Free Republic
Browse · Search
General/Chat
Topics · Post Article

Skip to comments.

Physicists scoop information from Schrodinger's cat box [Quantum Mechanics]
Christian Science Monitor ^ | January 21, 2014 | Eoin O'Carroll

Posted on 01/22/2014 2:53:50 PM PST by ETL

In a paper published in the current issue of the scientific journal Nature Communications and titled "Direct measurement of a 27-dimensional orbital-angular-momentum state vector," a team of physicists led by the University of Rochester's Mehul Malik describe how they circumvented a basic principle of uncertainty that requires that some states of a quantum system must be understood poorly if other states are to be understood well.

Determining a quantum state, such as the position of an electron or the momentum of a photon, is tricky, to say the least. That's because subatomic particles behave nothing at all like billiard balls, orbiting moons, or any other kind of object with which we humans are remotely familiar.

A photon, for instance, sometimes acts like a wave, diffracting, interfering, and scattering, as all good waves ought to. Yet sometimes it will also behave like a particle, for instance by bashing into an electron or by traveling with ease through a vacuum.

According to our current understanding, things at the quantum scale can exist simultaneously in these two modes, both as localized particles, with distinct measurable states, and as spread-out probabilistic waves, with multiple contradictory states.

One consequence of this "wave-particle duality" is that it imposes a fundamental limit on how much we can know about the universe. An unobserved electron, say scientists, exists as a wave of mutually contradictory states. As the German physicist Werner Heisenberg first pointed out in 1927, taking a measurement of one state, say, the electron's position, and you irreversibly alter its momentum, and vice versa. In the parlance of quantum physicists, the "wavefunction" of a system's probabilities "collapses" into a specific state when you observe it.

If the quantum-mechanical model sounds bizarre, that's because it is.

(Excerpt) Read more at csmonitor.com ...


TOPICS: Science
KEYWORDS: erwinschrdinger; quantummechanics; schrodinger; schrodingerscat; schrodingerslitter; stringtheory; uncertaintyprinciple
Navigation: use the links below to view more comments.
first previous 1-2021-4041-6061-8081-87 next last
To: Chode

“how can observing it(under the assumption it means with your eyes) change it’s state??? “

“Observation” necessarily implies something (e.g. a photon of light) interacts with it, thereby changing its state.


21 posted on 01/22/2014 3:21:05 PM PST by rightwingcrazy
[ Post Reply | Private Reply | To 15 | View Replies]

To: Chode
stooopid question #1, i understand how actually measuring/metering could alter an objects state, but... how can observing it(under the assumption it means with your eyes) change it's state??? or is he using the words interchangeably?

From the info provided in Post 2:

What is Schroedinger's Cat?

Answer: Erwin Schroedinger was one of the key figures in quantum physics, even before his famous "Schroedinger's Cat" thought experiment. He had created the quantum wave function, which was now the defining equation of motion in the universe, but the problem is that it expressed all motion in the form of a series of probabilities ... something which goes in direct violation to how most scientists of the day (and possibly even today) like to believe about how physical reality operates.

Schroedinger himself was one such scientist and he came up with the concept of Schroedinger's Cat to illustrate the issues with quantum physics. Let's consider the issues, then, and see how Schroedinger sought to illustrate them through analogy.

Quantum Indeterminancy

The quantum wave function portrays all physical quantities as a series of quantum states along with a probability of a system being in a given state. Consider a single radioactive atom with a half-life of one hour.

According to the quantum physics wave function, after one hour the radioactive atom will be in a state where it is both decayed and not-decayed. Once a measurement of the atom is made, the wave function will collapse into one state, but until then, it will remain as a superposition of the two quantum states.

This is a key aspect of the Copenhagen interpretation of quantum physics - it's not just that the scientist doesn't know which state it's in, but it's rather that the physical reality is not determined until the act of measurement takes place. In some unknown way, the very act of observation is what solidifies the situation into one state or another ... until that observation takes place, the physical reality is split between all possibilities.

On To The Cat

Schroedinger extends this by proposing that a hypothetical cat be placed in a hypothetical box. In the box with the cat we would place a vial of poison gas, which would instantly kill the cat. The vial is hooked up to an apparatus which is wired into a Geiger counter, a device used to detect radiation. The aforementioned radioactive atom is placed near the Geiger counter and left there for exactly one hour.

If the atom decays, then the Geiger counter will detect the radiation, break the vial, and kill the cat. If the atom does not decay, then the vial will be intact and the cat will be alive.

After the one-hour period, the atom is in a state where it is both decayed and not-decayed. However, given how we've constructed the situation, this means that the vial is both broken and not-broken and, ultimately, according to the Copenhagen interpretation of quantum physics the cat is both dead and alive.

Interpretations of Schroedinger's Cat

Stephen Hawking is famously quoted as saying "When I hear about Schroedinger's cat, I reach for my gun." This represents the thoughts of many physicists, because there are several aspects the thought experiment that bring up issues. The biggest problem with the analogy is that quantum physics typically only operates on the microscopic scale of atoms and subatomic particles, not on the macroscopic scale of cats and poison vials.

The Copenhagen interpretation states that the act of measuring something causes the quantum wave function to collapse. In this analogy, really, the act of measurement takes place by the Geiger counter. There are scores of interactions along the chain of events - it is impossible to isolate the cat or the separate portions of the system so that it is truly quantum mechanical in nature.

By the time the cat itself enters the equation, the measurement has already been made ... a thousand times over, measurements have been made - by the atoms of the Geiger counter, the vial-breaking apparatus, the vial, the poison gas, and the cat itself. Even the atoms of the box are making "measurements" when you consider that if the cat falls over dead, it will come in contact with different atoms than if it paces anxiously around the box.

Whether or not the scientist opens the box is irrelevant, the cat is either alive or dead, not a superposition of the two states.

Still, in some strict views of the Copenhagen interpretation, it is actually an observation by a conscious entity which is required. This strict form of the interpretation is generally the minority view among physicists today, although there remains some intriguing argument that the collapse of the quantum wavefunctions may be linked to consciousness. (For a more thorough discussion of the role of consciousness in quantum physics, I suggest Quantum Enigma: Physics Encounters Consciousness by Bruce Rosenblum & Fred Kuttner.)

Still another interpretation is the Many Worlds Interpretation (MWI) of quantum physics, which proposes that the situation actually branches off into many worlds. In some of these worlds the cat will be dead upon opening the box, in others the cat will be alive. While fascinating to the public, and certainly to science fiction authors, the Many Worlds Interpretation is also a minority view among physicists, though there is no specific evidence for or against it.

http://physics.about.com/od/quantumphysics/f/schroedcat.htm

22 posted on 01/22/2014 3:21:57 PM PST by ETL (ALL (most?) of the Obama-commie connections at my FR Home page: http://www.freerepublic.com/~etl/)
[ Post Reply | Private Reply | To 15 | View Replies]

To: Chode
how can observing it
(under the assumption it means with your eyes)
change it's state???

To observe the particle with your eyes requires
bouncing a photon against the particle
that then interacts with you eye.
By bouncing a photon or other particle against it,
the state of the particle is changed.

Some interaction with the particle must occur
before you can perceive it.

23 posted on 01/22/2014 3:23:16 PM PST by HangnJudge
[ Post Reply | Private Reply | To 15 | View Replies]

To: Chode
stooopid question #1, i understand how actually measuring/metering could alter an objects state, but... how can observing it(under the assumption it means with your eyes) change it's state???

After spending a semester in physics (many eons ago) measuring light as a particle, and measuring light as a wave function, I stopped asking those kinds of questions. OTOH, I do think of a situation as a probability cloud, until I learn the actual outcome of the situation, at which point I think of the cloud as having collapsed to the final outcome.

24 posted on 01/22/2014 3:27:12 PM PST by exDemMom (Current visual of the hole the US continues to dig itself into: http://www.usdebtclock.org/)
[ Post Reply | Private Reply | To 15 | View Replies]

To: EBH

#5 with the cat in the rectangle of light is the absolute best


25 posted on 01/22/2014 3:29:06 PM PST by KC Burke (Officially since Memorial Day they are the Gimmie-crat Party.ha)
[ Post Reply | Private Reply | To 5 | View Replies]

To: I want the USA back
If they can’t see the inherent contradiction in saying that something exists simultaneously in two contradictory states, then no power on Earth can help them.

It is actually not a contradiction. Any object (be it an electron or you or a planet) is at once both a wave and a particle. It's just the way G-d set up the universe.

So if you test an electron for wave behavior, it will pass every wave test, perfectly. So an electron must be a wave.

But if you test an electron for particle behavior, it will pass every particle test, perfectly. So an electron must be a particle.

So what is an electron, a wave or a particle? It must be two entirely different things at once. How it shows itself to you just depends on how are are examining it!

26 posted on 01/22/2014 3:30:05 PM PST by Leaning Right (Why am I holding this lantern? I am looking for the next Reagan.)
[ Post Reply | Private Reply | To 19 | View Replies]

To: ETL
i'll take what i can get... 8^)
27 posted on 01/22/2014 3:30:48 PM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
[ Post Reply | Private Reply | To 13 | View Replies]

To: rightwingcrazy
i can observe this thread but not change it's state unless i post to it...

how does seeing something with you eye effect what you see???

28 posted on 01/22/2014 3:33:37 PM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
[ Post Reply | Private Reply | To 21 | View Replies]

To: ETL
thanks, for the post...and the kittens. ;-)

29 posted on 01/22/2014 3:36:52 PM PST by skinkinthegrass (The end move in politics is always to pick up a gun..0'Caligula / 0'Reid / 0'Pelosi)
[ Post Reply | Private Reply | To 1 | View Replies]

To: ETL
Penny proved that Schrodeinger’s cat is alive.


30 posted on 01/22/2014 3:40:08 PM PST by DeFault User
[ Post Reply | Private Reply | To 1 | View Replies]

To: DeFault User

No Penny!!! Not Pajama Boy!


31 posted on 01/22/2014 3:44:24 PM PST by Kirkwood (Zombie Hunter)
[ Post Reply | Private Reply | To 30 | View Replies]

To: HangnJudge
bouncing a photon or other particle against it, the state of the particle is changed.

but aren't photons bouncing off of it anyway whether they go into my eye or not?

i guess my point is, i am not doing anything but looking at it,not trying to measure it - not affecting it in any way, scattered photons of light either enter my eye or they don't through nothing of my doing, if they enter my eye and i see them, how does that change it's state?

that is why i ask is he using the words measure and observe interchangeably

32 posted on 01/22/2014 3:46:17 PM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
[ Post Reply | Private Reply | To 23 | View Replies]

To: ETL

Affirming my list subscription. Thanks.


33 posted on 01/22/2014 3:46:20 PM PST by Gene Eric (Don't be a statist!)
[ Post Reply | Private Reply | To 4 | View Replies]

To: rightwingcrazy
true, but the observation of same is not what is altering it's state... yes? i am observing it's change not causing it
34 posted on 01/22/2014 3:48:45 PM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
[ Post Reply | Private Reply | To 21 | View Replies]

To: Chode
how does seeing something with you eye effect what you see???

If rightwingcrazy doesn't mind, I'll take a stab at that.

Imagine that you are a blind person. And you are carrying a sack of baseballs. To tell if something is in front of you, you throw a baseball. If the ball bounces back to you, something is there.

Now suppose a cardboard box is in front of you. You throw a baseball at it. The baseball bounces back to you. But the box will also move! The box will no longer be where it was when the ball hit it. By merely "looking" at the box with your baseball, you have altered the state of the box.

This is what happens every time you look at something in real life. The "baseballs" are particles of light that bounce off the object, then go into your eyes.

So when you are looking at, say, a house, the light from the sun is actually moving the house, just the way your baseball moved the cardboard box. But the house is so big the effect not noticeable.

But electrons are very small. When light particles hit them, they move noticeably. The result is a blur. You cannot be certain just where they are. That's part of the Uncertainty Principle!

35 posted on 01/22/2014 3:49:36 PM PST by Leaning Right (Why am I holding this lantern? I am looking for the next Reagan.)
[ Post Reply | Private Reply | To 28 | View Replies]

To: exDemMom
i'm right there with you...
36 posted on 01/22/2014 3:50:16 PM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
[ Post Reply | Private Reply | To 24 | View Replies]

To: Chode

I’m far from an expert on the subject, but, as the piece I posted a little while ago points out, there are several interpretations of QM.

Interpretations of Schroedinger’s Cat
http://www.freerepublic.com/focus/chat/3114541/posts?page=22#22


37 posted on 01/22/2014 3:50:50 PM PST by ETL (ALL (most?) of the Obama-commie connections at my FR Home page: http://www.freerepublic.com/~etl/)
[ Post Reply | Private Reply | To 32 | View Replies]

To: Leaning Right
but isn't sight passive??? the aperture of my eye is either open or closed and only accepts what goes into it when it's open, it projects nothing... this is where i get lost on his use of the word observation
38 posted on 01/22/2014 3:55:11 PM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
[ Post Reply | Private Reply | To 35 | View Replies]

To: Chode

—how does seeing something with you eye
—effect what you see???

Your eye does not “See” the particle
The Eye “Sees” the photon that was
emitted or bounced against the particle

In this case, the Particle was
“measured” by the incident photon
Your Eye “measured” the incident photon,
not the particle itself


39 posted on 01/22/2014 3:56:07 PM PST by HangnJudge
[ Post Reply | Private Reply | To 28 | View Replies]

To: ETL
thx
40 posted on 01/22/2014 3:56:26 PM PST by Chode (Stand UP and Be Counted, or line up and be numbered - *DTOM* -vvv- NO Pity for the LAZY - 86-44)
[ Post Reply | Private Reply | To 37 | View Replies]


Navigation: use the links below to view more comments.
first previous 1-2021-4041-6061-8081-87 next last

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
General/Chat
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson