Discussion in 'Astronomy, Exobiology, & Cosmology' started by Ivan, Dec 18, 2011.
Probably pointless to provide you with further references.
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Well more references addressing wave particle duality. You have once again failed to address the question, or that is provide the reference requested.
Did you read the whole of those papers? I admit I more or less scanned much of the last one. If there was any reference to any experiment performed that simultaneously measured position and momentum I missed it.
I have not been questioning anything about wave-particle duality. I haven't even questioned the uncertainty principle. I initially just said that it was a measurement issue. That much seems well documented, by all of your references.
The issue you have been avoiding once again is your insistence that position and momentum can be measured at the same time. None of your references so far document any experiment that does so.
At this point it is no longer worth continuing. You are stuck and there is no help for that. You do not even seem to understand what you have posted yourself, let alone the question or challenge before you.
When you can provide an example of an experiment that has measured both at the same time, perhaps then the discussion can continue. Keep in mind the difference between a theoretical treatment of the debate and the reporting of an experiment, which has been undertaken.
The challenge again, in case you forgot.., an experiment where position and momementum have been measured at the same time not just sequentially in the same experiment.
Since at least 2008.
Time-Resolved Detection of
AlexG, that paper is interesting. Since I am not a particle or solid state physisicts, it will take some time and likely more than one read to begin to understand what they are really saying.
At first read it does not seem that any interference pattern is generated, at least directly, from single electrons. These appear to be interpreted results, based on many electrons passing through, over time. What seems more important is the solid state design insures that only one electron at a time can pass through. I don't think the title itself was meant to suggest that an electron was interfering with itself, so much as that only one electron at a time can pass through the essentially solid state double slit.
The interference patterns generated by the data collected still involves many electrons, not just a single electron.
From the following quote, even timimng seems to be interpreted, rather than directly measured.
The interdot transitions are too fast to be detected with the bandwidth of the charge detector (Γdet = 20 kHz), but the coupling energy can still be determined from charge localization measurements.
However, like I said.., I am neither a particle or solid state physisicts, so what the paper seems to be saying when I read it may not be what the authors intended. (I hope any misuse of the term solid state is not a distraction from the intent.)
As references I've already provided you attest, complementarity, of which wave-particle duality is an example, is merely different language for the uncertainty principle. You cannot address one without implicitly addressing the other.
If gravity never gets to zero, can it become 100%, where 1 particle becomes another particle? Say in GR?
Keep in mind that I have been consistently asserting that position and momentum can not be measured at the same time, as in simultaneously. And that I further define the challenged to the simultaneous measurement of position and momentum of a single quantum particle.
The following two quotes are included because they define or restrict the issue to a discussion of single quantum particle events. There has never been a question that where a "beam" of light or group of particles is involved experiments can be designed where both the wave nature can be observed and the path or particle aspect known or determined, after the fact. Even the classical double slit beam type experiments that do demonstrate both characteristics, do not represent simultaneous measurement, which is what I have been objecting to. The slit and path are not collocated with the detector and interference patterns, which support the wave nature, and are only observable for a beam or overtime and a series of single particle events.
The following quotes further define the basis of the disagreement.
From one of your early links,
The uncertainty principle also called the Heisenberg Uncertainty Principle, or Indeterminacy Principle, articulated (1927) by the German physicist Werner Heisenberg, that the position and the velocity of an object cannot both be measured exactly, at the same time, even in theory.
I raised the bar from the start by asking for an example that involves the measurements of a single quantum particle. This was meant to emphasize the simultaneous measurement limitation, rather than be an impossible bar. Even where a beam of light or multiple single particle events are involved the position and wave or momentum measurements or observation do not occur at a single location. Generally position is which of two slits a particle passes through and wave or momentum is measured at a detector screen some distance after the slit(s).
In experiments where an interference pattern is observed and which slit was involved are both known with any degree of certainty, which slit is only determined after the fact not at the time of the particles passing through it. Only where a single particle or photon is involved can position or location be measured at the detector, but in that case there is no observable interference pattern.
The challenge has been to find an experiment where both position and momentum are measured at the same time. By its very nature this excludes a double slit experiment where the slit/location and interference pattern/wave character are not co-located.
The three links you provided are all interesting for different reasons. None of them seem to demonstrate a simultaneous measurement, though in at least one the results suggest and unmeasured simultaneous wave/particle character. Not a new idea.
Your first link, A molecular double-slit experiment with partial “which-way” information, is mostly a description of the classical double slit experiment. It does go on to reference undefined recent experiments that suggest, "experimentally demonstrable conditions where matter appears to be both a wave and a particle."
The following quotes from the link above support these conclusions.
But Bohr’s Complementarity Principle (2), which explains this ambiguity, requires that one can only observe one of the two electron manifestations at any given time - either as a wave or a particle, but not both simultaneously. This remains a certainty in every experiment, despite all the ambiguity in quantum physics...
Recently there has been a set of experiments suggesting that these various manifestations of matter can be "carried over into" each other – in other words, they can be switching from one form to the other and, under certain conditions, back again. This class of experiments is called quantum markers (3) and quantum erasers (4). Researchers have shown in the last few years that for photons and atoms - and now, electrons - "both/and" and "either/or" exist side-by-side. In other words, there is a grey zone of complementarity. There are hence experimentally demonstrable conditions where matter appears to be both a wave and a particle.
The second link, Paradox in Wave-Particle Duality, again an interesting experiment. However, once again it does not involve the measurement of single photons. The interference pattern once again requires multiple single photon events and the double slit detector setup (here the double slits are pin holes) are not collocated so the position and wave character are not simultaneously observed or measured.
In this paper we report on the presence of sharp interference and highly reliable which-way information in the same experimental arrangement for the same photons using non-perturbative measurement techniques at separate spacetime coordinates, both of which refer back to the behavior of the photon at the same event, i.e. the passage through the pinholes.
The third link, Quantitative conditional quantum erasure in two-atom resonance fluorescence, appears to be a theoretical paper.., I did not wade through the entire paper... After working through the first few pages and then skimming the rest, the theoretical nature of the paper can be seen in a sentence from the first paragraph. Note the bold portion below.
We explain how the erasure relation can be violated under these circumstances.
Notice they do not claim that the relation has been violated!
I am not sure I understand what you are actually asking.
In practice I don't believe we can or have observed any gravitational mass that becomes infinite, or 100%. Though the idea of singularities are predicted within GR, if they do exist they would be within the event horizon of a black hole. At present everything within the event horizon is unobservable and remains theoretical.
As a matter of experience there is nothing that suggests that gravity is ever zero or infinite (100%). The closest thing to zero gravity might involve dark energy (still undefined) which can be thought of as repulsive gravity. Even that description is specualtive, since we cannot yet fully define what dark energy is.
OnlyMe, perhaps the 1965 Arthurs-Kelly model will finally appease you. If not, then I'll just have to write you off as hopeless.
Also referenced here:
Most people can simply read the "exactly" in "the position and the velocity of an object cannot both be measured exactly, at the same time, even in theory" to be the determining factor. You've failed to even attempt to address this the many times I've asked you why every reference includes such qualifiers.
Instead, you want to play troll, by throwing it back on others while pretending that you are honestly interested in learning.
This is a situation where we are talking about two separate issues. I have been scratching my head trying to understand why you keep putting so much emphasis on "exactly" and not understanding that I have been talking about the practicality of executing an experiment that measures both position and momentum at the same time.
Nothing I have been presenting has anything to do with an interpretation of the uncertainty principle. It is about the inability to experimentally measure both at the same time in a practical manner.., in practice.
Once again what I have been talking about is the execution of a practical experimental measurement of both position and momentum, at the same time. This is a practical issue of experimental design and technical limitations. Also, I don't see this practical limitation, as invalidating the uncertainty principle, just limiting certain kinds of experimental tests.
The Arthurs-Kelly model does not represent an actual experiment. The second of the two links you just provided, Heisenberg’s Uncertainty Principle, by P. Bush, is actually a very good reference, for both your position and mine. See the following quotes from that paper. Though what I have been trying to present can be found as a general theme in these quotes, the last sentence says it clearly.
ON EXPERIMENTAL IMPLEMENTATIONS AND TESTS OF THE UNCERTAINTY PRINCIPLE
“Turning now to the question of the empirical support [for the uncertainty principle], we unhesitatingly declare that rarely in the history of physics has there been a principle of such universal importance with so few credentials of experimental tests.” (Jammer, 1974, p. 81)
.... Jammer’s verdict still holds true today.
Tests of preparation uncertainty relations
A model independent and thus more direct confirmation of the uncertainty principle can be obtained if the widths of the position and momentum distributions are measured in terms of the overall width defined in Eq. (4)....
It should be noted that these experiments do not, strictly speaking, constitute direct tests of the uncertainty relations for position and momentum observables. While the position uncertainty, or the width of the position distribution, is determined as the width of the slit, the momentum distribution is inferred from the measured position distribution at a later time, namely when the particles hit the detection screen.
On implementations of joint and sequential measurements
To the best of our knowledge, and despite some claims to the contrary, there is presently no experimental realization of a joint measurement of position and momentum....
Turning to the question of position and momentum proper, the Arthurs-Kelly model is particularly well suited to elucidate the various aspects of the uncertainty principle for joint and, as we have seen, sequential joint measurements of approximate position and momentum. However, it is not clear whether and how an experimental realization of this scheme can be obtained.
There have been some claims of success, but for position and momentum, they seem to remain claims.
Nice quote mining. But if you're so enamored with that particular paper, perhaps you should have read its conclusions.
You are doing the same thing as in the past. You are trying to divert the proof to one of examining the uncertainty principle itself.
I was clear in that I was talking about practical simultaneous measurement of position and momentum... And my challenge was to locate any experiment where they were measured, simultaneously. that means measured at the same time, as opposed to measured sequentially.
You still have provided no reference to a simultaneous measurement of position and momentum.
From your posted quote,
"a sequential measurement of measuring first position and then momentum constitutes an instance of a joint measurement of some observables, ..."
What the above portion of your quote is saying is that an experiment can be constructed in such a way the sequential measurements — measurements that are not simultaneous — are close enough! The only reason this is so, is because simultaneous measurements are not practical and may not be possible.
And yes for the purposes of testing the uncertainty principle sequential, not simultaneous, measurements can be good enough. But no matter how good the experiment and the data from it is, when the measurements are made sequentially, they are not as a matter of definition simultaneous.
Our whole discussion here has been explicitly in regards to the uncertainty principle:
It's only you who has insisted upon taking this discussion far and wide of its initial point. Every reference says that the uncertainty is inherent to the quantum system and that the precision with which one such property may be known is limited by the precision of the other. I've asked you several times to explain these and you've patently ignored them every time. These are not trivial but you seem to be intentionally dodging them.
This suggests to me that you either have not been reading or do not understand what you do read.
This is the post or close to the post, that seems to have set you off...
The rest of these are from almost every post I have made since, and I believe that I was making it clear that it is the practicality of simultaneous measurements of position and momentum in each...
The color emphasis was added to clarify intent.
Then remember this post of yours,
The next one was not a response to you but was on the issue.
From the above quotes I think it is clear what my contention was and what exactly I was asking you to prove up on. You continue to fail to present any link to an experiment that demonstrates simultaneous measurement of postion and momentum. And contrary to your last post, they demonstrate that all along I have been defending the practicality of a particular experiment.., to measure position and momentum, at the same time, and not the uncertainty principle itself.
That's a very long post only to continue to avoid what I've asked you numerous times:
Hell, you've even detoured into the completely off-topic relativistic mass in order to avoid addressing these. Let me know if you ever get over your serious cognitive bias.
The above is another deflection. Your were and continue to ask me to explain to you something I never questioned. And it was not the first question asked...
Your and the first first question(s) in bold:
My only reference to unmeasurable had been that portion, of my post, in bold. Since it seemed obvious that some methods of measurement leave a photon or electron unavailable for further measurement, I did not answer directly. I took your question as emotionally motivated... It seemed at the time you had not made any attempt to understand what I said and had put no real thought into your question.
Then later, I asked a question of you, and added my own interpretation. You did not offer your own interpretation in reply.
Then in the same post, I added.., not as a formal question,
And followed that in my next post with,
The question in context was the challenge for you to provide reference to an experiment where position and momentum were measured at the same time.
You failed to do so. Even your quotes from offsite sources suggested it is not possible, even in theory...
As far as my last long post is concerned, it is mostly made up of quotes from almost all of my posts that demonstrate, I had been talking about the practicality, of conducting an experiment that measures both position and momentum, at the same time. Which was a response to your assertion,
Which since in nearly every post I was speaking to the issue of practical simultaneous measurement of position and momentum, was a patently false assertion on your part.
This discussion is accomplishing nothing. I have made my point repeatedly. You continue to ignore and misrepresent intent. That really is a straw man argument. Early on you accused me of such and yet that is all you have put forward.., repeated misrepresentations.
This is going nowhere.
Yes, it was the initial issue, as you asserted that the uncertainty wasn't inherent to the phenomenon, but a measurement issue. If you are now saying that you agree with, i.e. "never questioned", every reference that states this is so then I'm satisfied with that.
I've been following this discussion, to some extent, but I've lost track.
Has anybody posted these links?
New 'Double Slit' Experiment Skirts Uncertainty Principle
The secret lives of photons revealed
Essentially, about a year ago a team from the University of Toronto used weak measurement techniques to simultaneously measure the (exact?) momentum and position of individual photons in a double slit experiment.
You are misrepresenting what I have said. (The straw man interpretation.) This was my initial statement;
There is nowhere in that statement that I even suggested that the uncertainty principle was not inherent to the particle. It does not make a difference whether an uncertainty is inherent (to the particle) or an artifact of measurement, it remains an issue of measurement. That initial statement in no way says anything about the origin of uncertainty. It only asserts that it is a measurement issue, which is in agreement with definition.
In that long post above, I referenced 21 posts where I included information indicating that I was referring to our inability to experimentally confirm the uncertainty principle, where both position and momentum are measured, at the same time. This was my only assertion in the last several pages of discussion. Burried in those same posts are several times that I explicitly said I was not questioning the uncertainty principle...
I did add the following philosophical comment, at the end of that initial post;
In hindsight this was a mistake. However, I had no way to know at the time you could not handle two concepts at once. It is unrelated to the uncertainty principle.
That said, the fact is when it comes to position and momentum, we do not have any practical means to test the uncertainty principle experimentally.., while measuring both, at the same time. This is not an attack on the UCP, it is a statement of fact, supported even by the references you have offered. And it is what I have been stating and restating now for several pages of posts.
To my knowledge, I have never questioned the uncertainty principle, itself. I am not a quantum physicist. I work hard enough just to get through the few papers in the area that are interest to me. In truth, even in challenging experimental proof of simultaneous measurements, I have only presented what I have seen in the literature, as described by those with far better credentials and authority that either of us.
Trippy, I do believe that Syne did link the first one. The following quote from that article seems to suggest that it is only statistically equivalent to a simutaneous measurement, rather than being actually simutaneous. I also could not find the original paper describing the experiment.
Steinberg's group sent photons one by one through a double slit by using a beam splitter and two lengths of fibre-optic cable. Then they used an electronic detector to measure the positions of photons at some distance away from the slits, and a calcite crystal in front of the detector to change the polarization of the photon, and allow them to make a very rough estimate of each photon's momentum from that change.
From the article it sounds like sequential measurements, that are statistically equivalent to what would be expected from simultaneous measurements. It is very hard to know what the experiment was actually, from the article.
I don't remember seeing the second one before, but it seems to be discussing the same experiment and specifically describes a weak measurement of momementum.
I think quite some time back I sarcastically described it as "good enough", rather than simultaneous.
All along my point has been that since position is a static measurement and momentum occurs over time, there is an inherent limitation to simutaneous measurement, of both. Position changes over time and momentum has no meaning apart from time and changing position.
None of this says anything about the UCP itself. There are many other experiments that support it. Simutaneous measurement is not necessary, for an experiment to produce accurate information and support or refute any principle.
Edit: Even the nature article referenced by the first link, A quantum take on certainty doesn't really completely describe the experiment. The momentum measurement is described at different times as a weak measurement, as acurately measured and as a rough estimate, perhaps depending on whether they are talking about single photons or averages from many photons.
Separate names with a comma.