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THE CASE FOR THE ROLE OF CONSCIOUSNESS IN QUANTUM PHENOMENA

By Michael Betthauser

"It is the mark of an educated mind to be able to entertain a thought without accepting it." ~ Aristotle

With the advent and mathematical understanding of quantum mechanics humans have made incredible advancements in technology, medicine, and science. However there are some features of quantum mechanics that, although nobody disagrees with the math, the interpretation of the meanings of these features have been held in great controversy for nearly a century. I hope to show that it is the predominately held interpretation by the scientific community that an observer is a critical component to understanding the behavior of subatomic particles and that although a lot of work has been done to disprove this interpretation, no substantial evidence has come forth to falsify it. In fact, quite the opposite.

The Copenhagen Interpretation posits that the quantum wave function collapses when detected by an observer. The von Neumann-Wigner interpretation goes further to say that it is a conscious observer (and not merely a detecting apparatus) that's responsible for the collapse. When the Copenhagen Interpretation first came out in the 1920s most scientists could not accept the idea that the conscious observer has anything to do with "outside" physical systems. It has been a long held goal of scientists to be objective when doing research. These interpretations go directly against the notion of objectivity since, according to the interpretation, the very act of observing the physical system changes it. The Copenhagen Interpretation also includes the notion that One can never truly know what is happening at the two slits. In other words, One cannot know both the location and the velocity of a subatomic particle simultaneously, and that all One can ever know are the results seen, or observed, on the detector screen. According to the Copenhagen Interpretation this is not a limitation of the detecting equipment, but a limitation of Nature itself. This facet of the interpretation is called the Heisenberg Uncertainty Principle or otherwise referred to as wave/particle duality (see below). The principle states that the "location" of the particle acts like a wave, a spread out and vague thing of "probability" that does not become precisely known until One observes it. The act of observing the particle's location obscures the precise knowledge of the particle's velocity. While One observes the precise location, the velocity acts like a wave of probability, with no specific value, and vice versa. This paradox seemingly goes directly against the reductive materialism and the philosophies of Descartes and other deterministic thinkers that helped create the foundations of Science and the scientific method since the mere idea of probability is in direct opposition to determinism.

Ever since these initial interpretations determinist and materialist scientists around the world have been trying to find proof that would falsify them entirely. Even Wigner retracted his initial interpretation saying he was afraid it might lead to a type of solipsism. Einstein said "God does not play with dice," and much work has been put forth to disprove the Copenhagen Interpretation.

In order to compare the various differences between the Copenhagen Interpretation and other interpretations it's important to do so by outlining the major features of quantum mechanics.

Besides wave/particle duality, another facet of quantum mechanics is called entanglement. It's when two photons (or two electrons, or two protons, etc.) share a single state with each other, despite the amount of distance between them. It can be the state of any property, such as spin, excitement, velocity, or even location. When two photons are entangled, if the state of one photon is changed, the other photon will change it's state to correspond instantly. It's

Entanglement and non-locality in and of themselves have been largely ignored and left uninterpreted, although they play a major role in almost every interpretation and are used by quantum physicists regularly. I do know of one interpretation from the book, "The Tao of Physics" which suggests the Vedic scriptures were right when they said everything in the Universe is all just one interconnected thing. After all, even the Big Bang Theory suggests everything came from a "singularity." In Bohmian Mechanics (more on that below) it is said that all particles are entangled with each other, and in a sense, the entire Universe. This is called the Holographic Principle. More importantly to this topic though, entanglement and non-locality, despite their own implications, have been used by detractors of the Copenhagen Interpretation in various thought and real experiments in an effort to prove that it is indeed possible to know both the location and velocity of a particle simultaneously. In other words it was hoped that entanglement could disprove wave/particle duality and hence the notion of a probabilistic Universe. The idea is that since the entangled particles share a state, if the

One way to resolve the paradoxes and return to a deterministic view of reality is to take a completely different interpretation of the results. The Everett Interpretation, or Many Worlds Interpretation, postulates that instead of the particle acting like a wave, it is always acting like a particle with a deterministic path. It accounts for the particles seemingly statistical behavior by stating that all the possible statistical outcomes actually happen, and that events we don't perceive are actually taking place in another Universe. In other words, when the particle encounters the two slits, instead of behaving like a wave in order to pass through both slits simultaneously the entire Universe splits into two Universes, each an exact copy of the other except that in one Universe the particle went through one slit, and in the other Universe it went through the other slit. In this way, every single quantum possibility in the Universe, every electron that jumps orbital shells, every single quantum action everywhere throughout the Universe, causes the Universe to split into two Universes where each of the "possible" outcomes "actually" take place. This brings One to the notion that there must be an infinite number of Universes being infinitely created at near infinitely fast speeds in which to account for all possible quantum actions that are taking place. This interpretation is distasteful to a number of physicists (discussed in the video below) because the existence of other Universes in which the unobserved phenomenon is occurring cannot be experimentally confirmed and the interpretation does not account for why the observer seems to only be in one Universe but not the other.

The Many Worlds Interpretation, like other similar interpretations, relies largely on the concept of decoherence for it's experimental data. Decoherence has to do with superposition, the idea that two quantum states can exist simultaneously, similar to entanglement. In other words, a single particle can be spinning in two opposite directions, or be both excited or not excited simultaneously. The two opposing states of the particle are said to be "superimposed" on each other, or to have superposition. When the particle is observed by measurement the superposition vanishes and only one of the two states is seen. Which state that is seen is random due to INcoherence. In the process of creating superposition a beam of electromagnetic energy is "sent across" the particle. If this beam is set to a specific frequency it will cause the the superposition of the states to become COherent. Another way of looking at it is if an object's wave-like nature is split in two, then the two waves may coherently interfere with each other in such a way as to form a single state that is a superposition of the two states. This concept of superposition is famously represented by Schrödinger's cat, which is both dead and alive at the same time when it's in a coherent state inside a closed box. DEcoherence is the idea that once a particle in superposition interacts with the outside environment it loses superposition and coherence, which is said to "leak" into the environment. Materialists advocate this interpretation because the concept of the decoherence model is said to replace the collapse of the wave function and thus the observer. In this case its the environment that causes the "collapse." But this presents a problem: if a particle from the environment collapsed the particle in question, what collapsed that particle? And what collapsed the particle before it? This logically creates a chain of "collapsing measurements" that require a previous measurement to "collapse" the measuring device ad infinitum. This is referred to as the von Neumann Chain (see Measurement Problem below) . And although this may seem to remove the observer from the wave function collapse, it still does not explain why observation and measurement affect superposition, or entanglement, and thus does not actually disprove the Copenhagen Interpretation, but simply provides another explanation for some, but not all, of the quantum phenomenon. In fact, a recent research team found that for all practical purposes coherence and entanglement are two sides of the same coin. (See Quantum Decoherence below) The inability of the Many Worlds Interpretation or any other interpretations to account for the observer or measurement effect is referred to by physicists as the Measurement Problem (see below).

Now we examine Pilot Wave Theory which was used to develop The De Broglie-Bohm Theory otherwise known as Bohmian Mechanics. This theory also hopes to be deterministic and hopes to prove that a particle is always a particle, and that the wave is a real wave, with the two interacting together to create the observed quantum effects. In this case, the wave is a "pilot-wave" or "guiding wave" that carries the particle around. New evidence has been presented recently that shows a classical demonstration of several parts of this theory. In the demonstration a droplet of silicon oil is bounced on a vibrating silicon oil bath which then performs many behaviors previously only seen at the quantum level. The droplet is carried around by a pilot wave that is created by it's own bouncing and has replicated the double slit experiment in a way that is deterministic and classical (see video below). Although this is an impressive demonstration of the Pilot Wave Theory, there are a number of reasons that both Pilot Wave Theory and this experiment do not disprove the Copenhagen Interpretation.

Pilot Wave Theory assumes a new medium in which the pilot wave is waving. This medium is referred to as the sub-quantum medium and has yet to be experimentally detected. Although the MIT experiment used an oil bath as the medium for the droplet experiments this in no way gives any evidence for the medium that would need to exist at the quantum level. Many physicists compare this medium to the outdated idea of the "ether" that was thought to be the transmission medium for the propagation of electromagnetic or gravitational forces. Another notion was put forth that it is space-time itself that is waving, but that also has yet to be experimentally proven. Bohm himself said it is a new force called Quantum Force which is, incidentally, calculated using equations that were derived from Schrodinger’s equations that provide the wave function for quantum mechanics. In fact, the Quantum Force was purposefully designed by Bohm to give the same answers as quantum mechanics. In this sense his colleagues criticized him by saying his theory looked "rigged." (see Problem With Bohmian Mechanics below).

Pilot Wave Theory is also referred to as a "Hidden Variables" theory. This is because although it is a deterministic theory it must account for the apparent randomness (probabilistic nature) in quantum phenomena. It is said this randomness is due to the observers lack of knowledge about the starting variables in the particle's history. The theory states that if all the starting variables, such as location, velocity, etc., are known, then the precise outcome of the experiment can be determined (and not random). However, the theory also states that it is impossible to know the starting variables since that would require the knowledge of all the variables of the "system"

It's been demonstrated experimentally that you can't have a local, deterministic, real, theory. People intuitively expect all of those things to be true, but Bell's Inequality proves this isn't the case (see video under Pilot Wave Videos). The various interpretations all try to give up one of their "local", "real", or "definite" features in order to preserve the others, thus preserving at least a modicum of One's intuition. In the case of The De Broglie-Bohm Theory, deterministic values for the particle's location and velocity are gained at the cost of locality. In this theory, because every measured particle is intrinsically entangled with the surrounding environmental/experimental system, it is said to be non-locally connected. In other words, because the "hidden" starting variables are determined by the surrounding experimental setup and measuring system the particle "in question" and the "measuring" particle are said to be entangled, or non-locally connected. Since every system is a subsystem of a subsystem (etc.) of the whole Universe, this theory states that every single particle in the Universe is non-locally connected to every other particle. Yet another way of thinking about this is that every other particle IS every other particle. This non-local, or sometimes referred to as holographic property of the Universe has caused Bohm and other proponents of Bohmian Mechanics and Pilot Wave Theory to suggest there is a correlation between consciousness and matter since the brain is made of the very same entangled particles as the rest of the Universe (see Wikipedia article on Implicate/Explicate Order below).

It actually shouldn't be a surprise that a classical example of pilot waves replicating the double slit experiment has been found since the idea of Faraday Waves has been known since the 1800s. Bohmian Mechanics, for the most part, uses classical physics to describe the wave and particle so it stands to reason that a macroscopic version of that part of the theory should be found to be demonstrated in a classical way. The problem isn't whether pilot waves exist or even whether they can cause an oil droplet to exhibit certain quantum-like behaviors. Nobody is disagreeing with the math of Pilot Wave Theory or it's classical demonstrations. The problem is that it doesn't provide any new insights to what is actually happening at the quantum level. If the macroscopic oil droplet experiments were to prove every feature of Pilot Wave Theory (and quantum mechanics) they would have to demonstrate non-local entanglement, spin, and quite a few other features, which at this point doesn't seem experimentally possible.

"In its current, immature state, the pilot-wave formulation of quantum mechanics only describes simple interactions between matter and electromagnetic fields, according to David Wallace, a philosopher of physics at the University of Oxford in England, and cannot even capture the physics of an ordinary light bulb. 'It is not by itself capable of representing very much physics,' Wallace said. 'In my own view, this is the most severe problem for the [pilot wave] theory, though, to be fair, it remains an active research area.'" ~
Wired.com

Wheeler's Delayed Choice, Quantum Eraser, and the more recent Delayed Choice Quantum Eraser and other No-Loophole experiments have now completely confirmed beyond anyone's doubt that entanglement is a "real" phenomenon. At first this might seem like excellent news for The De Broglie-Bohm Theory since it so heavily relies upon the concept on non-locality. However, these experiments proved beyond any doubt the existence of wave/particle duality and the Heisenberg Uncertainty Principle. This is actually bad news for hidden variable theories since it proved that the wave function cannot be a physical thing (see It's A Bad Week For Hidden Variable Theories below). Also, it doesn't disprove the Copenhagen Interpretation since this interpretation also includes non-locality. In fact, for a lot of physicists, it reaffirms the role of the observer effect (see Quantum Eraser videos below).

A very common

The Quantum Eraser experiment is really just the Double Slit experiment with a twist. According to the Copenhagen Interpretation, when an observer looks to see "which way" the particle went, (which slit it went through) the wave function collapses, and we see no interference pattern, just the behavior of a particle. The Quantum Eraser experiments asked the question, "what will happen if we erase the 'which-way' information?" In other words, if we have a device that records which slit the particle went through (the "which-way information") but no one consciously observes it, and then we erase the which-way information before the particle reaches the detector plate, will we see an interference pattern? The quick answer by determinists and materialists is a resounding "no!" because it would seem that it was the device that collapsed the wave function when the which-path information was recorded. But this is a fallacy and goes against experimental evidence and I'll explain why.

To better explain the Quantum Eraser experiment let's continue to imagine that at the two slits we have a special machine that can record the which-way information. This is not exactly how they did the experiment but it's the logical equivalent and will help me get across some important ideas. This information is binary, and can be simply recorded as either a 1 if the particle went through one slit, and 0 if it went through the other. The particle is said to be "marked" or "tagged" with the which-way information because the 1 or 0 is only associated with this particle and no other. Now, the question is: if we erase the which-way information before the particle hits the detector plate which result will we see: The interference pattern or no interference pattern? If you believe that the machine (or the environment) collapsed the wave function when it recorded the which-way information, then it shouldn't matter what happens to the information after the particle passes the slits. If the wave function has collapsed then we should expect to see no interference pattern. However, that's not the case. Once the which-way information is erased, the particle

Wheeler's Delayed Choice Experiments were a series of thought experiments that finally led to real experiments carried out by Alaine Aspect et al. from 1987 to 2006. The Delayed Choice experiments also investigate wave/particle duality but ask a different question. According to the Heisenberg Uncertainty Principle, a particle is both a particle and a wave

In both of these setups a photon is emitted from the bottom left and goes through the first beam splitter (marked BS). In the first setup the two beams take their own path past the two detectors. However, in the second setup the paths are redirected by mirrors to a second beam splitter which

A common misconception about the Delayed Choice experiment comes from how the second beam splitter was introduced. Because a computer was used (human hands aren't fast enough) materialists argue that it was the computer that made the "decision" about the experimental setup, and not human consciousness. However this is fallacy since it makes no difference to the results if a human or a machine flips the switch. However, the computer did not

Now we finally come to the much hyped Delayed Choice Quantum Eraser experiment. Just as the name implies this experiment combines Wheeler's Delayed Choice experiment with the Quantum Eraser experiment to settle once and for all the debate on complimentarity. This experiment has the most misconceptions surrounding it, mostly due to it's complexity, so I will once again use a more simple, logically equivalent thought experiment to explain the results. To go back to the original Quantum Eraser experiment, imagine a machine that records the which-way information as a 1 or 0. Now imagine we separate the first beam splitter from the detectors by one light minute. This means it will take one minute before the result of interference or no interference is observed for each photon. After the photon has traveled through the first beam splitter the computer/machine records the which-way information then prints out either a solid white (1) or solid black (0) piece of paper which is perfectly concealed in a manilla envelope. The which-way information is erased from the computer memory so it is only contained in the manilla envelope and no conscious observer knows the which-way information. We only needed the light-minute to perform this operation and once the photon hits the detector a result is recorded as either a coincidence or no coincidence. If there is a coincidence it's a white piece of paper and vice versa. The result is also stored in a manilla envelope which is not consciously observed. The two envelopes are labeled "which-way" and "result," respectively, and are set side by side, thus "marking" or "tagging" them as being paired. Let's say we send several photons through the experiment in this way and two stacks of envelopes are collected. Now the experiment has ended and we have our information but none of it has been observed yet. This is the delayed choice part of the experiment because the choice to observe the which-way information has been delayed until after the entire experiment has been run! Now here's the interesting part. If we take the first pair of envelopes from the two stacks and

The original Delayed Choice Quantum Eraser experiment performed by Yoon-Ho Kim and Marlan O. Scully et al. in 1999 was not carried out with single photons, but rather entangled pairs of photons, and the results as I just described were carried out by correlating complete sets of data. Kim says in their released research paper, "The triggering of detectors D1 or D2 erases the which-path information so that either the absence of the interference or the restoration of the interference can be arranged via an

In the end, to summarize, the question of which interpretation is "correct" is that which is one of "completeness." Einstein and other determinist detractors of the Copenhagen Interpretation argue that since quantum mechanics cannot know precisely where the particle is at all times it

I hope I have shown that regardless of the interpretation One decides to adopt, each interpretation must still handle the role of the observer effect in one way or another. The inability to completely disprove the observer effect is called the Measurement Problem, and as it stands to date, no theory or interpretation has solved the Measurement Problem. This can only make sense, since how does One completely remove the observer from the experiment? It is the observer that asks the experimental question, the observer that sets up the experiment, and it is the observer that analyzes the results. And, according to quantum mechanics, when the observer asks Nature "What are you made of," Nature responds, "That depends on what you're asking," thus intrinsically linking consciousness to the behavior of quantum phenomena, as thus to the nature of matter itself.

"Quantum mechanics must be one of the most successful theories in science. Developed at the start of the twentieth century, it has been used to calculate with incredible precision how light and matter behave – how electrical currents pass through silicon transistors in computer circuits, say, or the shapes of molecules and how they absorb light. Much of today’s information technology relies on quantum theory, as do some aspects of chemical processing, molecular biology, the discovery of new materials, and much more." ~ BBC.com

Below you will find all the references you will ever need. After the videos are statements by Universities that show a bias towards the Copenhagen Interpretation. This includes a PDF from the Physics Department at UC Boulder that although it's goal is to encourage the teaching of more interpretations, it also shows that currently the Copenhagen Interpretation is the preferred interpretation.

MIT Graduate Student demonstrates actual double slit experiment using a laser.

Discovery Channel -Through The Wormhole - How Does the Universe Work.

Anton Zeilinger explains the observer effect with actual laser experiment.

The Fabric of the Cosmos: Quantum Leap - NOVA

Theoretical Physicist Brian Greene explains quantum mechanics

Explains observer effect at about

Explains quantum entanglement starting at

The Wonderful Weirdness of the Quantum World

David Z. Albert, Alan Alda, Brian Greene, Max Tegmark, William Phillips discuss the various interpretations, specifically the Copenhagen Interpretation vs. the Many Worlds Interpretation.

Discuss entanglement and observer effect at about

BBC: The Secrets Of Quantum Physics

Explains observer effect at about

Explains entanglement at about

Quantum Entanglement Lab - by Scientific American

SA editors George Musser and John Matson pay a visit to Professor Enrique Galvez of Colgate University, who has built a machine to observe quantum entanglement, the strange phenomenon that Einstein called "spooky action at a distance."

Explains act of measurement at

Non-locality explained at about

New York Times - Sorry, Einstein. Quantum Study Suggests ‘Spooky Action’ Is Real.

Nobel Peace Prize Awarded For Proof Of Entanglement

Coherent Light Explained

Quantum superposition of states and decoherence

A great explanation of decoherence.

Mentions measurement or observer effect at

Decoherence and consciousness - Max Tegmark

Mentions "something in the environment is learning" around

Physicists find quantum coherence and quantum entanglement are two sides of the same coin

The Measurement Problem

What constitutes as a measurement in quantum mechanics? Can it be completed with a measuring apparatus or does it extend further than that?

What Is A Measurement?

Although this video makes this assumption, One does not need to believe humans are the center of the Universe in order to explain Universal wavefunction collapse.

The Hard Problem discussed by physicist Tom Campbell

Adam Caulton, Assistant Professor at the Munich Center for Mathematical Philosophy

The Measurement Problem 1: Copenhagen and dynamical collapse theories

The Measurement Problem 2: Pilot Wave and Many Worlds theories

The pilot-wave dynamics of walking droplets

Yves Couder . Explains Wave/Particle Duality via Silicon Droplets [Through the Wormhole]

Bohmian Mechanics- An Alternative to Quantum

Explains why Bohmian Mechanics and Quantum Mechanics are indistinguishable at

Explains "weird results" at about

A problem with Bohmian Mechanics? Contextuality

'Contextuality' might mean that there are no alternatives to Quantum mechanics that are sensible. Given Quantum isn't sensible either, there may just not be any sensible theories at all.

Bell's theorem explained

Quantum Spin Explained

Alaine Aspect Public Lecture On His Delayed Choice Experiment

Professor Alain Aspect gave a public lecture at the Frederiksberg Gymnasium on the wave-particle duality for a single photon.

Delayed Choice Quantum Eraser Explained

Starts with a recap of the double slit experiment at

SKIP THE BEGINNING

DCQE explained starting at about

Quantum Eraser (This is different than the above experiment!)

Quantum Eraser Explained | Quantum Mechanics ep 5

This is an important example of the type of

Delayed Choice Quantum Eraser | Quantum Mechanics ep 6

Although the narrator is "disturbed" and "doesn't like the results" this experiment once again demonstrates the observer effect.

Physicist Thomas Campbell explains the Delayed Choice Quantum Eraser experiment with a logical equivalent.

Great explanation showing the way the data was correlated

Another excellent explanation of the Delayed Choice and Eraser experiments.

Delayed Choice Quantum Eraser Research Paper

Yoon-Ho Kim, Rong Yu, Sergei P. Kulik, Yanhua Shih, and Marlan O. Scully Phys. Rev. Lett. 84, 1 – Published 3 January 2000

Delayed-choice gedanken experiments and their realizations

"The formation of the interference pattern requires the existence of two slits, but how can a single photon passing through one slit `know' about the existence of the other slit? We are stuck going back to thinking of each photon as a wave that hits both slits. Or we have to think of the photon as splitting and going through each slit separately (but how does the photon know a pair of slits is coming?). The only solution is to give up the idea of a photon or an electron having location. The location of a subatomic particle is not defined until it is observed (such as striking a screen)."

"Evidently, when we look at what is going on at the slits we cause a qualitative and irreversible change in the behavior of the electrons. This is usually called the 'Heisenberg Uncertainty Principle.'"

"These characteristics lead to the belief that an observer interacts with a system under study to such an extent that the system cannot be thought of as having an independent existance. This goes contrary to one of classical physics key postulates (unproven assumptions) that the universe exists independent of an observer."

"Heisenberg's principle stressed again the recurrent motif of the scientist's active role in creating the observed reality. It implied that we cannot observe the world without influencing its course."

Introduction to Quantum Mechanics and Consciousness

In an effort to promote more awareness for other interpretations, UC Boulder conducted this survery and found that the Copenhagen Interpretation or "Quantum" interpretation was the one favored by students.

During most of the 20th century, collapse theories were clearly the mainstream view, and the question of "interpretation" of quantum mechanics mostly revolved around how to interpret "collapse". Proponents of either "pilot-wave" (de Broglie-Bohm-like) or "many-worlds" (Everettian) interpretations tend to emphasize how their respective camps were intellectually marginalized throughout 1950s to 1980s. In this sense, all non-collapse theories are (historically) "minority" interpretations.

However, since the 1990s, there has been a resurgence of interest in non-collapse theories. The Stanford Encyclopedia as of 2015 groups interpretations of quantum mechanics into "Bohmian mechanics" (pilot-wave theories),[11] "collapse theories",[12] "many-worlds interpretations",[13] "modal interpretation"[14] and "relational interpretations"[15] as classes of into which most suggestions may be grouped.

As a rough guide development of the mainstream view during the 1990s to 2000s, consider the "snapshot" of opinions collected in a poll by Schlosshauer et al. at the 2011 "Quantum Physics and the Nature of Reality" conference of July 2011.[16] The authors reference a similarly informal poll carried out by Max Tegmark at the "Fundamental Problems in Quantum Theory" conference in August 1997.

The Copenhagen interpretation is an expression of the meaning of quantum mechanics that was largely devised in the years 1925 to 1927 by Niels Bohr and Werner Heisenberg.

Those who hold to the Copenhagen interpretation are willing to say that a wave function involves the various probabilities that a given event will proceed to certain different outcomes. But when the apparatus registers one of those outcomes, no probabilities or superposition of the others linger.[20]

According to Howard, wave function collapse is not mentioned in the writings of Bohr.[3]

Some argue that the concept of the collapse of a "real" wave function was introduced by Heisenberg and later developed by John von Neumann in 1932.[21] However,

In 1952 David Bohm developed decoherence, an explanatory mechanism for the appearance of wave function collapse. Bohm applied decoherence to Louis DeBroglie's pilot wave theory, producing Bohmian mechanics,[23][24] the first successful hidden variables interpretation of quantum mechanics. Decoherence was then used by Hugh Everett in 1957 to form the core of his many-worlds interpretation.[25] However decoherence was largely[26] ignored until the 1980s.[27][28]

The von Neumann–Wigner interpretation, also described as "consciousness causes collapse [of the wave function]", is an interpretation of quantum mechanics in which

Objections to the interpretation

There are other

To many scientists this interpretation fails to compete with other interpretations of quantum mechanics because "consciousness causes collapse" relies upon an

THE BORN RULE

Many-worlds implies that all possible alternate histories and futures are real, each representing an actual "world" (or "universe"). In lay terms, the hypothesis states there is a very large-perhaps infinite[2]-number of universes, and everything that could possibly have happened in our past, but did not, has occurred in the past of some other universe or universes.

A consequence of removing wavefunction collapse from the quantum formalism is that the Born rule requires derivation, since many-worlds derives its interpretation from the formalism. Attempts have been made, by many-world advocates and others, over the years to derive the Born rule, rather than just conventionally assume it, so as to reproduce all the required statistical behaviour associated with quantum mechanics.

However, in 1985, David Deutsch published three related thought experiments which could test the theory vs the Copenhagen interpretation.[54] The experiments require macroscopic quantum state preparation and quantum erasure by a

Objective collapse theories differ from the Copenhagen interpretation in regarding both the wavefunction and the process of collapse as ontologically objective. In objective theories, collapse occurs randomly ("spontaneous localization"), or when some physical threshold is reached, with observers having no special role. Thus, they are realistic, indeterministic, no-hidden-variables theories.

GRW collapse theories have unique problems.

The original QMSL models had the drawback that they did not allow dealing with systems with several identical particles, as they did not respect the symmetries or antisymmetries involved. This problem was addressed by a revision of the original GRW proposal known as CSL (continuous spontaneous localization) developed by Ghirardi, Pearle, and Rimini in 1990.[2]

Decoherence represents a challenge for the practical realization of quantum computers, since such machines are expected to rely heavily on the undisturbed evolution of quantum coherences. Simply put, they require that coherent states be preserved and that decoherence is managed, in order to actually perform quantum computation.

The quantum eraser experiment described in this article is a variation of Thomas Young's classic double-slit experiment. It establishes that when action is taken to determine which slit a photon has passed through, the photon cannot interfere with itself. When a stream of photons is marked in this way, then the interference fringes characteristic of the Young experiment will not be seen. The experiment described in this article is capable of creating situations in which a photon that has been "marked" to reveal through which slit it has passed can later be "unmarked."

The experiment was designed to investigate peculiar consequences of the well-known double slit experiment in quantum mechanics as well as the consequences of

The delayed choice quantum eraser experiment

This result is similar to that of the double-slit experiment since interference is observed when it is not known which slit the photon went through, while no interference is observed when the path is known.

However, what makes this experiment possibly astonishing is that, unlike in the classic double-slit experiment, the choice of whether to preserve or erase the which-path information of the idler was not made until

PILOT WAVE THEORY

PRINCIPLE OF LOCALITY

THE IMPLICATE AND EXPLICATE ORDER

FARADAY WAVES

De Broglie–Bohm theory gives the same results as quantum mechanics. It treats the wavefunction as a fundamental object in the theory as the wavefunction describes how the particles move.

De Broglie–Bohm theory is often referred to as a "hidden variable" theory

The Bohm interpretation preserves realism, hence it needs to violate the principle of locality in order to achieve the required correlations . It does so by maintaining that both the position and momentum of a particle are determinate in that they correspond to the definite trajectory of the particle;

The recurrence and stability of our own memory as a relatively independent sub-totality is thus brought about as part of the very same process that sustains the recurrence and stability in the manifest order of matter in general.

are several equivalent mathematical formulations of the theory and it is known by a number of different names.

Faraday waves, also known as Faraday ripples, named after Michael Faraday, are nonlinear standing waves that appear on liquids enclosed by a vibrating receptacle. When the vibration frequency exceeds a critical value, the flat hydrostatic surface becomes unstable. This is known as the Faraday instability. Faraday first described them in an appendix to an article in the Philosophical Transactions of the Royal Society of London in 1831.[1][2]

Bohm's original aim was not to make a serious counterproposal but simply to demonstrate that hidden-variable theories are indeed possible.[24] (It thus provided a supposed counterexample to the famous proof by John von Neumann that was generally believed to demonstrate that no deterministic theory reproducing the statistical predictions of quantum mechanics is possible.)