

They were also to achieve the remarkable feat of catching such a jump in midflight and reversing it.

Or the remarkable feat of catching a lady in mid-spin and reversing her:

A quantum measurement influences the system being observed: The act of observation injects a kind of random noise into the system. This is ultimately the source of Heisenberg’s famous uncertainty principle. The uncertainty in a measurement is not, as Heisenberg initially thought, an effect of clumsy intervention in a delicate quantum system — a photon striking a particle and pushing it off course, say. Rather, it’s an unavoidable outcome of the intrinsically randomizing effect of observation itself. The Schrödinger equation does just fine at predicting how a quantum system evolves — unless you measure it, in which case the result is unpredictable.

Without the indefinite article, there is no clear distintinction between "man" and "mankind", so you can trick your perception into observing small steps or quantum leaps. Out of many, one.

Acts 2:1 And when the day of the 50th was fully come, they were all with one accord in one place.

It "just so happens" that the Washington Monument is about to reopen with a new elevator system. Nothing random about that.

Living parables for the win!

[BipolarBob]

So it was you. We all asked each other how you got invited to the party and no one knew.

/jk

[Larry Lucido]

:-)

I figured it was because they brought out those little sandwiches...

[glorgau]

Kinda makes sense. If you have a tightly bound system of the very smallest things, using any of those smallest things to provide a “measurement” is going mess with the alignment of the entire system. Hence the “collapse of the wave function.”

[Moonman62]

The twirling lady is a good demonstrator of cognitive bias.

[aquila48]

“The key is complete knowledge of the system.”

If you know that a priori why do you need to measure anything?

[aquila48]

“the cat Might be alive or Might be dead, but it is certainly never true that it can be both.”

Was the cat sick before he got put in the box? Was there food and water in the box?