There are two big statements that Tom makes often in his videos that seem to be controversial on the internet.
1. His explanation of quantum erasure, in which he states it doesn't matter if we measure the particles and erase the measurement data before looking at the result, or don't measure at all. A quantum measurement that is never looked at is as good as no measurement.
2. That in the double slit experiment the 'detectors' are acausal in the "collapse of the wave function" (a common misconception--that the detectors are somehow interfering with the particle and causing wave collapse). He uses the analogy that they one day decided to leave the detectors on, but just didn't record the data...and still got interference.
For item one, everyone is probably familiar with the slogans "interaction causes wave function collapse" or "you can't measure a particle without interacting with it". The former is false (or at least unproven), and the latter is obviously true. Thus, these statements are not equivalent and cannot be logically combined. In other words, you cannot combine them into one statment that if interaction happens, the wave function of a particle will collapse. The wave function collapsed, therefore interaction with the particle happened.
This is a formal logical fallacy
. This is just not true. There are many experiments, mostly of the delayed choice variety, that prove empirically that the time ordering of measurement events does not matter.
Measurement/interaction does not cause wave function collapse. If it did, these experiments would not work the way they do.
Item two has been somewhat more controversial, even garnering attention in a popular thread on a popular physics website.
Here I will pick some of the most cogent arguments from the thread and demonstrate how they are either wrong or misleading.
No. Once the data is detected by an irreversible process, deleting the data does not induce any changes. It does not matter whether you throw away the data or look at it. The only thing you can erase are reversible markers. For example you can make the paths in the double slit experiment distinguishable by using polarizers at each slit. Afterwards it is possible to change this polarization without destroying the photon, so you can shift the polarization of the beams originating from both slits such, that they are the same again. As no irreversible process happened, the interference pattern will reappear. In this case you could get which-way information and destroy the interference pattern if you measured the photon at the right position and time, but as you never measure, it persists. This is very different from actually measuring and throwing away the data, which will never give a persisting interference pattern.
He is talking here about the two slit quantum eraser.
This is in fact the very experiment Tom is talking about. Entangled pair is created, and one goes to Dp, other passes through slits to Ds. Standard setup produces interference due to the slits at Ds. Place QWP's(functional detectors) at each slit to measure polarization, and this marking causes which path info to be known and interference disappears. Now, perform a suitable polarization projection measurement on entangled particle going to Dp, and you can recover interference even leaving the QWP's in place. This person's entire argument hinges on the assumption that polarization is "reversible". That before the polarization measurement at Dp, no irreversible process happens. This is false
. Polarization and position ( and spin and momentum) are separate degrees of freedom of a quantum particle. The measurement of polarization does nothing actively to the position of any particle, especially if this measuement is separated in space with nothing physically connecting it to the particle. It simply provides a means by which to know which path a particle took (polarization X for path 1, polarization Y for path 2).
The apparatus is adjustible, and the experimenters placed Dp out in front of Ds, so that Ds registers a detection before Dp erases the information. Therefore, a so-called "irreversible" measurement does happen at Ds before Dp later erases the information. Registration at detector Ds, aka "irreversible physical interaction" did not
cause the wave function to collapse. Keep in mind that this is all conditional on the fact that nobody looks at Ds before erasing the information later at Dp: "In as much as our quantum eraser does not allow the experimenter to choose to observe which-path information or an interference pattern after the detection of photons (at Ds), it does allow for the detection of photon s before photon p, a situation to which we refer to as delayed erasure."
This fact is conveniently ignored and explained away in the context of coincidence counting. They go on to make the assertion that the decades of experiments and physicists doing them are only using a "trick" of coincidence counting, and so really there is nothing to contradict their beliefs, because we never actually see
the interference when information is erased in a delayed manner. Just ignore what the time stamps say. Beliefs preserved:
The information is not really obtained after detection of the first photon because all information is available only in coincidence counting, when both photons are already detected. What they do is more like a clever kind of filtering process than changing the past.
This is nonsense. Of course the information is not obtained after the physical detection of the first photon, because that measurement does not matter and does not collapse the wave function. It never happened because nobody ever looked at it. Then in coincidence the two measurements always correlate regardless of what order they happened. This is Tom's whole point.
I hope this simplified scheme shows, why the choice between the interference pattern and the which-way information can be done after the signal photon has already been detected, why it does not depend on whether we have a look at the data or not and that there are no problems with causality
None of this is fact. This ideology is of course at odds with experiment, and proven wrong long ago:
"It may be instructive to compare this proposal with other implementations of quantum eraser. In other implementations, one doesn’t get the interference directly and has to do a coincident counting of particles with certain states of the which-way detectors. Some people have this feeling, that the interference pattern is actually lost for good and one is only picking it out from the erased pattern in an artificial way. In this respect, this method has the advantage that one can observe the interference appear right before one’s eyes as the eraser magnet is switched on. Another point is that this method allows one to demonstrate quantum erasure using massive particles, instead of photons.
"Discussing the delayed-choice experiment, Wheeler concludes: “In this sense, we have a strange inversion of the normal order of time. We, now, by moving the mirror in or out have an unavoidable effect on what we have a right to say about the already past history of that photon” . We disagree with this interpretation. There is no inversion of the normal order of time – in our case we measure the photon before the ancilla deciding the experimental setup (open or closed interferometer). It is only after we interpret the photon data, by correlating them with the results of the ancilla, that either a particle- or wave-like behaviour emerges: behaviour is in the eye of the observer."
Well, it is very hard to find information about that guy. The only info I found is as follows: "Tom holds a Bachelor of Science in Physics and Math from Bethany College and a Master of Science in physics from Purdue University, as well as having done doctoral-level work at the University of Virginia. He is the physicist described as “TC” in Bob Monroe’s Far Journeys. Tom began researching altered states of consciousness with Bob in the early 1970s. He and Dennis Mennerich helped to design experiments and develop the technology for creating specific altered states. They were also the main subjects of Bob’s investigations at that time. For the past thirty years, Campbell has been focused on scientifically exploring the properties, boundaries, and abilities of consciousness. During that same time period, he excelled as a working scientist—a professional physicist dedicated to pushing back the frontiers of cutting-edge technology. Using his mastery of the out-of-body experience as a springboard, he dedicated his research to discovering the outer boundaries, inner workings, and causal dynamics of the larger reality system. In February of 2003, Tom published the My Big TOE trilogy. The acronym “TOE” is a standard term in the physics community that stands for “Theory Of Everything” and has been the Holy Grail of that community for fifty years. My Big TOE represents the results and conclusions of Tom’s personal and scientific exploration of the nature of existence. This overarching model of reality, mind, and consciousness merges physics with metaphysics, explains the paranormal as well as the normal, places spirituality within a scientific context, and provides direction for those wishing to personally experience an expanded awareness of All That Is."
He didn't look hard enough.
This sounds very much like crackpottery.
Read: He uses words we fear like "consciousness", therefore he is a crackpot.
However, he's almost certainly wrong if he's claiming conscious observation of the data caused the interference to disappear.
Tom does not claim this and never has.
Is this guy also selling crackpottery? It's another claim of a double slit experiment being done wherein the data is thrown out prior to backwall observation. (interference) ...The peer-reviewed references he cites (and also the one blandrew just cited) are all valid, but this guy's interpretation of what these mean is a clear case of crackpottery/
They are talking about the bottom layer website (reality as a simulation) that explains the delayed choice quantum eraser accurately.
It was even read and approved by Yoon Hoo Kim, one of the physicists who ran the experiment: "I do not think that there is anything wrong with your explanation." - Yoon-Ho Kim
You need spatially coherent light to form an interference pattern. The light in one arm of the entangled beams is not coherent enough for that.
No, you do not.
Interference is seen at Ds. This can be thought of in a physical manner as caused by two real waves interacting somehow (on path s1 and s2), correct? That is what is supposed to be causing interference. However, even when there is no photon emitted by NL2, there is still interference at Ds. So how does one photon traveling down path S1 still produce an interference pattern? Because there is no which-path information. The detector data alone (the only point in the experiment where there are measurements) cannot give information about the path of the photons. The paths are indistinguishable. So even though sometimes NL1 emitted a photon when NL2 didn't, there is still interference because when the measurement is made there is no way to know for sure the path that was taken. Thus interference is not caused by physical waves interacting, but "probability amplitudes adding". This is known as induced coherence without induced emission, where even the possibility that a photon could have come from another path from a separate source (even though it only went down one path) creates interference. One photon traveling one arm of an interferometer may produce a two-path interference pattern, if there are other paths that are indistinguishable from that path by looking at only the detectors.
This means that even if you did replace the beam-splitters BSA and BSB with mirrors, guaranteeing that the idlers would always be detected at D1 or D2 and that their which-path information would always be erased,
Talking about the delayed choice quantum eraser here. This is a blatant falsehood/misinterpretation. The purpose of the beamsplitters is to make paths to detectors indistinguishable (erase which path info). They are doing the same thing the polarization measurements do in the above two slit eraser (erasing info or not). It's just done in a different way. If there are mirrors in place of the beamsplitters, you then have created a distinguishability between paths (there is which path info).
It seems clear that these supposed "physics experts" have no clue what they are talking about, so i'll stop there. Tom is right and always has been. Debunked indeed. Feel free to repost this.