Bell Nonlocality Is Not Sufficient for the Security of Standard Device-Independent Quantum Key Distribution Protocols

[Richard Gill]

Dear all

Preparing for a conference talk in London next week, I've started learning about Device Independent Quantum Key Distribution. I wonder if any of the group is interested in learning more about this topic with me?

I came across a fascinating paper with a negative result:

Bell Nonlocality Is Not Sufficient for the Security of Standard Device-Independent Quantum Key Distribution Protocols
Máté Farkas, Maria Balanzó-Juandó, Karol Łukanowski, Jan Kołodyński, and Antonio Acín
Phys. Rev. Lett. 127, 050503 – Published 29 July 2021

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.050503

See synopsis: Testing the Security of Quantum Key Distribution https://physics.aps.org/articles/v14/s94

 
ABSTRACT

Device-independent quantum key distribution is a secure quantum cryptographic paradigm that allows two honest users to establish a secret key, while putting minimal trust in their devices. Most of the existing protocols have the following structure: first, a bipartite nonlocal quantum state is distributed between the honest users, who perform local projective measurements to establish nonlocal correlations. Then, they announce the implemented measurements and extract a secure key by postprocessing their measurement outcomes. We show that no protocol of this form allows for establishing a secret key when implemented on any correlation obtained by measuring local projective measurements on certain entangled nonlocal states, namely, on a range of entangled two-qubit Werner states. To prove this result, we introduce a technique for upper bounding the asymptotic key rate of device-independent quantum key distribution protocols, based on a simple eavesdropping attack. Our results imply that either different reconciliation techniques are needed for device-independent quantum key distribution in the large-noise regime, or Bell nonlocality is not sufficient for this task.

The other recent papers on this topic are fascinating too. There is a lot of hype but also sobering results. One of them includes these statements:

Using a hybrid system where heralded entanglement between stationary trapped ion qubits is established via flying photonic qubits (see Fig. 1), we are able to generate high-quality entangled states between two ions separated by about 2 m, resulting in a record-high detection-loophole-free Bell inequality violation with isolated systems.

but also:

Table I: Secret key balance sheet. The experiment requires an initial 1 203 422-bits long key K0 shared between Alice and Bob. 256 of these bits are consumed by the protocol while generating 95 884 new secret shared bits. This results in the creation of a longer 1 299 050-bits long shared secret key K1 = K′A between Alice and Bob, effectively extending the initial key by 95 628 bits.

Device-Independent Quantum Key Distribution
D. P. Nadlinger et al.

https://arxiv.org/abs/2109.14600

[Jan-Åke Larsson]

Hi,

The DIQKD thing is a mess, I wouldn't trust systems based on this more than standard BB84 where you need to put full trust in both source and detector. The problem is that you may have full trust in one part of a system, but that the properties of the rest of the system makes that irrelevant.

Best
Jan-Åke

[Austin Fearnley]

Dear Richard

About the DIQKD statement you found:

"Using a hybrid system where heralded entanglement between stationary trapped ion qubits is established via flying photonic qubits (see Fig. 1), we are able to generate high-quality entangled states between two ions separated by about 2 m, resulting in a record-high detection-loophole-free Bell inequality violation with isolated systems."

Is this serious?  Or does  "flying photonic cubits" ==>  pink elephants?

And
"... resulting in a record-high detection-loophole-free Bell inequality violation with isolated systems."

Is this newspeak or has the Bell test method moved on so fast since 2015 that there are new bona fide Bell experiments (like this one?) replicating the 2015 findings?  Or is "record -high" not really very high?  And how does this fit in with Chantal and Pierre's current doubtfulness of the findings of the 2015 experiments in favour of a higher than classical Bell experiment correlation?

I am dubious of the above DIQKD statement because my retrocausal method for Bell shows that there is nothing spooky about entanglement and entanglement is not responsible for the 0.707 correlation.  However, retrocausality could provide 0.707 correlation in a real experiment which could maybe be used somehow in private signalling issues, though I doubt it.  The photons would not need to be entangled but merely either similarly or oppositely polarised.

Austin

[Richard Gill]

Dear Austin, I haven’t studied the paper in detail yet so I don’t know the answers to your questions…

Richard

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[Richard Gill]

Austin: They had S = 2.677 with standard error 0.007 based on 2 million Bell pairs.

The experiment does not *replicate* the 2015 findings since the distance between the two qubits is very small (2 meters). As they say, they have a very good detection-loophole-free result. The locality loophole is not closed.

The result is better in some respects, less good in others.

Notice, it is an experiment like Munich and Delft, so it is actually a three party Bell-type experiment, not a classical two party Bell experiment.

Photons fly (through glass fibre cables) from Alice and Bob’s trapped 88Sr+ atoms to Charlies location where they interfere and altogether, four detectors are placed.

Entanglement swapping.

It’s all very classical by now.

On 17 Jun 2022, at 17:47, Austin Fearnley <ben...@hotmail.com> wrote:

[Richard Gill]

[Austin Fearnley]

Dear Richard

Thank you for finding those experiment results.  S = 2.7 is equivalent to quite close to (absolute) r = 0.7.  So I should take back some of my scepticism about this field.  Thank you also for finding the experimental design image, though I am very out of my depth with details of real experiments.  I try to think about very simple designs with Alice and Bob only, so I usually switch off when Charlie is used. Likewise the use of two settings for each of Alice and Bob is too 'over the top for me' and I usually consider only a=0 deg and b=45 deg rather than random device settings.  And I ended by using 365 systematic particle polarisations rather than use a random number generator a million times.  This is because I am only simulating correlation disattenuation rather than simulating a complicated Bell experiment.  But I do realise that the above complications are necessary in continually improved real Bell experiments, though not in my simple or toy simulations.

IMO one cannot, in a simulation, get a disattenuated 0.707 correlation by rounded 'measurements' of particle polarisations used as local hidden variables through normal physics.  One can get 0.707 by simply rearranging the +1 and -1 readings on the post-experiment results chart but IMO that is throwing out locality, not to mention 'cheating'.

If retrocausality of antiparticles is a correct method then nature is sending messages FTL, and if nature is doing this then man can try to utilise it.  To be  clearer {I do have a draft paper on 'time and retrocausality' but I am not inclined to find the energy to complete it} the effect is layered.  It is FTL in universal or macroscopic time, i.e. the thermodynamic arrow of time, but it is not FTL in particle time or antiparticle reversed time due to local transmission at less than or equal to the speed of light.  

Austin

On Friday, June 17, 2022 at 5:34:12 PM UTC+1 Richard Gill wrote:

[Richard Gill]

Nature is very, very cunning. QM appears to be non-local but the apparent non-locality does not generate action at a distance. There is no conflict with relativity.

And indeed: we can utilise these cunning features.

One can use entanglement to send messages instantaneously over great distances … only the message arrives encoded, and the key to decode it is classical information, which has to be sent by classical slower than light communication. Hence you cannot act on the message even though you got it kind-of before it was sent (depends on choice of inertial frame)

You can use it to create correlated secret randomness, as is done in those experiments. Nadlinger et al. used 1 million secret random bits already shared between Alice and Bob in order to create a further hundred thousand shared between them too, and guaranteed by the laws of nature to be unavailable to anyone else. As long as nobody can find a loophole in their experiment ...

https://arxiv.org/abs/2109.14600

Device-Independent Quantum Key Distribution
D. P. Nadlinger, P. Drmota, B. C. Nichol, G. Araneda, D. Main, R. Srinivas, D. M. Lucas, C. J. Ballance, K. Ivanov, E. Y-Z. Tan, P. Sekatski, R. L. Urbanke, R. Renner, N. Sangouard, J-D. Bancal

The paper has 15 authors. I don’t know most of them, but one of them, Renato Renner (Zürich) is a very, very good theoretician.

The first author David Nadlinger <david.n...@physics.ox.ac.uk> is in Oxford. He seems to be a PhD student. Got his masters from ETH in 2013. Is co-author of more than 10 serious papers so far, but first author of only couple.

https://www.physics.ox.ac.uk/our-people/nadlinger/publications

[Mark Hadley]

I'd like to  highlight a subtlety that may be confusing the debate.

In the absence of a satisfactory agreed explanation of QM we can make a pragmatic statement:

PRAGMATIC

The wavefunction is a type of probability function which allows us to make probabilistic predictions of the outcomes of experiments. 

I'd say that is a FACT 

INSTRUMENTALIST 

Adds that predicting the outcomes of experiments is all that matters. 

That's a philosophical point of view and a convenient one for scientists using QM for other work ( not foundations) 

For my part I recognise the pragmatic statement, but don't subscribe to the instrumentalist view. As I read it, Akexey's referee had the same position. 

Isham's book makes the same distinction. 

Cheers

Mark

[Richard Gill]

Dear Mark, I agree with you, except on terminology. Please define “probability function”. (I’m a mathematician, probabilist, and statistician. I never met the term before. Is it common terminology in physics? Philosophy of science?)

Richard

PS It could be a very useful term but it needs some anchoring in the languages of relevant scientific disciplines).

Sent from my iPhone

On 18 Jun 2022, at 12:29, Mark Hadley <sunshine...@googlemail.com> wrote:



[Mark Hadley]

Good point.

It's a function that can be used to calculate probabilities.

Of course, classically that would be a density function over configuration space. With the probability being the weighted volume integral. 

I personally don't think physicists have the right to change the rule for defining probabilities, any more than deciding 3+5 neq 8 for large distances for example.

My challenge, using time reversal, is to put quantum probability into the classical equations. Probably with a context dependrnt trajectory theory.

Cheers

Mark

[Richard Gill]

OK, so how about:

PRAGMATIC
The wavefunction is a function which allows us to make probabilistic predictions of the outcomes of experiments. 

[One could also introduce the new term “probability amplitude”].

*******************

In present day probability theory, one has probability measures. They are: nonnegative measures on a sigma algebra of subsets of a set Omega, with total mass equal to one. So that definition refers back to measure theory and to set theory.

Sometimes, in physics, Omega might be thought to be “configuration space”. But Kolmogorov didn’t intend probability theory to be limited to physical applications. It also applies to Bayesian probability where the sigma algebra is a set of propositions which is closed under certain abstract operations, and P(A) means “degree of belief in A”. The set Omega is a set of “atomic propositions”. It need not correspond to “configurations” of a physical system. Kolmogorov kept quiet about that possible application of his axioms and the theory built on those axioms.

The word “density function” has a much bigger meaning in measure theory. A “probability density” is nowadays just a Radon-Nikodym derivative. Kolmogorov’s genius was to recognise that the Radon-Nikodym theorem (Nikodym was a Polish mathematician and he established the general result only in 1930) allowed to provide a rigorous and abstract definition of conditional expectation value, and hence also of conditional probability distribution, extending Borel’s earlier attempts to found probability theory in then nascent measure theory, and Radon’s 1913 version of the theorem, only proven for Euclidean spaces. (Radon was an Austrian mathematician).

****************

Kolmogorov had some problems with writing and publishing his 1933 book (published in German, in Germany) on the foundations of probability theory, which ostensibly answered one of Hilbert’s 21 fundamental questions for the 20th century. You could say that von Neumann’s treatise answered the same question! Kolmogorov needed hard currency for the repair of his dacha. The Marxist-Leninists who were running the USSR did not believe in randomness or probability. Marx’s laws were deterministic laws of society. They stopped Soviet scientists from working in many areas of science and academia because of perceived conflicts with Marxist-Leninist thought. Kolmogorov was called up to explain himself to the appropriate minister of science. He explained that the Soviet run state lottery relied on the rules of probability theory which he had exposed and embedded in modern mathematics. So he got off the hook. Otherwise, history might have been very different.

Alexander Shiryayev later became Kolmogorov’s scientific heir, and also heir to his dacha. Shiryayev was one of the main mathematicians building the martingale based theory of stochastic integration and I have had a lot of personal contacts with him. Kolmorogov’s probability theory became the basis of Doob’s work on martingale theory which became the basis of my PhD research on applications to “survival analysis”. 

Later I had a lot of contacts with Slava Belavkin and with Alexander Holevo. Holevo made incredible contributions to quantum information theory, before the term was invented. Belavkin also made important contributions, in particular to quantum stochastic processes, filtering and control. Belavkin and Holevo were students of two different Russian professors who seem to have been personal enemies, or at least, competitors. Holevo was a student of Romanov, Romanov of Kolmogorov. Belavkin was a student of Stratonovich, whose adviser is unknown, and who was formally a physicist. Stratonovich maybe wrote the first works on quantum information, but the topic was suppressed by the authorities, so he restyled his work as being about radio waves.

Belavkin’s mother came from Lviv or Lvov or Lemburg, presently in Ukraine, but who knows where it will be next. She lived all her life in the same place, but in 10 different countries as the years went by.

Maybe Alexey can tell us more about the histories of Holevo and of Belavkin

Richard

[Mark Hadley]

Agreed that's an improvement to my wording. Interesting discourse on probability.

My understanding is that QM probabilities break the Kolmogorov rules, because the proposition lattice is ortho modular and not distributive. Have I got that right? 

Cheers

Mark

[Richard Gill]

You can say that.

There is a formal mathematical sense in which quantum probability is a generalisation of classical probability

I would say that there is a sense in which quantum probability is a specialisation of classical statistics - because statisticians study families of alternative classical probability models for classical data

I have worked on quantum versions of the LeCam theory of comparison of statistical experiments, and convergence of statistical experiments. My PhD students and postdocs and collaborators did fantastic work.

LeCam studied a sequence of statistical models and derived a meaningful way to say that they converge to a limit experiment (often a Gaussian shift experiment).

We studied a sequence of quantum statistical models (family of possible quantum states + all possible measurements gives a family of classical statistical models, with some special structure relating different members of the same family). Proved limit theorems.

See for instance Kahn and Guta https://arxiv.org/abs/0804.3876

Local asymptotic normality for finite dimensional quantum systems

Yamagata, Fujiwara and Gill https://arxiv.org/abs/1210.3749

Quantum local asymptotic normality based on a new quantum likelihood ratio

My favourite own paper with some of this flavour is

Gill and Guta https://arxiv.org/abs/1112.2078

On Asymptotic Quantum Statistical Inference

I think it contains the deepest and hardest mathematical result I ever managed to prove. I missed the deadline for resubmitting a revised version to the premier journal of mathematical statistics because I was too focussed on a suspected killer nurse. This also cost me one of my potentially best PhD students Sonja Cox, working with me on forensic DNA (who I neglected too much). Still, she went on to build an excellent career...

[Richard Gill]

Some other important Russians are Ildar Ibragimov and Rafael(?) Hasjminskii. Formerly based in former Leningrad. A Tatar and a Jew, they did path breaking work in mathematical statistics, but not being ethnic Russians in Moscow, they had a hard time in Soviet Russia. Both emigrated to the West when they had a chance. They had numerous brilliant students, among them my former colleague and collaborator, Boris Levit (born in Moldova). Their work has had enormous influence in mathematical statistics. Russia’s loss was the West’s gain. Levit was a “refusenik”. Being Jewish, he could not get proper employment in Soviet Russia, yet his application to emigrate to Israel was refused. An absolutely brilliant and original mathematician. Now located in Canada, via a couple of years in Netherlands

https://projecteuclid.org/journals/bernoulli/volume-1/issue-1-2/Applications-of-the-van-Trees-inequality--a-Bayesian-Cram%C3%A9r/bj/1186078362.full

I used this work in my own exploration of quantum Cramer-Rao bounds.

Sent from my iPhone

On 18 Jun 2022, at 14:08, Mark Hadley <sunshine...@googlemail.com> wrote:



[Austin Fearnley]

Dear Richard

I have looked at the Nadlinger et al paper you referred to.  I half understood in some places.  Figure 2 of the DIQKD protocol structure was so complex and it reminded me of the complexity of the large prime number keys protocol which I saw for the first time, years ago, in the Scientific American.  I have no idea how the trapped ions generate entangled photons.  The blurb under Figure 1 was helpful.  Also, Figure 3 showed that the S statistic average of 2.67 was maintained, impressively IMO, in a stable sequence of moving averages rather than just being a one-off statistic. If retrocausality is the answer to Bell then each pair of photons must be photon & antiphoton, whereas I have only dealt with electron & positron Bell pairs previously.

There is an issue about retrocausality of photons.  Photons are generally regarded to be their own antiphotons.  It is  much simpler with fermions.  There is a LH and RH electron and a corresponding RH and LH positron, with four different chiral structures.  In my preon model a LH electron is ACBB' whereas the RH positron is A'C'B'B  where the apostrophe indicates an antipreon. So electrons and positrons are easily identifiable as particle and antiparticle in the preon structure.  But in my preon model, photons only have two forms:  B'B'CC and BBC'C' and, although one is indeed the antiparticle of the other, yet it is not straightforward to say which is the particle as they are each a fifty-fifty mix of preons and antipreons.  And, consequently, each photon  is travelling forwards and backwards in time simultaneously.  What is normally said is that a photon does not travel through time in its own frame as it travels completely through space alone.  But in our frame a photon can travel from the sun to the earth in about eight minutes ...  so it is passing through 'our' time.

This mix of forwards and backwards in time can help in a Bell simulation (though I have never even thought of using photons before).  This mix matches the Advanced and Retarded waves idea which Feynman used in his QED PhD thesis.  Instead of picking out the time direction of the whole particle or boson, I can pick out which preons are travelling which way through time.  So, for the LH electron, there are A and C preons travelling forwards in time.  One can ignore the BB' as they are exactly neutral in everything but mass, so the B' effectively cancels out the B.  Preon A carries the -0.5 spin of this LH electron.  Likewise, Preon A' carries the +0.5 spin of the partner RH positron.  Applying this idea to the B'B'CC photon the B'B' preons are travelling backwards in time each with spin 0.5 making a total spin of +1 for this photon.  The other photon has preons BB travelling forwards in time with total spin -1.   Preons C and C' do not have any spin attribute.  This is good news for me as the photon can be used to transmit spin retrocausally in a Bell experiment, despite the photon not experiencing the passage of time in its own frame.

Austin

[Richard Gill]

On 18 Jun 2022, at 23:17, Austin Fearnley <ben...@hotmail.com> wrote:

I have no idea how the trapped ions generate entangled photons.

https://arxiv.org/abs/2109.14600

Device-Independent Quantum Key Distribution
D. P. Nadlinger, P. Drmota, B. C. Nichol, G. Araneda, D. Main, R. Srinivas, D. M. Lucas, C. J. Ballance, K. Ivanov, E. Y-Z. Tan, P. Sekatski, R. L. Urbanke, R. Renner, N. Sangouard, J-D. Bancal

There are two ions, suspended in ion traps, some distance apart, belonging to Alice and Bob

Each is excited by a pulse from a laser, and each emits a photon.

Each emitted photon is entangled with the ion which it left behind. [Each photon and each atom has a binary property modelled with a two dimensional Hilbert space.]

The two photons now meet at a polarising beam splitter, belonging to Carol, where they interfere. 

Carol measures two emerging photons. Basically their states are Alice + Bob, and Alice - Bob

Carol sees two binary outcomes. Given a particular outcome pair (say: +, +) the two ions are now in the Bell state.

So one quarter of the times, Alice and Bob’s two ions are in a particular one of the four maximally entangled Bell states  |+ ->  +/-  |- +>   and   |+ +>  +/-  |- -> . These four are an orthonormal basis of C^2 otimes C^2

Alice and Bob do their measurements on their ions every time, anyway. As I said, one finally collects the data and studies the correlations between Alice’s and Bob’s outcomes x and y given their settings a and b and given Carol’s outcome z, for the chosen value of z.

This is old stuff. On wikipedia you can find a description. I don’t like their terminology and notation, but you should be able to rewrite it in a better way. 

Nadlinger et al omit step 5 is omitted, and step 6 is: Alice and Bob have a Bell pair between qubits A2 and B2 on those occasions that Carol got a particular respecified outcome (one of the four possible).

https://en.wikipedia.org/wiki/Quantum_teleportation#Entanglement_swapping

Algorithm for swapping Bell pairs[edit]

An important application of entanglement swapping is distributing Bell states for use in entanglement distributed quantum networks. A technical description of the entanglement swapping protocol is given here for pure bell states.

1. Alice and Bob locally prepare known Bell pairs resulting in the initial state:
   {\displaystyle |\psi \rangle _{\rm {in}}=|\Phi ^{+}\rangle _{A_{1},A_{2}}|\Phi ^{+}\rangle _{B_{1},B_{2}}}
2. Alice sends qubit {\displaystyle A_{1}} to a third party Carol
3. Bob sends qubit {\displaystyle B_{1}} to Carol
4. Carol performs a Bell projection between {\displaystyle A_{1}} and {\displaystyle B_{1}} that by chance results in the measurement outcome:
   {\displaystyle \langle \Phi ^{+}|_{A_{1},B_{1}}|\psi \rangle _{\rm {in}}=|\Phi ^{+}\rangle _{A_{2},B_{2}}}
5. In the case of the other three Bell projection outcomes, local corrections given by Pauli operators are made by Alice and or Bob after Carol has communicated the results of the measurement.
   {\displaystyle \langle \Phi ^{-}|_{A_{1},B_{1}}|\psi \rangle _{\rm {in}}={\hat {Z}}_{B_{2}}|\Phi ^{+}\rangle _{A_{2},B_{2}}}
   {\displaystyle \langle \Psi ^{+}|_{A_{1},B_{1}}|\psi \rangle _{\rm {in}}={\hat {X}}_{B_{2}}|\Phi ^{+}\rangle _{A_{2},B_{2}}}
   {\displaystyle \langle \Psi ^{-}|_{A_{1},B_{1}}|\psi \rangle _{\rm {in}}={\hat {X}}_{B_{2}}{\hat {Z}}_{B_{2}}|\Phi ^{+}\rangle _{A_{2},B_{2}}}
6. Alice and Bob now have a Bell pair between qubits {\displaystyle A_{2}} and {\displaystyle B_{2}}
   {\displaystyle |\psi \rangle _{\rm {out}}=|\Phi ^{+}\rangle _{A_{2},B_{2}}}

[Richard Gill]

Austin, you can learn about quantum teleportation from my 2001 paper in the Journal of the Korean Statistical Society.

Entanglement swapping is just one simple application of the same trick

https://www.koreascience.or.kr/article/JAKO200111920784848.pub?&lang=en

https://arxiv.org/abs/math/0405572

[Austin Fearnley]

Dear Richard


Thanks for the information.  You are very patient with me on what for you is  'old stuff' though I may not have the stamina to go much further!  I have looked at the wiki page on teleportation of information.

IMO the 'no-communication' limit has to be dropped if retrocausality allows (apparent) FTL communication.  Information is already being communicated between Alice and Bob instantly due to Bells' retro effects at quantum level.  I suspect that people are, or ought to be, already working out how to ditch the classical channel in the protocol.  Perhaps using multi-layers of teleportation protocols to send that classical information by Bell teleportation routes instead.

I need to look up more on beam-splitters.  For my retro method it is important that beam-splitters are producing photons and antiphotons (BBC'C' and B'B'CC respectively in my preon model).  I have managed to model, using preons, all of the many decay modes that I have attempted.  It is misleading IMO to think that an amorphous energy alone can produce new particles.  It requires energy + preons in the vicinity and/or in the vacuum fields, particularly from various generations of higgs fields.  So I need to work out the beam-splitter interaction(s) in terms of preons.

I note that step 5 in the entanglement swapping algorithm contains the words 'local corrections' which seems iffy, but note that this step was dropped by Nadlinger et al.  Bell implies entanglement, but a correlation of 0.707 after "local corrections" would not necessarily mean as much entanglement was present as calculated. I am slightly more wary of Nadlinger's S = 2.67 result after reading all this background, despite their dropping of Step  5.  But I know very little in this area.

I will look at your Korean paper soon, thanks.

Austin

[Mark Hadley]

I have a hidden variable model and want to put a probability structure on it, but I don't know how.

In brief:

particles take a trajectory in space time through the apparatus. There are local equations for the trajectory with the actual path also dependent on some unknown initial conditions like position and velocity. All very simple and classical. But the local equations depend upon the measurement apparatus boundary conditions.

How can I apply a classical sort of probability to the particles?

Cheers

Mark

[Richard Gill]

Do look at the Korean paper.

At step 5 as described on Wikipedia, Alice and Bob possess two qubits jointly in one of each of the four Bell states depending on Carol’s measurement outcome (four possible outcomes).

Nadlinger et al don’t do teleportation: they just use one of the four states. They simply discard a quarter of the trials. They study the correlations between x and y given settings a and b and given Carol’s outcome z, for just one of the four possible values of z.

People who do teleportation have a further classical communication step …


Sent from my iPad

[Richard Gill]

Here is another interesting recent work on using entanglement swapping to generate entanglement over large distances.

https://arxiv.org/abs/2103.11454

Improved analytical bounds on delivery times of long-distance entanglement

Tim Coopmans, Sebastiaan Brand, David Elkouss

The ability to distribute high-quality entanglement between remote parties is a necessary primitive for many quantum communication applications. A large range of schemes for realizing the long-distance delivery of remote entanglement has been proposed, both for bipartite and multipartite entanglement. For assessing the viability of these schemes, knowledge of the time at which entanglement is delivered is crucial. Specifically, if the communication task requires multiple remote-entangled quantum states and these states are generated at different times by the scheme, the earlier states will need to wait and thus their quality will decrease while being stored in an (imperfect) memory. For the remote-entanglement delivery schemes which are closest to experimental reach, this time assessment is challenging, as they consist of nondeterministic components such as probabilistic entanglement swaps. For many such protocols even the average time at which entanglement can be distributed is not known exactly, in particular when they consist of feedback loops and forced restarts. In this work, we provide improved analytical bounds on the average and on the quantiles of the completion time of entanglement distribution protocols in the case that all network components have success probabilities lower bounded by a constant. A canonical example of such a protocol is a nested quantum repeater scheme which consists of heralded entanglement generation and entanglement swaps. For this scheme specifically, our results imply that a common approximation to the mean entanglement distribution time, the 3-over-2 formula, is in essence an upper bound to the real time. Our results rely on a novel connection with reliability theory.

https://journals.aps.org/pra/abstract/10.1103/PhysRevA.105.012608

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[Austin Fearnley]

Dear Richard

Excuse my slow pace.  I have now given your Korean Statistical Society paper/tutorial one (light) reading and it has helped (just a little though) my thinking. (I did not read the arxiv version.)  It is a very clear and readable paper.  Some posts by Alexey are also very enjoyable reading, especially his latest one re Mermin.  I have also read your recent Gull slides, and previously followed your progress on the maths of the Gull method. I will return to read your Korean paper again later.

I have followed excellent, mathematical online courses on QM and entanglement by Susskind, but I prefer to work with my preon model and particles.  I have come over the last decade to be suspicious of QM (maybe QM itself is "lost in maths"?) and entanglement and have ignored any work on 'teleportation'.  So I have a lot to catch up on, if indeed I ever do catch up!  My work in the last two years on retrocausality has however made me realise that quantum teleportation of 'information' may actually be happening in nature in a Bell experiment.  So I have recently changed my view on teleportation.

After reading your Korean paper I think I now understand Step 5 of 'entanglement swapping' better,  but I am at an early stage of thinking and am still very suspicious.  

I also am not convinced by the randomness issue at the end of your 2.1: 'The Qubit'.  I have built preons in my model that do have the chiral state permanently.  Permanently means: between particle interactions.  So I need a left-handed electron and also a right handed electron as different individual chiral structures.  It may be that QM treats the real electron as a mix of the two chiralities, but not in my particle model.  Of course, an observer in a different frame than the electron can see a LH electron and observe it to be RH because of the helicity property which is a combination of observer and chiral electron effects.  But IMO the RH observation is not a change to the particle's real chiral LH structure, which is permanent.  Well actually, the observer sees it a RH and at a measurement it will change afterwards from LH chirality to RH chirality, which a new observer can see as either LH or RH depending on his/her frame.  So the randomness is not a property of the chiral structure of the electron but of the change in helicity depending on the observer's frame or point of view. There is no randomness in the chiral structure only the variability of the helicity.  So this is a problem for 'free will' as outcomes are derived deterministically.  It is easier for photons as the helicity always equals the chirality because of speed c.  (I know Joy disagrees with me on this.  In an S3 model, the issue of chirality is  (maybe parodied?) by observers not knowing in which of the two covers of the universe a particle is actually resident.)

I have another worry about Step 5 which I will think about further.  


Austin

[Austin Fearnley]

Dear Richard

I have found what appears to me a good source of information by Weihs and Zeilinger:
https://copilot.caltech.edu/documents/16791/weihs_zeillinger_photon_statistics_at_beamsplitters_qip.pdf

Quoting from their page xix on entanglement swapping:
"Entanglement used to be considered as a consequence of the fact that the entangled particles interacted in their past or that they came from a common source.  That this is too restricted a view is witnessed by the concept of entanglement swapping ..."

So it is no use my trying to find a common source of pairs in entanglement swapping or in a polarising beam splitter.
Without a common source or interaction in the past there is no way (that I know of yet) for the 'reversed time' spin (of photon B'B'CC)  passing its information to the forwards in time spin photon BBC'C') .. using my preon model.

Photons produced by parametric down conversion do seem to have a common source, so retrocausality for a Bell experiment should work for paired photons using that method.

Austin

[Richard Gill]

Yes, entanglement is like classical correlation. It can be generated by post-selecting according to future events. There is no need for any physical interaction. Read Judea Pearl’s “Causality”.

Sent from my iPhone

On 23 Jun 2022, at 12:12, Austin Fearnley <ben...@hotmail.com> wrote:

Dear Richard

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[Алексей Никулов]

Dear Richard,

Schrodinger back in 1935 defined the EPR correlation as entanglement
of our knowledge: ”Maximal knowledge of a total system does not
necessarily include total knowledge of all its parts, not even when
these are fully separated from each other and at the moment are not
influencing each other at all” [1]. Anton Zeilinger was following in
understanding entanglement to Schrodinger [2]. But Zeilinger, in
contrast to Schrodinger, did not understand that a theory describing
our knowledge instead of reality cannot be considered a physical
theory. I write in the preprint “Logical proof of the absurdity of the
EPR correlation” about the fundamental different between classical and
quantum entanglement of our knowledge: our classical knowledge about
objects existing before our observation whereas our quantum knowledge
about objects which our mind creates at observation, see
https://www.researchgate.net/publication/331584709_Logical_proof_of_the_absurdity_of_the_EPR_correlation
.

[1] E. Schrodinger, Die gegenwartige Situation in der Quantenmechanik,
Naturwissenschaften 23, 807 (1935).
[2] Caslav Brukner, Marek Zukowski, Anton Zeilinger, The essence of
entanglement. ArXiv: quant-ph/0106119

With best wishes,
Alexey

чт, 23 июн. 2022 г. в 18:38, Richard Gill <gill...@gmail.com>:

> To view this discussion on the web visit https://groups.google.com/d/msgid/Bell_quantum_foundations/08960589-C239-452E-AEF4-C8F2B1B764CD%40gmail.com.

[Austin Fearnley]

Hi Richard

I am not yet ready to believe that generating a disattenuated correlation by post selection is a legitimate method.  One can also get the disattenuated correlation by missing data.  But data adjustments are IMO also iffy.  I need to work on beam splitters more to see what is happening .. but if there is no prior interaction or common source for a pair of particles then an S value even of say 2.67 is not conclusive of entanglement especially after data manipulation has taken place.

I looked at Pearl's 'Causality' last week.  But it is 300pp+.  I was sidetracked onto the Simpson's Paradox part.  Simpson's Paradox sometimes affected my work before retirement.  We used to have a one-side page summary explanation of the paradox. I once had to explain the paradox to a committee of arts folk as it affected their data. I said "surely you don't really expect me to explain a paradox to you!  After all, it is a paradox!  That got a laugh but I still had to try to explain it to them for their data.  It wasn't easy to deal with the problem.

Austin

[Richard Gill]

Andrey

You are again making dogmatic statements. I disagree with you. I think you misinterpret Schrödinger’s words. Maybe I have a different notion of “physical theory” to yours. I have the impression you are stuck with 19th century philosophical dogmas which the 20th century has needed to revise.

Your paper is entitled "Logical proof of the absurdity of the EPR correlation”. In a narrow sense this is a good title: you make some assumptions which I think are absurd (and they are certainly debatable), and deduce from them an absurd conclusion. 

Richard

[Алексей Никулов]

Dear Richard,

What assumptions in my paper "Logical proof of the absurdity of the
EPR correlation” do you consider absurd or debatable? Do you agree
that the expression for the EPR pair

EPR = (|A+B-> + |A-B+>)/2^{1/2} (1)

(1) in my paper can describe Alice's knowledge about the probability
of the results of observation by she and Bob both two balls of
different colors and spin projections of two particles with spin 1/2
in the EPR state? Alice's knowledge about the balls is entangled,
since she knows two balls of different colors, red and blue were in
the box. If Alice did not know that the balls are of different colors,
then her non- entangled knowledge could be described by the expression

NonEnt = (|A+> + |A->)/2^{1/2}(|B-> + |B+>)/2^{1/2} (2)

which is the product of two expressions describing Alice's knowledge
about each ball. Alice cannot learn the color of Bob's ball by
observing her ball when her knowledge is not entangled.

I draw your attention that the expression (2) can describe Alice's
knowledge about the observation results of spin projections only when
the spin projections are measured in the direction perpendicular to
the direction in which the spin state of this particle is eigenstate.
More generally, Alice's knowledge is described by the expression

NonEnt = (cos fA/2|A+> + sin fA/2|A->)(cos fB/2|B-> + cos fB/2|B+>)/2^{1/2} (3)

when she knows the angles fA and fB between the measurement direction
and the eigenstate direction of a particle A or B.

It surprises me that neither you nor others want to understand the
fundamental difference between observing balls of two colors and spin
projections. Alice will see a red ball with probability of 0.5 on the
first observation and probability of 1 on the second observation. In
this case, we can think that only Alice's knowledge has changed in
this case, since the ball was red before the first observation. But we
cannot think so in the case of observing spin projections, since
projections can be measured in different directions. Therefore, Dirac
and von Neumann had to postulate a change because of the observation
of not only the observer's knowledge, but also the quantum state.

The postulate of the jump of the system into an eigenstate of the
dynamical variable that is being measured under influence of the jump
in the observer's knowledge is obviously absurd. Believers in quantum
mechanics do not like to notice this absurdity. For this reason you
have the illusion that quantum mechanics is possible without the
collapse of the wave function. But without collapse, quantum
mechanics, according to Born's rule, would predict no less absurd
possibility of seeing one particle in several places at once. It is
the Born rule, that you believe in, that is the cause of the
inevitable absurdity of quantum mechanics.

With best wishes,
Alexey

пт, 24 июн. 2022 г. в 06:28, Richard Gill <gill...@gmail.com>:

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[Richard Gill]

Dear Alexey

I disagree.

The bipartite quantum state which you describe does not describe knowledge about balls of different colours allocated completely at random in closed boxes to Alice and Bob.

If you are talking about an experiment in which two balls are placed in closed boxes and sent (completely at random) one to Alice, and one to Bob, I would not use quantum mechanics to describe the experiment at all.

However, if I did, I would talk about an experiment in which the following is done: a third person (Carol) tosses a fair coin and either sends a spin up particle to Alice and a spin down particle to Bob (z-direction), or the other way round,

according to the fall of the coin.

Alice and Bob know Carol's procedure, the only thing they don’t know is the outcome of the coin toss. When they receive their particles they can measure them in the z direction. The result tells them the outcome of the coin toss,

And tells them what the other person has received.

I don’t know what you mean by in practical terms by “spin projections of two particles with spin 1/2”. 

If Alice and Bob didn’t know that the balls were of different colours then you haven’t told me enough to say anything yet. Boole in the 1850’s hoped that there would be a unique way to encode “complete lack of knowledge” in Bayesian probability terms, but failed. And later we know that he failed because there does not exist a sensible unique way to do this. There are many different ways depending on assuming some arbitrary convention but definitely not unique convention.

The state you write down for the second case is the case where Alice and Bob each get a pure quantum state of spin in at the same, definite direction, I think both in the y+ direction. Namely, the vectors (|A+> + |A->)/2^{1/2} and (|B-> + |B+>)/2^{1/2} are the same element of C^2. Notice that (|B-> + |B+>)/2^{1/2} = (|B+> + |B->)/2^{1/2}. Addition is commutative. The letters “A” and “B” are superfluous. The product of two elements of C^2. is an outer or tensor product.

[Richard Gill]

Austin, you are right to be suspicious of post-selection. The experiments which use entanglement swapping are three party Bell experiments. You have to think carefully about the spatio-temporal relations between inputs and outputs at three locations. 

Pearl’s magnum opus is unfortunately “magnum”. There are many much shorter books which popularise and specialise his work for different audiences. Epidemiologists; computer scientists; people working in algebra …

For instance:

https://journals.lww.com/epidem/abstract/1999/01000/causal_diagrams_for_epidemiologic_research.8.aspx

Richard

[Richard Gill]

PS, this is *not* “data manipulation”. Or “data adjustment”. There are three parties. We study the empirical probabilities p(x, y, z | a, b, c) and the conditional probabilities derived from them, p(x, y | z, a, b, c).

On Thursday, June 23, 2022 at 9:54:27 PM UTC+1 ben...@hotmail.com wrote:

[Алексей Никулов]

Dear Richard,

You seem to write that mathematics describes different objects in the
same way. No quantum state is in the mathematical expression

(|A+B-> + |A-B+>)/2^{1/2} (1)

I did not use quantum mechanics to describe Alice's knowledge about

the probability of the results of observation by she and Bob both two

balls of different colors. I tried to draw your attention that any
mathematical expression describing the probability of one of binary
outcomes should not depend on what is observed, for example, spin
projections or balls of different colors. The expresion (1) describes
the entangled knowledge about both two balls of different colors and
two particles with spin 1/2 in the EPR state.

Mathematical expression describing the probability of one of binary
outcomes should not depend on what is observed not only in the case of
two particles but any number of particles. I state that nothing
quantum is in the mathematical expression for quantum register. This
mathematical expression describes in the same way the probability of
one of binary outcomes both in case the observation of particles with
spin 1/2 and, for example, Schrodinger’s cats. This universality of
mathematics is the essence of my logical argument against almost
universal belief in the possibility of a quantum computer. This
argument reveals that the instrumentalist view is misleading.

The idea of a quantum computer is connected with the remark made by
Richard Feynman and Yuri Manin forty years ago that the complexity of
computing quantum systems increases exponentially with the number of
elements. Feynman and Manin have not understood that the exponential
increase of the complexity takes place not because the system is
quantum, but because the probability of observation is calculated.

Your example with a third person (Carol) allows us to understand the
fundamental difference between the observation of two balls of
different colors and particles with spin 1/2. In your experiment a

third person (Carol) tosses a fair coin and either sends a spin up
particle to Alice and a spin down particle to Bob (z-direction), or

the other way round, according to the fall of the coin. But this
experiment cannot be possible because neither a spin up particle nor a
spin down particle exist in the EPR state (1) before the first
observation of one of the particles. The expression for the EPR pair
(1) prediсts that the first measurement of one of the particles in any
direction will give spin up and spin down with equal probability 0.5.

Carol can use a fair coin only if she will be sending Alice and Bob
balls of different colors, for example red and blue. You wrote: “Alice

and Bob know Carol's procedure, the only thing they don’t know is the
outcome of the coin toss. When they receive their particles they can
measure them in the z direction. The result tells them the outcome of

the coin toss. And tells them what the other person has received”. You
have not taken into account that the z direction can be different, for
example, vertical or horizontal. You have not taken into account
exactly what I am trying to explain very popularly with the help of
Fig.1 in the preprint “Logical proof of the absurdity of the EPR
correlation”.

We can label red the observation spin up and blue - spin down when the
spin projection is measured along the z-axis directed vertically. But
Alice and Bob can measure the spin projections along the z-axis
directed horizontally and in any other direction. The essence of the
EPR experiment can be understood using the following analogy: Carol
sends Alice and Bob two balls that have no color before the first
observation, and the color of both balls is created by the observer
who is the first to see his ball.

With best wishes,
Alexey

сб, 25 июн. 2022 г. в 11:07, Richard Gill <gill...@gmail.com>:

> To view this discussion on the web visit https://groups.google.com/d/msgid/Bell_quantum_foundations/66cf725f-65c1-4f23-b445-4dffccbea486n%40googlegroups.com.

[Richard Gill]

Alexey, if you are not using QM formalism in your bra and ket notation, you had better tell me what your notation means.

I am not going to waste my time guessing.

Sent from my iPhone

[Mark Hadley]

Dear Alexey,

If you think that quantum computers will not work as predicted, then pick one of the proposals and do your own alternative calculations. Publish on Archiv. 

You will get a Nobel prize when you are shown to be right.

Nothing matters more than confirmed predictions. 

Cheers

Mark

[Richard Gill]

Alexey

Why do you say that the experiment I described is impossible? I did not mention the EPR state. I was not talking about the EPR state

In the experiment I described, any measurement by Alice in a direction in the x-y plane will give a completely random outcome. And similarly for Bob. And the outcomes given the settings will be statistically independent.

Richard

On 25 Jun 2022, at 22:46, Алексей Никулов <nikulo...@gmail.com> wrote:

[Алексей Никулов]

Dear Richard,

The notation, for example, |A+> may mean we observe that a ball A is
red, a particle A is deflected upward, an atom A is not decayed, a cat
A is live and any other one of any binary outcomes. We can denote the
atom as A, and Schrodinger's cat as B. Then Schrodinger's thought
experiment with a cat can be described by an expression

cat = a|A+B+> + b|A-B-> (1)

in which the observer's knowledge of the atom and the cat are
entangled. Here |a|^2 is the probability that the atom is not decayed
A+ and the cat is live B+ and |b|^2 is the probability that the atom
is decayed A- and the cat is dead B-.

The experiment with Carol you described is impossible according to
quantum mechanics. You wrote: a third person (Carol) tosses a fair

coin and either sends a spin up particle to Alice and a spin down
particle to Bob (z-direction), or the other way round, according to

the fall of the coin. According to what you wrote a spin up and spin
down along a z-direction exist before the observation. But this
assumption is not correct according to quantum mechanics even for
non-entangled spin states.

Even a reason to observe spin up and spin down is absent before the
observation according to quantum mechanics. Bell wrote in “Bertlmann’s
socks” “that atomic and subatomic particles do not have any definite
properties in advance of observation. There is nothing, that is to
say, in the particles approaching the magnet, to distinguish those
subsequently deflected up from those subsequently deflected down.
Indeed even the particles are not really there”. The theory of hidden
variables differs from quantum mechanics precisely in that, according
to this theory, in the particles approaching the magnet, there is a
variable by which, prior to observation, it is possible to distinguish
those that subsequently deflected up from those subsequently deflected
down.

With best wishes,
Alexey

вс, 26 июн. 2022 г. в 19:14, Richard Gill <gill...@gmail.com>:

[Алексей Никулов]

Dear Mark,

Not only do I understand that quantum computers will not work as
predicted, but I am surprised that such a false idea could not only
appear, but also become so popular. I consider the idea of quantum
computing, as well as the refutation of realism, to be a sign of a
crisis in physics, as a consequence of the degradation of physical
thinking because of the rejection of realism by the creators of
quantum mechanics.

I have written several times that the inability of our reason to
describe realistically some observed phenomena, for example the
Stern-Gerlach effect or the violation of Bell inequalities, indicates
only the inability of our reason, and not the absence of reality, and
even more so the possibility of creating a real device based on
evidence of the absence of reality. I don't think one can get the
Nobel Prize for proving the limitations of our reason in the cognition
of Nature.

“Nothing matters more than confirmed predictions” according to the
instrumentalist view which is misleading. The instrumentalist view has
misled Richard Feynman and Yuri Manin who have not understood that the
exponential increasing of the complexity takes place not because the

system is quantum, but because the probability of observation is

calculated. The idea of quantum computing has become popular because
most scientists who are naive realists did not understand that quantum
mechanics can be valid only according to the instrumentalist view.

With best wishes,

Alexey

вс, 26 июн. 2022 г. в 23:00, Алексей Никулов <nikulo...@gmail.com>:

[Jan-Åke Larsson]

On sön, 2022-06-26 at 23:00 +0300, Алексей Никулов wrote:

The experiment with Carol you described is impossible according to

quantum mechanics. You wrote: a third person (Carol) tosses a fair

coin and either sends a spin up particle to Alice and a spin down

particle to Bob (z-direction), or the other way round, according to

the fall of the coin. According to what you wrote a spin up and spin

down along a z-direction exist before the observation. But this

assumption is not correct according to quantum mechanics even for

non-entangled spin states.

Wrong. This experiment is perfectly possible within standard quantum mechanics.

Best regards
Jan-Åke

[Mark Hadley]

If you think a quantum computer will not work as predicted, then make your own specific predictions about a specific experiment. Don't just use emotional language about unspecified experiments. Make a statement that is precise enough to be tested. 

You misunderstand me about confirmed predictions. I don't mean that's all that is important. I mean that as a test between two theories, confirmed predictions will take priority over any philosophy etc. 

I am certain that if anyone makes a testable prediction that is contrary to the predictions of QM, then they will get a Nobel prize if they are correct. 

EPR has a long history. It was first proposed by Einstein et al to show that QM was an absurd theory. But being scientists they did not say absurd, but used the word incomplete. They assumed locality to reach the conclusion. 

I hope you can find more scientific language and make some testable predictions. 

Mark

[Richard Gill]

Actually I have argued the same thing, on the basis of fairly established findings in neuro-linguistics and developmental psychology: the theory of “systems of core knowledge”

https://www.aaas.org/look-core-knowledge-systems

Spelke and Kinzler 2007

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-7687.2007.00569.x

We are congenitally unable to accept irreducible randomness. We *know* that everything is ultimately caused by an agent, and actually, we *know* that agents can act across space, essentially instantaneously. There are always Gods, devils, or angels behind everything. We prefer to accept action at a distance than to accept pure chance. This is soft-wired into our brains, by evolution, as very social apes.

[Austin Fearnley]

Dear Richard

I have slowed down in my work explaining entanglement swapping via retrocausality and preon structure of photons and involvement of third party Charlie.  (My garden needs me and the summer warmth is only here temporarily.) I became bogged down in Weihs and Zeilinger (Figure 1.16) in https://copilot.caltech.edu/documents/16791/weihs_zeillinger_photon_statistics_at_beamsplitters_qip.pdf

'Bogged down' is fine as it makes one think more. Fig. 1.16 has entangled particles in a W shape. Entangled particles 1&2 from one source and entangled particles 3&4 from another source.  Particles 2&3 are then measured in a Bell measurement on a pair.  (Presumably both 2 & 3 measured at the same detector setting, which is not IMO a normal Bell measurement?)  If one can show that 2&3 are entangled, then particles 1&4 are deduced also to be entangled.  Fine.

But if there is a retrocausal link from particle 1 to particle 4, then there is no retrocausal link from 4 to 1. (The same applies in a two detector set up without Charlie.)  I had assumed until now that only tweaking the retro particle could make the other one jump.  But, if past particle paths still exist in a block universe then maybe that interlocked block structure can impose change either way in time. Maybe...

Chantal's point a while ago on retrocausality changing our past in unlimited scope is relevant.  But do we know that our past is forever fixed in an immutable block universe.  Is the block universe mutating?  Would that be a source of randomness.

Austin

[Austin Fearnley]

Not sure what 'irreducible randomness' is, but randomness is very important to the universe, of course.  Penrose's Cyclic Conformal Cosmology (CCC) model has the universe's spacetime ending at nodes in a cycle.  To end the spacetime structure of the universe may correspond to a complete lack of randomness in the universe.  Without the randomness, the spacetime cannot be maintained.  I have a paper:
Pseudo-Random Data Testing The Scales Used In Rasch Pairs Analysis/ Adaptive Comparative Judgement, at https://vixra.org/abs/1609.0329
This paper was written for a completely different purpose in trying to see whether the inherent objectivity of Rasch measurements should add to the interpretation of results based on those measurements.  Or should one simply use traditional methods of statistical analysis on the Rasch measurements.

Anyway, for current purposes, the paper shows that increased randomness in measurement makes the Rasch scale of results more compressed.  Applying this idea to the construction of the universe's space metric, I think this maybe shows that the randomness was greater when the universe was smaller, at an earlier stage.  The paper also shows that when the randomness is too small, the ability to make a Rasch scale breaks down.  The construction of a scale is undermined due to lack of randomness.  These ideas apply to scales in general and not merely to Rasch. A scale with not enough randomness is more generally called a Guttman scale.  I suspect that one of the more difficult parts of CCC to believe, in general, is the collapse of the spacetime metric at a CCC node.  Whereas for me it is very believable and the most interesting part.  

Now the following may be a contradiction but I do not believe randomness is the fundamental cause of spontaneous alpha decay, nor escape from potential wells.

Best wishes


Austin

[Алексей Никулов]

Dear Jan-Åke,

Einstein, explaining his negative attitude to quantum mechanics, was
saying: ”I like to think that the moon is there even if I don’t look
at it”. Heisenberg determined this Einstein’s position as dogmatic
realism: “When Einstein has criticised quantum theory he has done so
from the basis of dogmatic realism” [1]. Dogmatic realism is not an
extreme form of delusion according to Heisenberg: ”Metaphysical
realism goes one step further than dogmatic realism by saying that
’the things really exist’. This is in fact what Descartes tried to
prove by the argument that ’God cannot have deceived us’” [1].

I don't think that many scientists can seriously doubt that ’things
really exist'. The rejection of realism by Heisenberg and other
creators of quantum mechanics led to the degradation of physical
thinking and the illusion of reality of a quantum computer primarily
because almost all scientists are naive realists following
metaphysical realism. Even those scientists who refute realism are
sure that the moon exists when no one sees it, and not only the moon.
Carol can send a spin up particle to Alice and a spin down particle to
Bob (z-direction) only if such things as a spin up particle and a spin
down particle really exist before Alice and Bob will observe these
particles.

I would advise you to carefully read the excellent explanation of the
essence of the paradox of the Stern-Gerlach effect at the beginning of
the article “Bertlmann’s socks” and try to understand why Bell wrote:
“Phenomena of this kind made physicists despair of finding any
consistent space-time picture of what goes on on the atomic and
subatomic scale. Making a virtue of necessity, and influenced by
positivistic and instrumentalist philosophies, many came to hold not
only that it is difficult to find a coherent picture but that it is
wrong to look for one- if not actually immoral then certainly
unprofessional. Going further still, some asserted that atomic and

subatomic particles do not have any definite properties in advance of
observation. There is nothing, that is to say, in the particles
approaching the magnet, to distinguish those subsequently deflected up
from those subsequently deflected down. Indeed even the particles are
not really there”.

[1] W. Heisenberg, Physics and Philosophy. George Allen and Unwin Edition, 1959.

With best wishes,
Alexey

пн, 27 июн. 2022 г. в 11:07, Austin Fearnley <ben...@hotmail.com>:

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[Richard Gill]

Dear Alexey

I am sure that no-one is this group doubts that “things really exist”. 

When scientists talk about sending a spin-up particle to Alice and a spin-down particle to Bob, they mean that they follow an objectively described experimental preparation, that is highly reproducible, and which is such that the results of measuring whatever it is that is sent correspond to the QM predictions which everyone here is familiar with.

It doesn’t matter what words people use to say what they are doing, as long as everyone agrees on what those words are intended to imply.

You are attacking some kind of short-hand in speech. You misunderstand the jargon used by a certain group of physicists, and deduce from your misunderstanding that all of modern science is in crisis. 

One of the oldest pieces of writing in existence is a letter sent on a clay tablet from one Sumerian civil servant to another. He complained that the young people of his day didn’t know how to talk correctly, and he felt that civilisation as he knew it was in terrible decline.

Richard

[Алексей Никулов]

Dear Mark,

You wrote: “I mean that as a test between two theories, confirmed
predictions will take priority over any philosophy etc”. But such a
test makes sense only if two theories exist. But we don't have even
one theory of quantum phenomena. No theory can describe, for example,
even the Stern-Gerlach effect. Any specific predictions about a
specific experiment can be made only on the basis of a theory and such
predictions cannot be made if no theory exists.

I don't think it makes sense to make a testable prediction that is
contrary to the predictions of QM, but I drew attention six years ago
in the paper [1] on experimental results that are contrary to the
predictions of QM. No one wants to notice experimental results that
contradict quantum mechanics, which for most scientists is a religion
that they believe in, and not a scientific theory that they
understand.

EPR has a long history because of the inability of most scientists to
think logically. If most scientists could understand what Einstein
tried to explain in 1926 and 1927 immediately after Heisenberg's
proposal to describe the observed instead of the existing one and
Born's proposal to describe the probability of observation, then this
long history would simply not exist.

[1] Alexey Nikulov, Could ordinary quantum mechanics be just fine for
all practical purposes? Quantum Studies: Mathematics and Foundations,
V. 3, pp 41-55 (2016)

With best wishes,
Alexey

пн, 27 июн. 2022 г. в 17:29, Richard Gill <gill...@gmail.com>:

[Алексей Никулов]

Dear Richard,

I am also sure that no-one in this group can really doubt that “things
really exist”. Most scientists follow metaphysical realism rather than
dogmatic realism, unlike Einstein. I write in my unpublished article
“Physical thinking and the GHZ theorem” that Einstein followed
dogmatic rather than metaphysical realism since he was understanding
the validity of Kant’s avowal that ”it always remains a scandal of
philosophy and universal human reason that the existence of things
outside us (from which we after all get the whole matter for our
cognitions, even for our inner sense) should have to be assumed merely
on faith, and that if it occurs to anyone to doubt it, we should be
unable to answer him with a satisfactory proof”.

According to Kant’s philosophy realism is the regulative principle of
our reason, which determines the very possibility of empirical
cognition of Nature. It is easy to understand without philosophy why
realism determines the very possibility of empirical cognition.
Realism (dogmatic according to Heisenberg) states that the moon exists
even if no one looks at it. Therefore, we must explain how our mind
creates the moon when observing if we reject realism. Einstein, like
Kant, understood that realism is ”the presupposition of every kind of
physical thinking” rather than a claim which can be disproved with any
experimental results. The creators of quantum mechanics abandoned
realism because of the impossibility of a realistic description of
some quantum phenomena. This rejection was a fundamental mistake since
the rejection of realism results in the degradation of physical
thinking.

The degradation of physical thinking is manifested in the uncertainty
and inconsistency of statements not only by modern authors, but even
by the creators of quantum mechanics. A certain group of physicists
misunderstand the jargon which they use. In particular they do not
understand why variables can be hidden. You have expressed doubt that
the theory of hidden variables can be distinguished from quantum
mechanics. But we are talking about theories created by our (human)
reason, and not about reality or phenomena that we did not create.
Therefore, we must clearly understand the essence of the difference
between the theory of hidden variables and quantum mechanics and the
logical consequences of this difference.

Hidden variables play the same role as the thing-in-itself in Kant's
philosophy: they are the cause of the phenomena which we observe. Kant
understood that without the thing-in-itself the mind of the observer
should logically become the cause of the phenomena. Einstein also
understood that the denial by the creators of quantum mechanics of the
cause of some quantum phenomena in Nature, makes the mind of the
observer the cause of these phenomena. Quantum mechanics indeed
postulates that the mind of the observer can create quantum states at
observation.

A certain group of physicists and not only physicists do not quite
clearly understand that there is a method of description and the
subject of description. You did not recommend me to use ket’s to
denote observational facts, when everyone else is used to using them
to denote vectors in Hilbert space. But vectors in Hilbert space refer
to the description method used in quantum mechanics to describe the
observer's knowledge of the results of an upcoming observation, which
are the object of description in this case.

I draw your attention that quantum mechanics uses not only Hilbert
space, but also real three-dimensional space to describe quantum
states. It is this subjective and objective consideration of quantum
states that is one of the reasons for the mass illusion about the
reality of a quantum computer in real three-dimensional space.
According to almost universal opinion, the advantage of a quantum
computer is based on the fact that “Hilbert space is indeed a big
place” [1]. But a quantum computer must exist in the real
three-dimensional space rather than multidimensional Hilbert space.

You think David Deutsch and other proponents of Many Worlds are idiots
because you don't understand that orthodox quantum mechanics is more
contradictory, more absurd and more misleading than the theory of Many
Worlds. I think one can say the same thing about David Deutsch that
Einstein said about Louis de Broglie: he seems crazy, but he thinks
very logically.

[1] M. A. Nielsen and I, L Chuang, Quantum Computation and Quantum
Information. Cambridge University Press, 2000.

With best wishes,
Alexey

пн, 27 июн. 2022 г. в 17:42, Алексей Никулов <nikulo...@gmail.com>:

[Mark Hadley]

Sadly, you are making up your own language. We all use the term "quantum theory" to refer to the theory that makes successful predictions about the quantum world. That's what Richard myself and millions of scientists use to make successful predictions.

If you have a different theory that makes contrary predictions, as you claim for quantum computers, then publish those predictions. The early experiments are being done now. 

Be aware that there are very powerful no go theorems which constrain other probability structures and alternative equations.

Unless you can add some specifics, then it's not much more than poetry. I say that with the utmost respect, because I am also failing to make testable predictions for my work. 

You don't need to keep telling us that quantum theory fails to explain nature. We know that. Some of us care, some don't care, some do care but think it's too hard to solve. 

By the way, Einstein made many mistakes. His views are always interesting from a hystorical perspective, but they prove nothing.

I don't see the claims for quantum computing as particularly remarkable. They will be good at solving some problems, bad at others. Is it much different to comparing analogue computers with digital ones?

Cheers

Mark

[Mark Hadley]

Dear Alexey,

Sorry, but many worlds interpretation does not make any predictions contrary to quantum theory. And that includes quantum computers. I wish it did because then we could do the experiments and relegate the theory to its proper place.

Using higher dimensional hilbert spaces to do calculations, does not seem any more odd than engineers using complex numbers and fourier transforms up do calculations for electric circuits. 

Cheers

Mark

[GeraldoAlexandreBarbosa]

"I am also sure that no-one in this group can really doubt that “things really exists ..."

It depends on what you understand by "existence". In my view, what you call "it exists" it is just your sensorial perception (whatever that means) trying to model "signals received" within a context that helps you to live. The question "modeling what?", is beyond our capacity to understand ... but we can develop beautiful models and good predictions about signals.

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[Алексей Никулов]

Dear Geraldo,

As I understand, you follow the philosophy of subjective idealism of
George Berkeley, one of representatives for early empiristic
philosophy, who stated that "to be is to be perceived". Quantum
mechanics largely follows the empiristic philosophy although
Heisenberg knew that empiricism leads to scepticism about the
possibility of empirical cognition. He said in 1956 in his lectures
``Physics and Philosophy”: “The three philosophers who can be taken as
representatives for early empiristic philosophy are Locke, Berkeley
and Hume. Locke holds, contrary to Descartes, that all knowledge is
ultimately founded in experience. This experience may be sensation or
perception of the operation of our own mind. Knowledge, so Locke
states, is the perception of the agreement or disagreement of two
ideas. The next step was taken by Berkeley. If actually all our
knowledge is derived from perception, there is no meaning in the
statement that the things really exist; because if the perception is
given it cannot possibly make any difference whether the things exist
or do not exist. Therefore, to be perceived is identical with
existence. This line of argument then was extended to an extreme
scepticism by Hume, who denied induction and causation and thereby
arrived at a conclusion which if taken seriously would destroy the
basis of all empirical science”.

Heisenberg misled several generations of physicists precisely because
he did not take the extreme scepticism of Hume seriously. He did not
understand that empirical sciences are possible only according to the
philosophy of Kant, who agreed with Hume that we cannot state that
induction and causation are in Nature as in thing-in-itself, since we
cannot know anything about a thing-in-itself. The laws of induction
and causation relate to our ideas about Nature, being a condition of
its cognizability. Realism, which states that things really exist, is
also a condition of the cognizability of Nature. I wrote already that
according to Kant’s philosophy realism is the regulative principle of

our reason, which determines the very possibility of empirical
cognition of Nature. It is easy to understand without philosophy why
realism determines the very possibility of empirical cognition.

Realism states that the moon exists even if no one looks at it.

Therefore, we must explain how our mind creates the moon when
observing if we reject realism. Einstein, like Kant, understood that

realism is ”the presupposition of every kind of physical thinking”. I
agree with Kant and Einstein but not with Berkeley and Heisenberg.

[1] W. Heisenberg, Physics and Philosophy. George Allen and Unwin Edition, 1959.

With best wishes,
Alexey

вт, 28 июн. 2022 г. в 01:33, GeraldoAlexandreBarbosa
<geraldo...@gmail.com>:

[Алексей Никулов]

Dear Mark,

You and millions of scientists are constantly confusing predictions of
experimental results with predictions about the quantum world. This
misunderstanding of the difference between instrumentalism and realism
is the main reason for the illusion of you and millions of scientists
about the reality of a quantum computer. If you know that quantum
theory fails to explain nature you must understand that quantum theory
is a trick that is misleading rather than a scientific theory.

With best wishes,
Alexey

вт, 28 июн. 2022 г. в 20:59, Алексей Никулов <nikulo...@gmail.com>:

[Mark Hadley]

On Tue, 28 Jun 2022, 19:27 Алексей Никулов, <nikulo...@gmail.com> wrote:

Dear Mark,

You and millions of scientists are constantly confusing predictions of
experimental results with predictions about the quantum world.

I don't see how you could have a prediction about the quatum world that is not a prefiction about an experimental result. Perhaps if you give an example. 

This
misunderstanding of the difference between instrumentalism and realism

You make insulting statements. I know perfectly well the difference between instrumentalist, realism and pragmatism. I used to teach this without advocating one or the other. 

is the main reason for the illusion of you and millions of scientists
about the reality of a quantum computer.

In reality a quatum computer will be a real physical experiment, conducted in real 3+1D space, the outcomes of which are predicted by quantum theory. 

If you make alternative predictions about the operational results of a quatum computer, then tell us. 

If you know that quantum
theory fails to explain nature you must understand that quantum theory
is a trick that is misleading rather than a scientific theory.

I also find quantum theory deeply unsatisfactory, but don't dismiss the successes. It explained the pattern of the periodic table and atomic spectra. And that's just to start. 

Cheers

Mark

[Алексей Никулов]

Dear Mark,
All predictions about the world (our idea about reality) are based on
predictions about experimental results. But predictions about
experimental results (our observations) are not always predictions
about the real world. The Ptolemaic system predicts the position of
stars and planets in the sky, but this does not mean that it says
something about the real world. You claim that you know perfectly well
the difference between instrumentalist view and realism. But you
obviously do not understand that, no fundamental difference is between
the Ptolemaic system and the Copernican system according to the purely
instrumentalist view, at least no difference was in the time of
Galileo, since both systems successfully described the results of
observations known in that time. The difference can exist only
according to the realist view which Karl Popper called the Galilean
tradition.

You also apparently don't know or don't understand, in contrast to
Karl Popper, that Heisenberg, Bohr and other creators of quantum
mechanics broke with the Galilean tradition and followed the
instrumentalist point of view of Cardinal Bellarmino and Bishop
Berkeley. You apparently don't understand, in contrast to David
Deutsch, that only the Galilean tradition, i.e. the realist view, led
to space flights, which would hardly have been possible if the
instrumentalist point of view had won. Deutsch was right when he
stated that a real device, for example, an interstellar spaceship
cannot be made on the basis of a theory which only predicts the
outcomes of experiments as the Ptolemaic system and quantum mechanics
make.

Millions of scientists believe in the possibility of creating a
quantum computer, not because they are instrumentalists, but because
they are naive realists. The authors of the book [1] are sure that the
Stern-Gerlach experiment [2] gives evidence of the real existence of
qubits in Nature. The extreme degree of naivety of the authors of the
well-known book about quantum computing should be understood by those
who know that Einstein and Ehrenfest drew attention to the complexity
of realistic description of the Stern-Gerlach effect just after its
discovery in 1922 [3] and those who understand Bell's excellent
explanation in the beginning of “Bertlmann’s socks” [4] of the reason
for the impossibility of the realistic (i.e., as a manifestation of
Nature) explanation of the observation only discrete values of
projections of atom magnetic moments.

Millions of scientists, like you, believe in quantum mechanics because
of its successes. Most people have always believed in miracles more
than in logical arguments. The worst thing is that now most scientific
journals are dominated by censorship of believers in the wonders of
quantum mechanics. The editors of most journals do not want to
understand that the rejection of realism by the creators of quantum
mechanics led to the degradation of physical thinking.

[1] M. A. Nielsen and I. L. Chuang, Quantum Computation and Quantum
Information. Cambridge University Press, (2000)
[2] W. Gerlach and O. Stern, Das magnetische Moment des Silberatoms.
Zs. Phys. 9, 353-355 (1922).
[3] A. Einstein and P. Ehrenfest, Quantentheoretische Bemerkungen zum
Experiment von Stern und Gerlach. Zs. Phys. 11, 31-34 (1922).
[4] J. S. Bell, Bertlmann’s socks and the nature of reality. Journal
de Physique 42, 41 (1981).

With best wishes,
Alexey

вт, 28 июн. 2022 г. в 23:32, Mark Hadley <sunshine...@googlemail.com>:

[Mark Hadley]

Again you make totally false completely unnecessary insults:

  "But you

obviously do not understand that, no fundamental difference is between

the Ptolemaic system and the Copernican system... " 

You are not addressing reasonable questions that are asked. 

I'll end the conversation now. 

Cheers

Mark

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