date:20220427

Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Bruce Kellett

On Thu, Apr 28, 2022 at 3:24 PM Brent Meeker  wrote:

> On 4/26/2022 5:32 PM, smitra wrote:
>
> On 27-04-2022 01:37, Bruce Kellett wrote:
>
> Changing the weights of the components in the superposition does not
> change the conclusion of most observers that the actual probabilities
> are 0.5 for each result. This is simple mathematics, and I am amazed
> that even after all these years, and all the times I have spelled this
> out, you still seek to deny the obvious result. Your logical and
> mathematical skill are on a par with those of John Clark.
>
>
> It's indeed simple mathematics. You apply that to branch counting to
> arrive at the result of equal probabilities.
>
>
I have not used branch counting. Please stop accusing me of that.

> So, the conclusion has to be that one should not do branch counting. The
> question is then if this disproves the MWI. If by MWI we mean QM minus
> collapse then clearly not. Because in that case we use the Born rule to
> compute the probability of outcomes and assume that after a measurement we
> have different sectors for observers who have observed the different
> outcomes with the probabilities as given by the Born rule.
>
>
In which case the Born rule is just an additional arbitrary assumption: it
is not part of the Schrodinger equation. Your theory of QM minus collapse
is not well-defined. You simply take whatever you want from text-book
quantum mechanics, with no regard to the consistency of your model.

> You then want to argue against that by claiming that your argument applies
> generally and would not allow one to give different sectors unequal
> probabilities. But that's nonsense, because you make the hidden assumption
> of equal probabilities right from the start.
>
>
I simply assume the Schrodinger equation. Then, following Everett, we take
it to be deterministic, so that all branches occur on every trial. Since it
is deterministic, there is no concept of probability inherent in the
Schrodinger equation, and I do not assume any definition of probability. So
the branches occur as they occur, there is no assumption of equal
probability. It is just that the construction means that  all 2^N branches
occur on the same basis and necessarily count equally in the overall
branching picture.

There is nothing in QM that says that branches must count equally, and the
> lottery example I gave makes it clear that you can have branching with
> unequal probabilities in classical physics.
>
>
As I have said, there is no classical analogue of an interaction in which
all outcomes necessarily occur. So your lottery example is useless. There
is no concept of probability involved in any of this.

Bruce

>
> Yes, there's nothing in QM that says the branches must count equally.  But
> there's also nothing in the evolution of Schroedingers equation that they
> must count as *a^2* and *b^2*.  Of course IF they are probabilities then
> it follows from Gleason's theorem that they follow the Born rule.  But in
> that case you have reintroduced almost all the philosophical problems of
> the Copenhagen interpretation.  When exactly does this splitting occur?
> Can the split be into irrational numbers of branches?  A splitting is in
> some particular basis and not in other bases.  What determines the pointer
> basis?
>
> Brent
>

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Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Brent Meeker




On 4/26/2022 5:32 PM, smitra wrote:

On 27-04-2022 01:37, Bruce Kellett wrote:

On Tue, Apr 26, 2022 at 10:03 AM smitra  wrote:


On 24-04-2022 03:16, Bruce Kellett wrote:


A moment's thought should make it clear to you that this is not
possible. If both possibilities are realized, it cannot be the

case

that one has twice the probability of the other. In the long run,

if

both are realized they have equal probabilities of 1/2.


The probabilities do not have to be 1/2.  Suppose one million people

participate in a lottery such that there will be exactly one winner.
The
probability that one given person will win, is then one in a
million.
Suppose now that we create one million people using a machine and
then
organize such a lottery. The probability that one given newly
created
person will win is then also one in a million. The machine can be
adjusted to create any set of persons we like, it can create one
million
identical persons, or almost identical persons, or totally different

persons. If we then create one million almost identical persons, the

probability is still one one in a million. This means that the limit
of
identical persons, the probability will be one in a million.

Why would the probability suddenly become 1/2 if the machine is set
to
create exactly identical persons while the probability would be one
in a
million if we create persons that are almost, but not quite
identical?


Your lottery example is completely beside the point.


It provides for an example of a case where your logic does not apply.


I think you
should pay more attention to the mathematics of the binomial
distribution. Let me explain it once more: If every outcome is
realized on every trial of a binary process, then after the first
trial, we have a branch with result 0 and a branch with result 1.
After two trials we have four branches, with results 00, 01, 10,and
11; after 3 trials, we have branches registering 000, 001, 011, 010,
100, 101, 110, and 111. Notice that these branches represent all
possible binary strings of length 3.

After N trials, there are 2^N distinct branches, representing all
possible binary sequences of length N. (This is just like Pascal's
triangle) As N becomes very large, we can approximate the binomial
distribution with the normal distribution, with mean 0.5 and standard
deviation that decreases as 1/sqrt(N). In other words, the majority of
trials will have equal, or approximately equal, numbers of 0s and 1s.
Observers in these branches will naturally take the probability to be
approximated by the relative frequencies of 0s and 1s. In other words,
they will take the probability of each outcome to be 0.5.



The problem with this is that you just assume that all branches are 
equally probable. You don't make that explicit, it's implicitly 
assumed, but it's just an assumption. You are simply doing branch 
counting.


But it shows why you can't use branch counting.  There's no physical 
mechanism for translating the /a/ and /b/ of /|psi> = a|0> + b|1>/ into 
numbers of branches.  To implement that you have put it in "by hand" 
that the branches have weights or numerousity of /a /and /b/.  This is 
possible, but it gives the lie to the MWI mantra of "It's just the 
Schroedinger equation."


Brent





The important point to notice is that this result of all possible
binary sequences for N trials is independent of the coefficients in
the binary expansion of the state:

 .

Changing the weights of the components in the superposition does not
change the conclusion of most observers that the actual probabilities
are 0.5 for each result. This is simple mathematics, and I am amazed
that even after all these years, and all the times I have spelled this
out, you still seek to deny the obvious result. Your logical and
mathematical skill are on a par with those of John Clark.



It's indeed simple mathematics. You apply that to branch counting to 
arrive at the result of equal probabilities. So, the conclusion has to 
be that one should not do branch counting. The question is then if 
this disproves the MWI. If by MWI we mean QM minus collapse then 
clearly not. Because in that case we use the Born rule to compute the 
probability of outcomes and assume that after a measurement we have 
different sectors for observers who have observed the different 
outcomes with the probabilities as given by the Born rule.


You then want to argue against that by claiming that your argument 
applies generally and would not allow one to give different sectors 
unequal probabilities. But that's nonsense, because you make the 
hidden assumption of equal probabilities right from the start. There 
is nothing in QM that says that branches must count equally, and the 
lottery example I gave makes it clear that you can have branching with 
unequal probabilities in classical physics.


Yes, there's nothing in QM that says the branches must count equally.  
But there's also nothing in the evolution of Schroedingers

Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Brent Meeker

On 4/27/2022 10:38 AM, smitra wrote:

On 27-04-2022 04:08, Brent Meeker wrote:

On 4/26/2022 5:32 PM, smitra wrote:

On 27-04-2022 01:37, Bruce Kellett wrote:
On Tue, Apr 26, 2022 at 10:03 AM smitra wrote:

On 24-04-2022 03:16, Bruce Kellett wrote:

A moment's thought should make it clear to you that this is not
possible. If both possibilities are realized, it cannot be the
case
that one has twice the probability of the other. In the long run,
if
both are realized they have equal probabilities of 1/2.

The probabilities do not have to be 1/2. Suppose one million people

participate in a lottery such that there will be exactly one winner.

The
probability that one given person will win, is then one in a
million.
Suppose now that we create one million people using a machine and
then
organize such a lottery. The probability that one given newly
created
person will win is then also one in a million. The machine can be
adjusted to create any set of persons we like, it can create one
million
identical persons, or almost identical persons, or totally different

persons. If we then create one million almost identical persons, the

probability is still one one in a million. This means that the limit

of
identical persons, the probability will be one in a million.

Why would the probability suddenly become 1/2 if the machine is set
to
create exactly identical persons while the probability would be one
in a
million if we create persons that are almost, but not quite
identical?

Your lottery example is completely beside the point.

It provides for an example of a case where your logic does not apply.

I think you
should pay more attention to the mathematics of the binomial
distribution. Let me explain it once more: If every outcome is
realized on every trial of a binary process, then after the first
trial, we have a branch with result 0 and a branch with result 1.
After two trials we have four branches, with results 00, 01, 10,and
11; after 3 trials, we have branches registering 000, 001, 011, 010,

100, 101, 110, and 111. Notice that these branches represent all
possible binary strings of length 3.

After N trials, there are 2^N distinct branches, representing all
possible binary sequences of length N. (This is just like Pascal's
triangle) As N becomes very large, we can approximate the binomial
distribution with the normal distribution, with mean 0.5 and
standard
deviation that decreases as 1/sqrt(N). In other words, the majority
of
trials will have equal, or approximately equal, numbers of 0s and
1s.
Observers in these branches will naturally take the probability to
be
approximated by the relative frequencies of 0s and 1s. In other
words,
they will take the probability of each outcome to be 0.5.

The problem with this is that you just assume that all branches are
equally probable. You don't make that explicit, it's implicitly
assumed, but it's just an assumption. You are simply doing branch
counting.

But it shows why you can't use branch counting. There's no physical
mechanism for translating the _a_ and _b_ of _|psi> = a|0> + b|1>_
into numbers of branches. To implement that you have put it in "by
hand" that the branches have weights or numerousity of _a _and _b_.
This is possible, but it gives the lie to the MWI mantra of "It's just
the Schroedinger equation."

The problem is with giving a physical interpretation to the
mathematics here. If we take MWI to be QM without collapse, then we
have not specified anything about branches yet. Different MWI
advocates have published different ideas about this, and they can't
all be right. But at heart MWI is just QM without collapse. To proceed
in a rigorous way, one has to start with what counts as a branch. It
seems to me that this has to involve the definition of an observer,
and that requires a theory about what observation is. I.m.o, this has
to be done by defining an observer as an algorithm, but many people
think that you need to invoke environmental decoherence. People like
e.g. Zurek using the latter definition have attempted to derive the
Born rule based on that idea.

I.m.o., one has to start working out a theory based on rigorous
definitions and then see where that leads to, instead of arguing based
on vague, ill defined notions.

"Observer as an algorithm" seems pretty ill defined to me. Which
algorithm? applied to what input? How does the algorithm, a Platonic
construct, interface with the physical universe? Decoherence seems much
better defined. And so does QBism.

Brent

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Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Brent Meeker

On 4/27/2022 6:09 PM, Bruce Kellett wrote:
On Thu, Apr 28, 2022 at 10:14 AM Brent Meeker
wrote:

On 4/27/2022 2:00 PM, smitra wrote:

If you agree, and are prepared,
with me, to throw out Everett, then we agree, and there is nothing
more to be argued about (at least, until you present some different
complete theory).

I'm open to the idea that QM itself may only be an approximation
to a more fundamental theory. The arguments in favor of no
collapse are strong arguments but you then do get this issue with
probability that you have discussed here. The disagreement with
you about this is that I don't see it as a fatal inconsistency
that would prove the MWI to be wrong. Probabilities for the
different branches do not have to be equal. But that doesn't mean
that this looks to be a rather unnatural feature of the theory.
This suggests that a more fundamental theory exists from which
one could derive quantum mechanics with its formalism involving
amplitudes and the Born rule as an approximation.

If there are probabilities attached to the branches, then
Gleason's theorem shows that the probabilities must satisfy the
Born rule. So I don't seen any inconsistency in simply saying
they are probabilities of measurement results, that's
Copenhagen. But if they are probabilities of results that implies
that some things happen and others don't...other wise what does
"probability" mean and what use is it as an empirical concept?

That is exactly right. If you try to claim that the probability of
'up' is 90% and the probability of 'down' is 10%, but that both
results certainly happen (albeit on different branches), then you are
talking nonsensical gibberish. That is why I say that Everett is
incompatible with the Born rule.

I'm not such a purist as to hold that probability can't apply to many
things; any measure that satisfies Kolomogorov's axioms qualifies as far
as I'm concerned. So maybe there's some such measure in Everett's
theory, but it seems to have the same problems that were discussed in
1930's. When is a measurement? In Everett the answer seems to be
"Never." Or else it's purely subjective event, as in QBism.

Brent

Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Bruce Kellett

On Thu, Apr 28, 2022 at 10:14 AM Brent Meeker  wrote:

> On 4/27/2022 2:00 PM, smitra wrote:
>
> If you agree, and are prepared,
> with me, to throw out Everett, then we agree, and there is nothing
> more to be argued about (at least, until you present some different
> complete theory).
>
> I'm open to the idea that QM itself may only be an approximation to a more
> fundamental theory. The arguments in favor of no collapse are strong
> arguments but you then do get this issue with probability that you have
> discussed here. The disagreement with you about this is that I  don't see
> it as a fatal inconsistency that would prove the MWI to be wrong.
> Probabilities for the different branches do not have to be equal. But that
> doesn't mean that this looks to be a rather unnatural feature of the
> theory. This suggests that a more fundamental theory exists from which one
> could derive quantum mechanics with its formalism involving amplitudes and
> the Born rule as an approximation.
>
>
> If there are probabilities attached to the branches, then Gleason's
> theorem shows that the probabilities must satisfy the Born rule.  So I
> don't seen any inconsistency in simply saying they are probabilities of
> measurement results,  that's Copenhagen.  But if they are probabilities of
> results that implies that some things happen and others don't...other wise
> what does "probability" mean and what use is it as an empirical concept?
>

That is exactly right. If you try to claim that the probability of 'up' is
90% and the probability of 'down' is 10%, but that both results certainly
happen (albeit on different branches), then you are talking nonsensical
gibberish. That is why I say that Everett is incompatible with the Born
rule.

Bruce

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Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Brent Meeker

On 4/27/2022 2:00 PM, smitra wrote:

If you agree, and are prepared,
with me, to throw out Everett, then we agree, and there is nothing
more to be argued about (at least, until you present some different
complete theory).

I'm open to the idea that QM itself may only be an approximation to a
more fundamental theory. The arguments in favor of no collapse are
strong arguments but you then do get this issue with probability that
you have discussed here. The disagreement with you about this is that
I don't see it as a fatal inconsistency that would prove the MWI to
be wrong. Probabilities for the different branches do not have to be
equal. But that doesn't mean that this looks to be a rather unnatural
feature of the theory. This suggests that a more fundamental theory
exists from which one could derive quantum mechanics with its
formalism involving amplitudes and the Born rule as an approximation.

If there are probabilities attached to the branches, then Gleason's
theorem shows that the probabilities must satisfy the Born rule. So I
don't seen any inconsistency in simply saying they are probabilities of
measurement results, that's Copenhagen. But if they are probabilities
of results that implies that some things happen and others don't...other
wise what does "probability" mean and what use is it as an empirical
concept? That brings back the original problem of CI, where and how is
this happening defined?

Brent

Re: A Superconducting Diode

2022-04-27 Thread Brent Meeker

Terahertz implies wavelengths less than a millimeter.  Computers will 
have to adopt some kind of asynchronous architecture to take advantage 
of that.  I wonder if there are any proposed designs for such computers?


Brent

On 4/27/2022 12:26 PM, John Clark wrote:
In today's issue of the journal Nature researchers report they have 
developed a material that is superconducting in one direction but is a 
normal conductor in the other direction, a superconducting diode, 
something that had previously been thought to be impossible. They used 
a 2D layer of a compound made of bromine and niobium (Nb3Br8) that is 
only a few atoms thick. It only works at liquid helium temperatures, 
3.86K or below, but they're currently working on something that works 
at liquid nitrogen temperatures ,77K, because liquid helium is about 
as expensive as champagne but liquid nitrogen is about as expensive as 
milk. But even at the lower temperature this is a big deal.  Mazhar 
Ali, the chief researcher, is quoted as saying  "/Technology that was 
previously only possible using semiconductors can now potentially be 
made with superconductors using this building block. This includes 
faster computers, as in computers with up to terahertz speed, which is 
300 to 400 times faster than the computers we are now using/."  I'm 
sure this will also be of enormous interest to those wishing to make a 
quantum computer.


The field-free Josephson diode in a van der Waals heterostructure 



John K Clark    See what's on my new list at Extropolis 


asd
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Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Bruce Kellett

On Thu, Apr 28, 2022 at 5:17 AM George Kahrimanis 
wrote:

> On Wednesday, April 27, 2022 at 4:12:12 AM UTC+3 Bruce wrote:
>
> [...]  I spelled out the sequences that Everett implies in my earlier
>> response. These clearly must have equal probability -- that is what the
>> theory requires. It is not an assumption on my part -- it is a
>> consequence of Everett's basic idea.
>
>
> I have already expressed disagreement, as a technical matter. I am not
> certain where the misunderstanding lies, but I suspect it is in presuming
> equal probabilities derived from sheer ignorance, as at least one other
> contributor claims. If you really insist on this opinion, it should be
> discussed in a separate conversation -- appealing to your "logical and
> mathematical skills", as you say.
>

You are right. I should not have used the phrase "equal probability".
Everettian QM does not have a concept of probability, so it is incorrect to
use this term in connection with Everettian branching. It would be more
correct to say that all branches are created on the same basis, or 'all
branches are created equal'. Just as it would be meaningless to claim that
one branch is more probable than some other branch, it is incorrect to say
that any one of the 2^N  branches after N Bernoulli trials is any more
likely than any other branch. All branches are created equal by the method
of construction of the branches as given by Everett.

Bruce

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Re: John K. Clark

2022-04-27 Thread Alan Grayson

I found some stuff about you. Not very interesting, but somewhat 
explanatory. I gather you're subliminally jealous of my relationship with 
Carl Sagan, but for me it's not a big deal. I have a major regret that he 
didn't go through and publish what would have been my third citation during 
that period. I met him (and Pollack) again during Voyager 2's Neptune 
encounter at JPL. That was in 1989. Little did I suspect that five short 
years later Pollack would pass away, and two years later Sagan. AG

On Tuesday, April 26, 2022 at 4:46:24 PM UTC-6 Alan Grayson wrote:

> Do you have an advanced degree in EE? If so, from what University? Are you 
> now retired? Just curious. AG

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Re: Everett and probability

2022-04-27 Thread George Kahrimanis

On Wednesday, April 27, 2022 at 2:55:37 PM UTC+3 johnk...@gmail.com wrote:

> It's not perfect, no analogy is, but classical thermodynamics can provide 
> a pretty good analogy.[...] but that world is *VASTLY* outnumbered by 
> worlds in which other things happen.
>

You mean, statistical mechanics.

Counting worlds, then? I remember as a young student, the "equal 
probabilities" argument based on sheer ignorance of the microstate made me 
depressed. A much better explanation is based on the sort of agument known 
by the name "arbitrary functions", started by Jules Henri Poincaré. Here is 
an example of mine.

Whatever the microstate is (among those compatible with what we know), let 
us focus on the box in which the gas is contained. It has been constructed 
with some procedure, of which we can obtain (with good approximation) 
probability density functions of errors. For example, if we aim to make the 
height to be 4 meters exactly, then we know that the method of construction 
will give us 4 meters plus some error of known distribution. Therefore the 
dimensions of the box are random variables -- even if we assume for the 
time that the surfaces are perfectly flat and it is perfectly orthogonal. 
Every time a gas molecule hits a wall, its future trajectory becomes 
randomised, as well as that of every other molecule it bounces with. Soon a 
probabilistic description of the gas-in-the-box is all we can do, but these 
probabilities are well grounded on the errors in the construction of the 
box.

(If, instead of errors of construction, you prefer to deal with errors of 
measurement, we shall be mired by the controversy in the foundation of 
statistics. Therefore I suggest that we just consider construction.)

George K.

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Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread smitra


On 27-04-2022 04:01, Bruce Kellett wrote:

On Wed, Apr 27, 2022 at 11:35 AM smitra  wrote:


On 27-04-2022 03:11, Bruce Kellett wrote:

On Wed, Apr 27, 2022 at 10:32 AM smitra  wrote:


On 27-04-2022 01:37, Bruce Kellett wrote:


I think you
should pay more attention to the mathematics of the binomial
distribution. Let me explain it once more: If every outcome is
realized on every trial of a binary process, then after the

first

trial, we have a branch with result 0 and a branch with result

1.

After two trials we have four branches, with results 00,

01,10,and

11; after 3 trials, we have branches registering 000, 001, 011,

010,

100, 101, 110, and 111. Notice that these branches represent all
possible binary strings of length 3.

After N trials, there are 2^N distinct branches, representing

all

possible binary sequences of length N. (This is just like

Pascal's

triangle) As N becomes very large, we can approximate the

binomial

distribution with the normal distribution, with mean 0.5 and

standard

deviation that decreases as 1/sqrt(N). In other words, the

majority of

trials will have equal, or approximately equal, numbers of 0s

and 1s.

Observers in these branches will naturally take the probability

to be

approximated by the relative frequencies of 0s and 1s. In other

words,

they will take the probability of each outcome to be 0.5.



The problem with this is that you just assume that all branches

are

equally probable. You don't make that explicit, it's implicitly

assumed,

but it's just an assumption. You are simply doing branch

counting.


The distinctive feature of Everettian Many worlds theory is that

every

possible outcome is realized on every trial. I don't think that

you

have absorbed the full significance of this revolutionary idea.

There

is no classical analogue of this behaviour, which is why your

lottery

example is irrelevant.  I spelled out the sequences that Everett
implies in my earlier response. These clearly must have equal
probability -- that is what the theory requires.


QM without collapse does not require equal probabilities. Branches
are
not a fundamental concept of the theory. You just put this in by
hand.


It is not an assumption on my part -- it is a consequence of

Everett's basic idea.

Everett's (or for that matter any other person's) ideas cannot be
the
basis for doing physics in a rigorous way. Your argument is not
based on
QM without collapse, you are making ad hoc assumptions about
branching
when branching isn't a fundamental process in QM.


So there is no branch counting involved. That is just another red
herring that you have thrown up to distract yourself from the cold
hard logic of the situation.



You just presented an elaborate presentation involving N branching
steps
and counted all 2^N branches as equal. That's branch counting and
it's
known to not be compatible with QM. The MWI can be taken to be QM
without collapse and this is known to be a consistent theory


It would seem that you are claiming that QM without collapse is not
based on Everett's ideas. If you claim that such a theory exists and
is consistent, then you really should present that theory, and point
out that it has nothing to do with Everett, or with obtaining every
outcome of a trial on different branches.

QM without collapse is just that: QM without collapse, nothing more, 
nothing less. Everett worked out this idea added the concept of branches 
and developed an effective theory and also attempted to derive the Born 
rule. But that latter attempt is now recognized to not work and other 
physicists have later used similar and also other approaches to get to a 
derivation of the Born rule. But so far no one has succeeded.



My impression is that you do not have any worked-out theory -- you
just throw arbitrary objections to my working through the consequences
of Everett's approach to quantum mechanics. I have shown that many
problems exist with Everettian QM.


There only exists a problem with getting to the Born rule, not with QM 
without collapse.



If you agree, and are prepared,
with me, to throw out Everett, then we agree, and there is nothing
more to be argued about (at least, until you present some different
complete theory).

I'm open to the idea that QM itself may only be an approximation to a 
more fundamental theory. The arguments in favor of no collapse are 
strong arguments but you then do get this issue with probability that 
you have discussed here. The disagreement with you about this is that I  
don't see it as a fatal inconsistency that would prove the MWI to be 
wrong. Probabilities for the different branches do not have to be equal. 
But that doesn't mean that this looks to be a rather unnatural feature 
of the theory. This suggests that a more fundamental theory exists from 
which one could derive quantum mechanics with its formalism involving 
amplitudes and the Born rule as an approximation.


Saibal



Bruce

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A Superconducting Diode

2022-04-27 Thread John Clark

In today's issue of the journal Nature researchers report they have
developed a material that is superconducting in one direction but is a
normal conductor in the other direction, a superconducting diode, something
that had previously been thought to be impossible. They used a 2D layer of
a compound made of bromine and niobium (Nb3Br8) that is only a few atoms
thick. It only works at liquid helium temperatures, 3.86K or below, but
they're currently working on something that works at liquid nitrogen
temperatures ,77K, because liquid helium is about as expensive as champagne
but liquid nitrogen is about as expensive as milk. But even at the lower
temperature this is a big deal. Mazhar Ali, the chief researcher, is
quoted as saying "*Technology that was previously only possible using
semiconductors can now potentially be made with superconductors using this
building block. This includes faster computers, as in computers with up to
terahertz speed, which is 300 to 400 times faster than the computers we are
now using*." I'm sure this will also be of enormous interest to those
wishing to make a quantum computer.

The field-free Josephson diode in a van der Waals heterostructure

John K ClarkSee what's on my new list at Extropolis

asd

Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread George Kahrimanis

On Wednesday, April 27, 2022 at 4:12:12 AM UTC+3 Bruce wrote:

> The distinctive feature of Everettian Many worlds theory is that every 
> possible outcome is realized on every trial. I don't think that you have 
> absorbed the full significance of this revolutionary idea. There is no 
> classical analogue of this behaviour, which is why your lottery example is 
> irrelevant.

I make no comments on the lottery example, because I would need to 
understand it better, and I have too little time now. But I may suprprise 
you with a parallel from pre-QM philosophical work on the interpretation of 
probability. Cournot's Principle claims that probabilities have no 
interpretation, no relevance to our lives, unless they are close enough to 
0 or 1, "enough" depending on the practical purpose. Before one screams 
"this is crazy", he had better look at the appeal of this idea among the 
most prominent students of these matters in the 20th century. However, what 
little work has been done on a decision theory conforming to this principle 
is patently inadequate, IMO, and this, I think, is the reason for its 
current obscurity. The decision theory I have started for MWI will work for 
Cournot's Principle, too.

If one cares for references, search for "Glenn Shafer" and "Cournot's 
Principle", especially the papers titled
- Why did Cournot’s principle disappear?
- That's what all the old guys said
- A Betting Interpretation for Probabilities and Dempster-Shafer Degrees of 
Belief

[...]  I spelled out the sequences that Everett implies in my earlier 
> response. These clearly must have equal probability -- that is what the 
> theory requires. It is not an assumption on my part -- it is a 
> consequence of Everett's basic idea.

I have already expressed disagreement, as a technical matter. I am not 
certain where the misunderstanding lies, but I suspect it is in presuming 
equal probabilities derived from sheer ignorance, as at least one other 
contributor claims. If you really insist on this opinion, it should be 
discussed in a separate conversation -- appealing to your "logical and 
mathematical skills", as you say.

George K.

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Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread George Kahrimanis

On Wednesday, April 27, 2022 at 5:57:03 AM UTC+3 Bruce wrote:
> If one wants to persist with unitary evolution, one cannot avoid the
Schrodinger equation. This has a number of consequences for the theory. One
is that the theory is deterministic -- there are no probabilities, and all
outcomes of an experiment are, in some real sense, equivalent. [...]

Equivalent in terms of possibility, not equally probable. YOU say "there
are no probabilities".

On Wed, Apr 27, 2022 at 11:35 AM smitra https://groups.google.com/>> (Saibal) wrote:
> You just presented an elaborate presentation involving N branching steps
and counted all 2^N branches as equal. That's branch counting and it's
known to not be compatible with QM.

I agree; it is a technical matter. There are two assumptions in deriving
probability 1/2^N in the binomial construction, if the argument is not
branch-counting:
-1- that probability-in-some-sense is derived by the theory and it depends
on the measure only;
and
-2- that the coefficients a and b are of equal measure.
But with these assumptions we can derive probability-in-some-sense with
just one experiment (N=1).

In previous messages, I have expressed objection to the first assumption,
but this is only because some work is needed in order to combine "there are
no probabilities" with "there are probabilities in some sense", else one is
vague to the point of being ridiculous. One needs to specify "in what
sense?" and "why?".

George K.

Everett and probability

2022-04-27 Thread John Clark

On Tue, Apr 26, 2022 at 9:12 PM Bruce Kellett wrote:

*> The distinctive feature of Everettian Many worlds theory is that every
> possible outcome is realized on every trial. I don't think that you have
> absorbed the full significance of this revolutionary idea. There is no
> classical analogue of this behaviour*

It's not perfect, no analogy is, but classical thermodynamics can provide a
pretty good analogy. There is an initial condition microstate for the room
that I'm in right now that, at the macrostate level, looks pretty much like
any other macrostate; however, just due to the laws of classical physics
that particular microstate is such that in 30 seconds all the air in the
room will gather in a one square foot volume in the lower left corner of
the room, and as a result I suffocate to death.

The particular microstate that would cause that to happen is no more
unlikely to occur than any other microstate, but it is *VASTLY* outnumbered
by microstates in which it doesn't happen. So the odds that the room that
I'm in right now just happens to be in that one particular microstate are
ridiculously low, but they are not zero. So if you were a bookie you could
probably make quite a lot of money by betting that John Clark will not
suffocate in the next 30 seconds, but there is a very small chance you will
not. The difference with the classical is that in the Everettian view every
possible outcome is realized, so there is a world it which Bruce Kellett
makes different life choices in his youth and decides to become a bookie
and John Clark suffocates to death and bookie Bruce Kellett loses money,
but that world is *VASTLY* outnumbered by worlds in which other things
happen.

John K ClarkSee what's on my new list at Extropolis

Re: The Nature of Contingency: Quantum Physics as Modal Realism

2022-04-27 Thread Bruce Kellett

On Wed, Apr 27, 2022 at 3:43 PM Brent Meeker  wrote:

> On 4/26/2022 7:56 PM, Bruce Kellett wrote:
>
> On Wed, Apr 27, 2022 at 12:32 PM Brent Meeker 
> wrote:
>
>> On 4/26/2022 7:01 PM, Bruce Kellett wrote:
>>
>> On Wed, Apr 27, 2022 at 11:35 AM smitra  wrote:
>>
>>>
>>> You just presented an elaborate presentation involving N branching steps
>>> and counted all 2^N branches as equal. That's branch counting and it's
>>> known to not be compatible with QM. The MWI can be taken to be QM
>>> without collapse and this is known to be a consistent theory
>>
>>
>> It would seem that you are claiming that QM without collapse is not based
>> on Everett's ideas. If you claim that such a theory exists and is
>> consistent, then you really should present that theory, and point out that
>> it has nothing to do with Everett, or with obtaining every outcome of a
>> trial on different branches.
>>
>> My impression is that you do not have any worked-out theory -- you just
>> throw arbitrary objections to my working through the consequences of
>> Everett's approach to quantum mechanics. I have shown that many problems
>> exist with Everettian QM. If you agree, and are prepared, with me, to throw
>> out Everett, then we agree, and there is nothing more to be argued about
>> (at least, until you present some different complete theory).
>>
>>
>> I think Everett's idea was just to get rid of wave-function collapse and
>> instead assert that the apparently incompatible results of an experiment
>> were just different entanglements of one's brain/instrument with different
>> superposed components of the state of the system measured.  This is all
>> consistent with the Copenhagen interpretation, except in CI all but one of
>> the orthogonal components is discarded.  Decoherence has cast some light on
>> why the components quickly become orthogonal and why they become orthogonal
>> only in certain bases.
>>
>
> An important component of Everett's idea was that quantum evolution was
> unitary. That gave centrality to the Schrodinger equation. If one wants to
> persist with unitary evolution, one cannot avoid the Schrodinger equation.
> This has a number of consequences for the theory. One is that the theory is
> deterministic -- there are no probabilities, and all outcomes of an
> experiment are, in some real sense, equivalent. That leads to the
> consequences that I have pointed out. If Saibal wants to avoid those
> consequences, then he has to abandon the idea of unitary evolution and the
> Schrodinger equation. I think Saibal would be reluctant to go down that
> path, so he is left with an inconsistent mess.
>
>
> I don't see that it's inconsistent.  It's just like QBism.  You get a
> result and you renormalize the wf.  Whether the other outcomes occur in
> some platonic world, is irrelevant.
>

OK. SO it is much more like a subjective interpretation such as QBism than
it is based on Everett. Since you do not have a single consistent wave
function in QBism, it is Okay in that theory to simply ignore
inconsistencies. as Saibal does.

Bruce

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Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: A Superconducting Diode

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: John K. Clark

Re: Everett and probability

Re: The Nature of Contingency: Quantum Physics as Modal Realism

A Superconducting Diode

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Re: The Nature of Contingency: Quantum Physics as Modal Realism

Everett and probability

Re: The Nature of Contingency: Quantum Physics as Modal Realism

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