Category Archives: neither AND nor OR

EPR paradox, 11.3

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Black hole information paradox, 2.2.3

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It shouldn’t be so surprising that unitarity survives completely while causality doesn’t. After all, the basic postulates of quantum mechanics, including unitarity, the probabilistic interpretation of the amplitudes, and the linearity of the operators representing observables, seem to be universally necessary to describe physics of any system that agrees with the basic insights of the quantum revolution.

On the other hand, geometry has been downgraded into an effective, approximate, emergent aspect of reality. The metric tensor is just one among many fields in our effective field theories including gravity.

— Black hole information puzzle

— Lubos Motl

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identical particles

~ some particles are identical, except having different positions

~ some particle trajectories are indistinguishable

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trajectory indistinguishability

~ particle identity is an approximate concept

~ causality is an approximation

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spacetime is defined by causality

~ so spacetime is also an approximation

— Me@2022-02-11 12:47:14 AM

— Me@2022-02-13 03:38:35 PM

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2022.02.13 Sunday (c) All rights reserved by ACHK

EPR paradox, 11.2

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Black hole information paradox, 2.2.2

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physical definition

~ define the microscopic events in terms of observable physical phenomena such as the change of readings of the measuring device

~ define unobservable events in terms of observable events

— Me@2022-01-31 08:33:01 AM

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superposition

~ lack of the existence of measuring device to provide the physical definitions for the (difference between) microscopic events

— Me@2022-01-31 08:33:01 AM

— Me@2022-02-12 10:22:09 AM

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In the EPR experiment, how come the two always correlate if there are no definite states before the measurements?

When you actually know the results of your experiment, it does affect your expectations of the faraway results if there are correlations – and correlations are almost always there iff the two subsystems have interacted or been in contact in the past). — Lubos Motl

Microscopically, there is no time, in the sense that all the (past and future) quantum states have one-one correspondences. All results are deterministic. No causality violation required nor allowed. — Me@2016-10-14 07:55:48 PM

This is called quantum determinism, which may or may not be correct. But quantum determinism, even if true, is not necessary for explaining the EPR experiment, if we understand that:

1. Superposition is mathematical, not physical.

2. “Wave function collapse” is mathematical, not physical. It just means that we have to replace the wave function with another if we replace the system with another.

The system before and after the detectors activated should be regarded as two distinct systems. In other words, when you activate the detectors, you have actually replaced a system-without-detectors with a system-with-detectors.

“Wave function collapse” replaces the pure state wave function with a mixed state wave function. In other words, it replaces the pure state of superposition with a mixed state of eigenstates. In other other words, it replaces quantum probability with classical probability.

Before opening the box, the cat is not in a superposition state. Instead, it is in a mixed state.

The uncertainty is classical probability, which is due to lack of detailed knowledge, not quantum probability, which is due to lack of definition (in terms of physical phenomena difference).

— Me@2022-01-29 10:38:19 PM

— Me@2022-02-12 10:28:57 AM

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2022.02.12 Saturday (c) All rights reserved by ACHK

EPR paradox, 11.1

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Black hole information paradox, 2.2.1

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superposition

~ lack of the existence of measuring device in the definition of the experimental setup to define the difference between microscopic events in terms of the difference between observable physical events

— Me@2022-01-31 08:33:01 AM

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Note that superposition is mathematical, not physical. A wave function is not probabilities, nor a physical wave. Superposition applies only to wave functions, not to probabilities, nor to physical realities.

If superposition had been of probabilities or of physical realities, there would have been no interference patterns in the double-slit experiment.

— Me@2022-02-11 03:32:47 PM

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For example, in the double-slit experiment, if no detector is installed, the system is in a quantum superposition state.

It is not that each individual photon is in a superposition, because an individual particle has no 100% objective identity, due to the indistinguishability of identical particles. Instead, it is that the system of the whole experimental setup is in a superposition.

This applies also to other more complicated experimental setups, such the EPR experiment, the delayed-choice experiment, the delayed-choice quantum eraser, etc.

— Me@2021-01-23 12:57 AM

— Me@2022-02-11 03:29 PM

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physical definition

~ define the microscopic events in terms of observable physical phenomena such as the change of readings of the measuring device

~ define unobservable events in terms of observable events

— Me@2022-01-31 08:33:01 AM

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a definite state

~ an eigenstate

~ a state that has given a physical definition

— Me@2022-02-11 01:19:57 PM

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What we do in the present does not change the past, but changes we can see/say about the past. — Wheeler on Delayed choice quantum eraser, paraphrased, Me@2018-02-04 03:40:27 PM

Physics is not about reality, but about what one can say about reality. — Bohr, paraphrased

Physics should deduce what an observer would observe, not what it really is, for that would be impossible. — Me@2018-02-02 12:15:38 AM

It is because, tautologically, any state that cannot be physically defined is logically and physically meaningless.

In other words, any state that has no distinguishing observable effects does not make sense. For example, if in a double-slit experiment, no detector is allowed, then it is no point to label the state either as “go-left” or as “go-right”. Instead, we have to label the state as a superposition state.

Some unobservable (aka microscopic) variables are meaningless. It is not because of any philosophical points of view, but because we have not defined those variables in terms of observables or observable events, aka physical phenomena. In other words, those variables have no physical definitions yet.

— Me@2022-02-11 03:50:59 PM

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Quantum mechanics, and physics in general, gives the rules of storytelling about reality. A story is a post hoc description of a physical event. In other words, quantum mechanics, and physics in general, is about phenomena, not noumena.

phenomenon (plural phenomena)

~ thing appearing to view

~ reality with respect to an observer

noumenon (plural noumena)

~ thing-in-itself

~ reality independent of any observers

— Me@2022-02-11 3:00 PM

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2022.02.11 Friday (c) All rights reserved by ACHK

The superposition language

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classical language

~ all particles are distinguishable

~ every particle has an objective identity

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quantum language

~ some particles are identical

~ some particles are indistinguishable

~ Not every particle has an objective identity

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[guess]

When you insist on using all-particles-are-distinguishable language on the maybe-indistinguishable particles, you get the superposition language.

[guess]

— Me@2022-02-05 09:26:26 PM

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2022.02.10 Thursday (c) All rights reserved by ACHK

Photon dynamics in the double-slit experiment, 6.2

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A wave function is used for calculating probability, but itself is not a probability.

However, like probability, a wave function is not a physical wave, which is located in physical space-time.

Like probability, a wave function is a mathematical tool that exists only in the conceptual space.

So, like probability, a wave function cannot be measured by any device.

— Me@2022-02-02 6:48 AM

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2022.02.09 Wednesday (c) All rights reserved by ACHK

Photon dynamics in the double-slit experiment, 6

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Why don’t we see superposition states for macroscopic objects?

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A superposition state is not any “overlapping” of multiple physical states.

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A superposition state is a wave function, which is not a physical wave located in physical space.

Instead, it is a mathematical tool to calculate probability distributions.

— Me@2022-02-01

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EM waves are not photon wave functions because EM waves are physical, while wave functions are mathematical.

— Me@2022-02-01

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In addition, the electromagnetic fields are observable (e.g. with an oscilloscope) while Schroedinger wave functions are not observable, even in principle. Clearly, then, the fields are not wavefunctions, are physical, observable fields, rather than merely what you take the modulus-square of to obtain the probability of finding a photon somewhere. The existence of some “wavefunction of the photon” is not a fully settled issue.

— Wikipedia on Photon dynamics in the double-slit experiment

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2022.02.06 Sunday (c) All rights reserved by ACHK

Square root of probability, 3.2.3

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Eigenstates 3.3.2.3

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2.2

Decoherence is not a physical process.

Instead, it is a logical process of replacing one physical system (an experimental setup design) with another.

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Sometimes, it seems to be a physical process when we perform physical operations based on its logic. For example, when we want to execute our plan of replacing a physical system with another one which is identical but with detectors activated.

We do not really need to create another physical system to achieve that. We just have to switch on the not-yet-activated detectors already installed in the original experimental setup. The effect is identical to replacing the original.

— Me@2022-02-04 08:27:23 PM

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But for simplicity, we use the common quantum mechanics language for the time being:

The system has already decohered long before the radioactive trigger’s effect has reached the cat. Since radioactive atom touched the environment, the quantum state of the system has decohered.

Better language:

The behaviour of any macroscopic (aka observable) objects, before cat in the operation chain, has already provided the physical definitions of whether the atom has decayed and not.

— Me@2022-02-04 11:23:49 PM

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Before opening the box, the cat is not in a superposition state. Instead, it is in a mixed state.

The uncertainty is classical probability, which is due to lack of detailed knowledge, not quantum probability, which is due to lack of definition (in terms of physical phenomena difference).

— Me@2022-01-29 10:38:19 PM

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Most people will accept quantum mechanics once they realize that it follows the classical logic.

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Wrong:

1.  go-left   

2.  not-go-left   

3.  both go-left and not-go-left

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Correct but misleading:

1.  go-left   

2.  not-go-left   

3.  “go-left” and “not-go-left” are meaningless

because they are

not defined by physical observable events;

in other words, not defined in terms of physical phenomena yet

That is still misleading because it acts as if we have to use 3-valued logic.

But actually, 3-valued logic is not needed at all. 3-valued logic will appear only if we insist on using the one-layer presentation to represent the actually two-layered logic structure. It is actually binary logic all along:

1.  “go-left” and “not-go-left” are defined

“Going-left” and “not-going-left” are physically distinguishable, because detectors are allowed in the experimental setup.

1.1  go left

1.2  not go left

2.  “go left” and “not go left” are undefined

“Going-left” and “not-going-left” are physically indistinguishable, because detectors of any kind are not allowed in the experimental setup definition; so “going-left” and “non-going-left” are logically meaningless.

On any layer, there are only 2 cases:

For any proposition A, either A is true or \text{NOT}~A is true, but not both.

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Most people will accept quantum mechanics once they realize that, in a sense, it actually creates the classical logic by making the world consistent.

— Me@2022-01-12 12:40:12 PM

— Me@2022-01-29 04:03:53 PM

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2022.02.05 Saturday (c) All rights reserved by ACHK

Square root of probability, 3.2.2

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Eigenstates 3.3.2.2

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Actually, quantum mechanics does NOT allow any violation of these logical laws. A quantum superposition state is NOT any “overlapping” of multiple physical states. A quantum superposition state is ONE single physical state.

Contrary to popular belief, Schrödinger created the thought experiment to illustrate that a quantum superposition state should NOT be regarded as any “overlapping” of multiple physical states.

To explain that, we should use the most basic quantum experiment, the double-slit experiment, instead of the cat experiment, because:

1.

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And more fundamentally:

2.1

The cat-alive state is a well-defined state. The cat-dead state also.

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A quantum state must be a superposition state when in (the definition of) the experiment setup, some definitions of trajectories are missing.

The “definitions” here must be in terms of physical phenomena, because “trajectories” have no objective existence, due to the fact that fundamentally particles have no objective identities; fundamentally, identical particles are indistinguishable.

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“Which trajectory has a particle travelled along” is a hindsight story.

“The electron at location x_1 at time t_1 and the electron at location x_2 at a later time t_2 are actually the same particle” is also a hindsight story.

These kinds of post hoc stories do not exist when some definitions of trajectories are missing in the overall definition of the experiment setup. In such a case, we can only use a superposition state to describe the state of the physical system.

Since such a situation has never happened in a classical (or macroscopic) system, it gives a probability distribution that has never existed before. Such a new kind of probability distribution can only be deduced by the mathematical representation of a superposition state. In other words, such a new kind of probability distribution is encoded in and only in the mathematical language of superposition state.

For example, in the double-slit experiment, if the experiment setup definition disallows any kinds of detectors (that can distinguish particle-go-left and particle-go-right), then tautologically, “go-left” and “go-right” are logically indistinguishable; “go-left” itself and “go-right” itself are both physically meaningless. So the system is actually in ONE single state, namely the superposition state.

Since “go-left” and “go-right” both have no physical meanings, “it is in a superposition state of going-left state and going-right state” means neither “the particle goes left and goes right” nor “the particle goes left or goes right“. Instead, it means that

2.11   going-left and going-right are logically indistinguishable so the system is actually logically ONE single physical state;

2.121   the probability distribution is not that of going-left nor that of going-right;

2.122   so this new kind of state requires a never-seen-before probability distribution,

2.123   which can be calculated from the mathematical expression of the superposition state, aka the wave function.

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Indeterminacy in measurement was not an innovation of quantum mechanics, since it had been established early on by experimentalists that errors in measurement may lead to indeterminate outcomes. However, by the later half of the eighteenth century, measurement errors were well understood and it was known that they could either be reduced by better equipment or accounted for by statistical error models. In quantum mechanics, however, indeterminacy is of a much more fundamental nature, having nothing to do with errors or disturbance.

— Wikipedia on Quantum indeterminacy

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Quantum indeterminacy is not due to physical limitations. Quantum indeterminacy is a definitional indeterminacy–some necessary definitions are not precise enough or even missing altogether.

It occurs when you do not allow installing any measuring devices (for some variables) in the experiment. It occurs when you define an experiment in such a way that you cannot define, for example, the difference between trajectories based on the difference between possible physical phenomena.

However, since the difference between the cat-alive state and cat-dead state is well-defined, there is no indeterminacy-due-to-undefined-difference (aka quantum indeterminacy). So there is no so-called “quantum superposition of cat-alive and cat-dead“. In other words, the cat itself is already a measuring device for the particle state.

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For simplicity, assuming that in the box, there were no measuring devices. So before putting the cat there, the atom was in a superposition of decayed and not-decayed-yet.

That does not mean that the atom is physically in two states at the same time. Instead, it actually means that there is logically no difference between decayed and not-yet-decayed, because there is no existence of a measuring device that can make the definitional physical difference.

superposition

~ lack of the existence of measuring device in the definition of the experimental setup to define the difference between microscopic events in terms of the difference between observable physical events

physical definition

~ define the microscopic events in terms of observable physical phenomena such as the change of readings of the measuring device

~ define unobservable events in terms of observable events

However, while you are designing the experiment, once you allow the cat to be inside, you have actually provided a physical definition of “the atom has decayed” and “the atom has not decayed yet“. The cat is actually the measuring device whose existence provides that physical definition. That is the so-called “wave function collapse”.

The “wave function collapse” itself is not a physical process. It is actually a change of probability distribution due to the change of experimental design. The experiment with measurement device and that without measurement device are actually two distinct experiments with distinct probability distributions.

wave function collapse

~ probability distribution change (replacement) due to replacing “the experiment without measurement device” with “the experiment with measuring device“

2.2

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— Me@2022-01-31 08:33:01 AM

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Although the final device in the chain of measurement needs to be macroscopic for a human being to read, the “measuring device” does not have to be macroscopic.

It even can be only one particle, as long as it can store the result of “going left” or “going right”.

In other words, if by adding an object in the experiment during the experiment design process, “go left” and “go right” acquire their physical definitions (physical meanings) by being distinguishable, then that object is a “measuring device”.

measuring device

~ logical case differentiator during the experiment design process

~ physical case differentiator during the experiment

— Me@2022-02-01 11:02:20 AM

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2022.02.01 Tuesday (c) All rights reserved by ACHK

The square root of the probability, 3.2.1

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Eigenstates 3.3.2.1

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According to Schrödinger, the Copenhagen interpretation implies that the cat remains both alive and dead until the state has been observed. Schrödinger did not wish to promote the idea of dead-and-live cats as a serious possibility; on the contrary, he intended the example to illustrate the absurdity of the existing view of quantum mechanics.

— Wikipedia on Schrödinger’s cat

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Quantum mechanics seems to be unacceptable not because it is strange. Any new science must be strange because it must contain something never known and never expected before.

Quantum mechanics seems to be unacceptable not because it is strange, but because common quantum mechanics education, especially popular science, is so misleading that it makes quantum mechanics look bad; people falsely believe that quantum mechanics violates some of Aristotle’s 3 laws of logic:

1. Law of identity

2. Law of non-contradiction

3. Law of excluded middle

These 3 laws basically mean that

For any proposition A, either A is true or \text{NOT}~A is true, but not both.

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Actually, quantum mechanics does NOT allow any violation of these logical laws. A quantum superposition state is NOT any “overlapping” of multiple physical states. A quantum superposition state is ONE single physical state.

Contrary to popular belief, Schrödinger created the thought experiment to illustrate that a quantum superposition state should NOT be regarded as any “overlapping” of multiple physical states.

To explain that, we should use the most basic quantum experiment, the double-slit experiment, instead of the cat experiment, because:

1.

Although we can regard the cat itself as a system of fundamental particles, we should not do so in this case. Instead, we should just regard the cat itself as one classical object (system).

If we regard the cat itself as a system of fundamental particles, the superposition quantum state will need to include also the classically-makes-NO-sense particle configurations as component eigenstates. In other words, besides the cat-alive state and cat-dead state, the superposition quantum state will need to also include, for example:

1.1   the state of “the cat transforms into a dog”;

1.2   the state of “the cat disappears”;

1.3   the state of “half of the cat becomes a computer and half becomes a harddisk”;

1.4   etc.

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The major fault of the many-worlds interpretation of quantum mechanics is that it includes only the eigenstates (worlds) that make common sense.

2.1

…

2.2

…

— Me@2022-01-30 04:21:17 PM

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2022.01.30 Sunday (c) All rights reserved by ACHK

Particle indistinguishability is the major source of quantum effects, 1.05

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If there is no particle indistinguishability, every particle has a well-defined identity, then every particle has a well-defined trajectory.

Then even if no detector is installed, there is a well-defined difference between go-left and go-right in the double-slit experiment.

Then there will be no indistinguishability of cases, aka quantum superposition states.

— Me@2021-02-04 7:04 AM

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2021.03.22 Monday (c) All rights reserved by ACHK

Trajectory

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It is not possible to derive Schrödinger’s equation from “anything we know”.

— R. P. Feynman

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The most confusing part in the Quantum Mechanics is [the concept of] Trajectory.

There exist[s] no fixed path for a particle to go from Point A to Point B. This is clearly visible from [the] Interference Experiment.

So, the approach here is to work with deductive reasoning. We eliminate the possible region/paths which [are] impossible to be followed.

To do this we assume that Energy Conservation Relation is valid for Quantum Mechanics too. So, those regions where particle[s] [violate] this law automatically [get] eliminated.

Then, we guess [the] State Function[s] for certain conditions i.e. how it should be in certain cases, then build an energy conservation equation with that. We will shortly demonstrate how Schrodinger itself reached the conclusion.

— Why can’t the Schrödinger equation be derived?

— Abhas Kumar Sinha

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2021.02.28 Sunday ACHK

Particle indistinguishability is the major source of quantum effects, 1.2

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However, this definition of “every trajectory is well-defined” has a problem.

If the trajectory concept cannot predict correct experiment results, “the trajectory concept is broken” is only one of the possible causes.

In other words, how can you know the non-classical results (aka quantum effects) are not due to other factors?

— Me@2021-02-15 05:03:20 PM

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This question is exactly what the Bell tests designed for.

No. It is not correct. A Bell test can check whether the trajectory concept is well-defined, but not whether “the trajectory concept is broken” is the major source of quantum randomness.

However, it is the undefinable trajectory concept that makes the superposition, which is a unique and major feature of quantum mechanics.

— Me@2021-02-07 06:03:53 PM

— Me@2021-02-15 10:24:17 PM

— Me@2021-02-21 05:14:55 PM

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To date, all Bell tests have found that the hypothesis of local hidden variables is inconsistent with the way that physical systems behave.

— Wikipedia on Bell test

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Source of quantumness

~ the indistinguishability of cases

~ the individual trajectory of individual particles cannot be well-defined

~ the indistinguishability of particles

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~ “individual” particle has no individuality

~ “individual” particle has no individual identity

— Me@2021-02-06 4:03 PM

— Me@2021-02-15 9:14 PM

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2021.02.21 Sunday (c) All rights reserved by ACHK

Particle indistinguishability is the major source of quantum effects, 1.1

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If particles are distinguishable, there is no quantum-ness.

Why?

— Me@2021-02-06 4:00 PM

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If there is no particle indistinguishability, all trajectories are distinguishable, then there is no case indistinguishability.

In other words, if every trajectory is well-defined, there is no indistinguishability of cases, even when no detector is installed.

Why?

— Me@2021-02-06 4:01 PM

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In other words, how to define “every trajectory is well-defined” when no detector is installed?

— Me@2021-02-15 5:00 PM

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Thought experiment:

In the double-slit experiment, turn on the detector. Then observe the pattern on the final screen.

Next, tune down the detector’s accuracy/resolution a little bit. Repeat the experiment. Observing the pattern again.

Keep repeating the experiment with a little bit lower detector accuracy/resolution at each iteration.

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If a non-classical pattern never appears on the final screen, we can say that each trajectory is well-defined.

In other words, if the trajectory concept can predict correct experiment results, we say that the trajectory concept is well-defined.

— Me@2021-02-06 4:02 PM

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It is because the final screen itself is a kind of detector, although not a position detector.

— Me@2021-02-06 05:07:21 PM

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So it is a kind of Bell-type experiment.

— Me@2021-02-07 06:03:53 PM

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However, this definition of “every trajectory is well-defined” has a problem.

If the trajectory concept cannot predict correct experiment results, “the trajectory concept is broken” is only one of the possible causes.

In other words, how can you know the non-classical results (aka quantum effects) are not due to other factors?

— Me@2021-02-15 05:03:20 PM

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2021.02.15 Monday (c) All rights reserved by ACHK

Quantum information makes classical information consistent, 1.2

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Consistent histories, 10.2 | Cosmic computer, 2.2

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Quantum mechanics is a theory of classical information.

— Me@2021-02-03 07:48:01 AM

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Quantum mechanics is a theory of measurement results.

Quantum mechanics explains why measurement results are always consistent with each other.

— Me@2021-02-11 11:10:17 AM

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2021.02.11 Thursday (c) All rights reserved by ACHK

Quantum information makes classical information consistent

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Consistent histories, 10 | Cosmic computer, 2

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Wrong: Quantum information is inconsistent and classical information is consistent.

Source: Misunderstanding quantum superposition; regarding mathematical superposition as physical superposition, violating logic, such as a particle has gone through both the left slit and right slit at the same time.

Right: Quantum information is what makes sure that classical information is consistent even when there are indistinguishabilities of some classical cases.

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a quantum superposition state

~ a state without classical equivalence because some classical cases are indistinguishable-even-in-principle that they are logically forced into one SINGLE physical state

— Me@2021-02-03 01:46:43 PM

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quantum superposition

= mathematical superposition

= physical NON-superposition

= logically one SINGLE physical state

= go-left and go-right are logically indistinguishable due to the “experiment setup is without detector” part of the definition

= the SINGLE state of “both slits are open but no measuring device is installed; so for each photon, we have no which-way information; because there is no which-way DEFINITION”

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The definition requirement means that you have to answer

Under what physical phenomenon/phenomena occur(s) that you will say that the photon has gone through the left slit?

In other words, you need to DEFINE “go-left” in terms of at least one potential observable or measurable physical phenomenon. Same for “go-right”.

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In the double-slit experiment, if there is no meaning of “the difference between ‘go-left’ and ‘go-right’“, then there is no meaning of “go-left”. (Same for “go-right”.)

In that case, we have only the meaning of “go-through-the-slits (without distinguishing ‘go-left’ and ‘go-right’)“.

We still have that meaning because we can still define

“the photon has gone through the board (that consists of those 2 slits)“

as

“there is a dot appearing on the final screen almost immediately after a photon is emitted from the source“.

— Me@2021-02-03 07:48:01 AM

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quantum information = mathematical information

classical information = physical information

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quantum entanglement

~ all measurement results will be consistent

~ all measurement results follow the three basic logic laws (i.e. identity, non-contradiction, excluded middle)

— Me@2021-01-30 09:46:13 AM

— Me@2021-02-03 12:27:07 AM

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Quantum theory is:

The minimal mathematical formalism that correctly describes all physical interaction as classical information exchange and all classical information exchange as physical interaction.

Entanglement is:

The condition of interacting with the world through an imaginary interface on which classical information appears.

— What Is Entanglement Anyway?

— Chris Fields

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Quantum mechanics is a theory of classical information.

Quantum mechanics explains why all the measurement results are always consistent in spite of the quantum effects, the effects due to the indistinguishabilities of some classical cases.

Quantum mechanics explains why all the measurement results are always consistent in spite of the indistinguishabilities of some classical cases.

— Me@2021-01-28 09:55:56 PM

— Me@2021-02-03 07:48:01 AM

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2021.02.03 Wednesday (c) All rights reserved by ACHK

Cosmic computer

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Consistent histories, 9

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There is a cosmic computer there

which is responsible to make sure that

quantum mechanics (laws) will always give consistent measurement results,

such as the ones of the EPR entangled pairs.

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NO. That is wrong.

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Instead, quantum mechanics itself is THAT cosmic computer that renders all the measurement results consistent.

— Me@2021-01-27 3:54 PM

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2021.01.29 Friday (c) All rights reserved by ACHK

Superposition always exists, 2.2.1

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Decoherence and the Collapse, 2.1 | Quantum decoherence 7.2.1

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But wait! Doesn’t this mean that the “consciousness causes collapse” theory is wrong? The spin bit was apparently able to cause collapse all by itself, so assuming that it isn’t a conscious system, it looks like consciousness isn’t necessary for collapse! Theory disproved!

No. As you might be expecting, things are not this simple. For one thing, notice that this ALSO would prove as false any other theory of wave function collapse that doesn’t allow single bits to cause collapse (including anything about complex systems or macroscopic systems or complex information processing). We should be suspicious of any simple argument that claims to conclusively prove a significant proportion of experts wrong.

To see what’s going on here, let’s look at what happens if we don’t assume that the spin bit causes the wave function to collapse. Instead, we’ll just model it as becoming fully entangled with the path of the particle, so that the state evolution over time looks like the following:

\displaystyle{|O, \uparrow \rangle \to \frac{1}{\sqrt{2}} |A, \downarrow \rangle + \frac{1}{\sqrt{2}} |B, \uparrow \rangle \to \frac{1}{\sqrt{2}}\sum_i \left( \alpha_i | i, \downarrow \rangle + \beta_i |i, \uparrow \rangle \right) = | \Psi \rangle}

…

The interference has vanished, even though we never assumed that the wave function collapsed!

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And all that’s necessary for that is environmental decoherence, which is exactly what we had with the single spin bit!

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A particle can be in a superposition of multiple states but still act as if it has collapsed!

…

You might be tempted to say at this point: “Well, then all the different theories of wave function collapse are empirically equivalent! At least, the set of theories that say ‘wave function collapse = total decoherence + other necessary conditions possibly’. Since total decoherence removes all interference effects, the results of all experiments will be indistinguishable from the results predicted by saying that the wave function collapsed at some point!”

But hold on! This is forgetting a crucial fact: decoherence is reversible, while wave function collapse is not!!!

…

Now the two branches of the wave function have “recohered,” meaning that what we’ll observe is back to the interference pattern!

— Decoherence is not wave function collapse

— MARCH 17, 2019

— SQUARISHBRACKET

— Rising Entropy

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This is the original link:

Decoherence is not wave function collapse

In case the original link does not work, use the Internet Archive version:

https://web.archive.org/web/20210124095054/https://risingentropy.com/decoherence-is-not-wave-function-collapse/

— Me@2021-01-24 07:14:50 PM

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A particle can be in a superposition of …

Note that it is not that the particle is in a superposition. Instead, it is that the system is in a superposition.

— Me@2021-01-24 07:16:49 PM

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2021.01.25 Monday ACHK

Superposition always exists, 2.2.2

Posted on by

Decoherence and the Collapse, 2.2 | Quantum decoherence 7.2.2

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superposition ~ indistinguishability

superposition state ~ logically indistinguishable states (forming one SINGLE quantum state)

logically indistinguishable ~ indistinguishable by definition ~ indistinguishable due to “the experiment setup is without detector” part of the definition

By the Leibniz’s Law (Identity of indiscernibles), logically indistinguishable cases are actually the same one SINGLE case, represented by one SINGLE quantum state.

Classically, there are no such logically indistinguishable cases because classically, all particles are distinguishable. So the probability distribution in the newly invented non-classical state should be completely different from any probability distributions provided by classical physics. Such cases of a new kind are called quantum states.

A quantum state’s probability distribution can be calculated from its wave function.

“Why that single quantum state is represented by a superposition of eigenstates and why its wave function is governed by the Schrödinger equation” is ANOTHER set of questions, whose correct answers may or may not be found in the Wikipedia article Theoretical and experimental justification for the Schrödinger equation.

Superpositions always exist. Logically indistinguishable cases are always there. You just trade some logically indistinguishable cases with some other logically indistinguishable cases.

The “superpositions” are superpositions in definition, in language, in logic, in calculation, and in mathematics, but not in physical reality, not in physical spacetime.

— Me@2021-01-24 09:29:13 PM

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2021.01.24 Sunday (c) All rights reserved by ACHK

… is in a superposition

Posted on by

Quantum decoherence 5.3.2 | Wheeler’s delayed choice experiment 1.2

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For example, in the double-slit experiment, if no detector is installed, the system is in a quantum superposition state.

It is not that each individual photon is in a superposition. Instead, it is that the system of the whole experimental setup is in a superposition.

— Me@2021-01-23 12:57 AM

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[guess]

However, “what ‘the whole experimental setup‘ is” is not 100% objective. In other words, it is a little bit subjective.

“The whole experimental setup”, although largely objective, is partially defined with respect to an observer.

— Me@2021-01-23 12:58 AM

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So quantum probability/indistinguishability effect is partly observer-dependent, although the subjectivity is just tiny compared with that of the classical probability in a mixed state.

— Me@2021-01-23 12:59 AM

[guess]

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2021.01.24 Sunday (c) All rights reserved by ACHK