papers.html

Papers

Previously, the entries on this page were arranged with the earliest entries first. But as the page got longer,
I decided that it would be easier to read if the entries were arranged blog-style, with latest first.
Since the earlier entries are so few, and I don't remember when they were written, I haven't bothered to date them.

November 25, 2012: Possible errors in "A derivation of quantum theory from
    physical requirements" by Lluis Masanes and Marcus P. Mueller

    The July 1 entry below discussed several recent attempts to "derive" finite dimensional quantum
mechanics from physical principles. One of the simplest and most clearly written was the paper
of Masanes and Mueller mentioned in the title for this entry, arXiv:1004.1483v4 ,
New J. Phys. 131: 063001 (2011).

    My attention was very recently directed to this work, and I began to read it seriously. It is unusually
clearly written, and much easier to penetrate than some of the other attempts mentioned in the July 1
entry. I was saddened to find what looks like an essential error in Theorem 2, a key result on which
the rest of the paper is based. The technical details can be found in the linked "Comment" paper.
[Note: It has been unlinked and replaced with a corrected "Comment" ; cf. December 6 Update
below.]

    Almost two weeks ago, I sent a preliminary version of the "Comment" to the authors. There was
a brief acknowledgement from Dr. Masanes, but no substantive reaction to its analysis.

    A few days ago, I sent a later draft (which differs only cosmetically from the linked version above) to
Dr. Masanes with an offer to withhold it from circulation if he thought there might be anything wrong with it,
until any differences of opinion could be resolved. There was no response. Emails to Dr. Mueller
have bounced, and I have been unable to contact him.

    Normally, I would wait longer before making the "Comment" public because I am acutely aware of the
possibility that I might have misinterpreted the proof of Theorem 2, and I have no wish to muddy the waters.
However, it looks as if personal circumstances may prevent me from dealing with this matter for an indefinite
period, so I thought I had better post it now. If it turns out that it is in error, I apologize in advance both to the
readers and authors.

[Update December 6, 2012: After the above was posted, Dr. Masanes convinced me that the
conclusion of Theorem 2 is correct, though I still think that the published proof is not clear. Rather than
withdraw the "Comment" paper, I have replaced it with a CorrectedComment , which is identical to the
original except that a proof of Theorem 2 has been added. This new proof follows explanations of
Dr. Masanes. I fleshed in the details, and am responsible for any errors. ]

November 23, 2012: End of Journal of Physics A experience (?)

The September 2, 2012 entry described how two "Comment" papers submitted
over eight months previously to the Journal of Physics A (JPA) were still in limbo,
and how I had given up hope that they would ever be properly considered.

These ''Comments" commented on J. Dressel, J., and A. N. Jordan, "Sufficient conditions
for uniqueness of the Weak Value", J. Phys. A: Math. Theor. 45 015304 (2012).
This paper will be called DJ below.

On November 2, I received a rejection letter for both "Comment"s.

    The rejection letter included only a report from an unnamed member of the JPA's
Editorial Board, not a normal referee's report. Internal evidence suggested that
he probably hadn't read the longer "Comment" (which I shall call "Proof Gap") with any care.
The report didn't dispute anything in "Proof Gap", and didn't give any substantive
reason for the rejection. The only "reason" given was that rejection was the
"most satisfactory" course for JPA.

    On November 4, I sent JPA a lengthy letter pointing out several important issues
which the Board member's report had ignored. The letter also requested the referees'
reports.

    A week passed without a reply from JPA. On November 11, I sent them a brief note
stating that I could not guess whether they intended to ignore the issues raised by the letter,
but whatever the case, I would appreciate just the receipt of the referees' reports. If there
were anything wrong with the "Comment", I wanted to know. I thought that after waiting
almost a year for their decision, at least they should give me a reason more substantial than
that rejection was the "most satisfactory" course for them.

    After almost two weeks had passed without a reply to that, I assumed that they would
never reply. I was filled with regret for wasting so much time and effort on "Proof Gap",
in the naive belief that it would be seriously considered.

    I was surprised, almost shocked, to find today (November 23) in my inbox a message
from JPA. It admitted that there had been no referees' reports. They had sent "Proof Gap"
to a referee or referees who promised to deliver a report, but never did.
They said that they would discuss the issues raised by my November 4 letter and get back to me.

    I don't have any expectation that they will change their rejection decision, and I don't
particularly care because I am thoroughly disgusted by the whole matter.
However, I do appreciate the integrity of their admission that there were no referees' reports.
I had expected that to avoid admitting that, they would ignore all future inquiries. Perhaps
my expectations had been colored by Dressel and Jordan's systematic ignoring of requests
to clarify their published claims, and by the apparent acceptance of this "stonewall" tactic by
both Physical Review Letters and JPA.

    The Board member's report gave the impression that Dressel and Jordan had promised
to submit an erratum to DJ, an erratum which "will have to acknowledge that this correction
was prompted by Dr Parrott's criticism by quoting the arXiv version [of "Proof Gap"] " .
That would go a long way toward preventing readers of DJ from being misled. It shows
that JPA has at least some recognition of its professional obligation to correct errors
in what it publishes.

    However, I won't be holding my breath for the appearance of the erratum. That is the
sort of thing that could be easily deferred until "forgotten". For all their good intentions,
I doubt that JPA will keep on the heels of Dressel and Jordan. I'll believe it when I see it.

September 2, 2012: Standards of Journal of Physics A;
    comments on recent papers of Dressel, Agarwal, and Jordan on "contextual values"

In January, 2011, I became interested in a 2010 paper in Physical Review Letters (PRL)
by J. Dressel, S. Agarwal, and A. N. Jordan entitled "Contextual Values of
Observables in Quantum Measurements" (Phys. Rev. Lett. 104 240401 (2010),
http://arxiv.org/abs/0911.4474 . I found a counterexample to its main nontrivial claim and,
after the authors had begun systematically ignoring inquiries about this paper, posted it in
http://arxiv.org/abs/1105.4188.

    About five months later Dressel and Jordan (DJ) published an attempted refutation of
the counterexamples (by this time there were two because DJ added hypotheses to their
original claim in order to invalidate the first counterexample) in Journal of Physics A (JPA).
This paper was accepted about a month after submission, an unusually short time.

    I submitted two "Comment" papers to JPA, one very short and simple, and one longer at 6 pages.
Approaching nine months after their submission in December, 2011, JPA has still not decided what
to do with them. For the full story, which comments on the standards and practices of JPA and,
implicitly, on the "contextual value" papers of Dressel, Agarwal, and Jordan, click on GivingUpOnJPA .

August 18, 2012: Standards of Physical Review Letters

    Over a year ago, I had a lengthy experience giving insight into the standards of Physical Review Letters (PRL),
which is the self-proclaimed "world's foremost physics letters journal" (a quote from its website).
I have been meaning to make it into a journal entry but have put it off because the matter is so distasteful,
and also is not yet fully settled (though it is settled so far as PRL is concerned).

    In very brief summary, in 2010 PRL published a paper on quantum "weak measurement" which interested me enough to
carefully study. I questioned the main nontrivial claim of the paper and wrote the authors about it. They sent me
an attempted proof of the claim, but it was incorrect. I found a counterexample to the proof (but not to the claim itself)
and sent it to the authors. (The presentation of the counterexample was courteous, not confrontational.) They never
acknowledged it, and also ignored several subsequent inquiries about various aspects of their paper.

    After they did not respond to suggestions that they should correct their paper in an Erratum to prevent future readers
from being misled as I had, I submitted a Comment paper to PRL in late February, 2011. That began a kind of odyssey
which ended in the rejection of three versions before the final rejection of the fourth version in August, 2011. Some of these
versions presented a counterexample to the claim itself (not just to the attempted proof which the authors had sent me),
a counterexample which neither PRL nor its referees disputed.

    The bottom line is that it seems almost impossible to inject any genuine peer review into PRL. Based on this experience,
I have to conclude that PRL has almost no interest in correcting erroneous work which it has published. The lengthy and
convoluted details of my interactions with PRL can be found here .

July 2, 2012: A recent attempt to rule out "hidden variable" models of quantum mechanics

    ArXiv 1111.3328, to be published in Nature Phys. 3, 476 (2012), by M. Pusey, J. Barrett, and T. Rudolph (called PBR below) has attracted a lot of attention recently. Version 1 in the arXiv was entitled "The quantum state cannot be interpreted statistically", and though it has been superseded by Version 2 titled "On the reality of the quantum state", I first encountered Version 1 and so will start there.

    When I first came across Version 1, I didn't understand it, nor why it was arousing so much interest. I don't mean that I didn't understand its mathematics (which is simple and straightforward), but I didn't grasp its philosophical significance.

    Then I came across a blog of Matthew Leifer, http://mattleifer.info/2011/11/20/can-the-quantum-state-be-interpreted-statistically/, which sets forth its philosophical significance in an exceptionally clear way. This should really be considered an expository paper, and it deserves to be published, or at least posted in the arXiv.

    Leifer's explanatory blog has been cited in various published papers, and I think it was probably one of those that drew my attention to it. I recommend it to any reader before reading PBR.

    The second arXiv version of PBR (which the authors indicate will differ from the published version) adds explanation similar to Leifer's, but not as complete. Even with this additional explanation, I think that most readers will find PBR more comprehensible if they read Leifer's blog first.

    I hope it was only an oversight that the second version of PBR in May, 2012, did not reference Leifer's much cited November 20, 2011, blog.

    Regarding the substance of PBR, it basically rules out "hidden variable" models for quantum mechanics in a very general context. I have seen it interpreted as a more general version of Bell's theorem, which also rules out hidden variables, but I don't think this would be quite accurate. So far as I can see, PBR does not imply Bell's theorem. The two results start from different hypotheses. Bell's theorem essentially assumes "locality", that "information" cannot be transmitted faster than the speed of light, while PBR does not, so far as I can see. On the other hand, PBR seems to assume more of the structure of quantum mechanics than does Bell's theorem.

    This was pointed out by C. Blood, "A problem with the Pusey, Barrett, Rudolph analysis of the reality of the quantum state", http://arXiv.org//abs/1206.6491, in different language. He questions whether a particular projective measurement which the PBR argument requires is physically implementable. He does not claim that it is not implementable, only that it has not been proved that it is.

    Since the implementability of all projective measurements is part of the usual formulation of quantum mechanics, the PBR argument still shows that (under its hypotheses), the usual formulation cannot be derived from a hidden variable model. On the other hand, Blood's observation shows that it is conceivable that a slight weakening of the usual formulation might be consistent with a "hidden variable" (or "epistemic" in more current terminology) model.

       I have forgotten where I heard the remark to the effect that

            impossibility arguments mainly reveal a lack of imagination of their proponents,

but I have taken it seriously ever since I lost a bet many years ago. Someone had proposed the following problem:

Suppose we have 12 balls, of which 11 are identical and one "odd ball" is heavier or lighter than the rest (but we don't know which).
Given a balance scale, determine in no more than three weighings which is the "odd" ball.

I bet that it was impossible, and lost. My basic reasoning, slightly simplified, was that the first weighing would merely reduce the problem to one at least as hard as a 6-ball problem with two weighings left. Similarly, that problem would be reduced to a 3-ball problem with only one weighing allowed, which is clearly impossible. Essentially, I thought that binary search would be optimal, and binary search fails. I think that this kind of reasoning would probably survive scrutiny at most physics journals and many mathematics journals.

    The subtle solution to this puzzle still amazes me. Indeed, it took me about an hour to reconstruct it (the bet was lost about 50 years ago) even though I more or less remembered the trick.

    Whenever I see a purported proof of impossibility, I am reminded of my embarrassing loss of that bet. That is not to say that impossibility proofs have no value; they do because they point out where not to look for a solution. But I would think very hard before betting good money on the actual impossibility of a conclusion of an impossibility proof. There is always the possibility that some subtle, unstated hypothesis may invalidate the proof in practical situations.

    Before leaving the subject, I should make clear that I haven't checked PBR in complete detail, only one special case which they present first and gives the main idea of their proof. This special case is mathematically very simple, and their very clever argument shows a hidden variable model cannot account for this special case.

    I include this caveat because I generally try to avoid referencing works for which I cannot vouch in all essential aspects. (I am speaking generally here; I have no reason to doubt any aspect of PBR.) This is quite different from the custom of the physics literature of referencing all vaguely related work, presumably without implication of endorsement.

    I have assumed that my convention serves readers better, but I am in the process of rethinking this. It is no secret that the physics literature is generally unreliable (by comparison, a perceived order of magnitude less reliable than the mathematics literature). How should one deal with a paper whose results are relevant, but about which one has private doubts which one might be reluctant to express publicly? Reference it anyway? Or ignore it (which would be unethical according a strict reading of the guidelines of the American Physical Society)? If readers have any thoughts about this, I would be interested in hearing them.

July 1, 2012: Recent attempts to axiomatize quantum mechanics; unreliability of the physics literature

    It has been a long time since the last entry. I have been active, but have little to show for it. Last year I became interested in recent attempts to derive quantum mechanics from axioms based on information theory which some consider more intuitive than "usual" axiom systems such as those of von Neumann, Mackey, and Segal. Some of the papers that I attempted to read (in order of arXiv posting or publication, not order of reading) were:

    Hardy, L., "Quantum Theory From Five Reasonable Axioms", arXiv:0101012v4

    Barrett, J., "Information procession in generalized probabilistic theories",
        arXiv:0508211v3

    Masanes, L., and Muller, M., "A derivation of quantum theory from physical requirements", arXiv:1104.1483v4

    Chiribella, G., D'Ariano, G., and Perinotti, P., "Probabilistic theories with purification", Phys. Rev. A. 81, 062348 (2010), arXiv: arXiv:0908.1583,
         (called CDP10 below)

    Chiribella, G., D'Ariano, G., and Perinotti, P., "Informational derivation of quantum theory", Phys. Rev. A 84,012311 (2011), arXiv: arXiv:1011.6451
        (called CDP11 below)

All of these attempt to derive important parts of finite dimensional quantum theory from axioms which have "operational" meaning, i.e., which might in principle be tested in the laboratory, or at least have intuitive meaning. By comparison, Mackey's axiomatization of quantum mechanics rests on an axiom which can hardly be considered intuitive: that the partially ordered set of all questions which one can ask is isomorphic to the set of closed subspaces of a complex Hilbert space.

    The probable influence of the 2001 Hardy paper on the others is evident. It is written in a refreshingly simple style, with the physical situation very explicitly described. The other papers start with similar physical setups, but not so explicitly described. I suggest reading the introductory material in Hardy before attempting any of the other papers.

    However, I wasn't able to follow Hardy's mathematics in detail, despite considerable effort. Some of it is vague, and though presented in a deceptively simple style, it is logically quite complex. Many of the important arguments are relegated to appendices, where they are not presented in sufficient detail for me to follow.

    So far as I know, this paper was never published, and later Hardy posted a completely different attempt at axiomatiztion of quantum mechanics:

Hardy, L., "Foliable Operational Structures for General Probabilistic Theories", arXiv0912.4740 .

I have not attempted to read this later paper in detail. However, I would love to discuss the earlier 2001 paper with anyone who has (or is prepared to) read it in detail.

    The 2010 and 2011 Chiribella, et al., papers (called CDP10 and CDP11 below, and jointly CDP) have attracted a lot of attention. For example, they were chosen for discussion in the American Physical Society's expository journal "Physics": Brukner, C., Physics 4, 55 (2011). This can be obtained online without a subscription at http://physics.aps.org/articles/v4/55 .

    CDP11 is to some extent a continuation of CDP10. Both papers are long and intricately complicated. I don't mean just that a few key results have complicated proofs, but that the logical structure of the entire work is intricate. CDP10 is 40 pages with 64 definitions, 34 lemmas, 30 theorems, and 50 corollaries. CDP11 is 39 pages with 12 definitions, 78 lemmas, 20 theorems, and 51 corollaries.

    Here are excerpts from a partial review which I posted on the Internet newsgroup sci.physics.research. I was hoping (and still hope) to connect with someone interested with discussing these papers in detail, but that search was in vain. Nobody replied.

    There was an article about the CDP result in an expository science magazine which I shall not name in order to avoid identifying some people who were quoted in that article, but who expressed strikingly different views privately. Having failed to find anyone willing to discuss CDP through internet postings, I wrote to the people who were quoted by that science magazine as commenting favorably on the CDP. One of them intimated that he had been misquoted. All admitted that their knowledge of CDP was superficial. None had any interest in discussing the papers.

    I had identified what seemed to me to be some questionable points in CDP. Having failed to find anyone with any interest in analyzing CDP in detail, I finally wrote to Dr. Chiribella. I was extremely surprised to find in my inbox, the very next day, a four-page manuscript typeset with complicated mathematical notation, which satisfactorily resolved the points I had raised. It must have taken hours to produce!

    I went back to reading CDP, and found some more questionable points, which would have to be resolved before further reading would be productive. I again sent my questions to Dr. Chiribella. There was a short response that he was very busy at the moment but would answer them when he had time. That was over six months ago.

    I am sure that no discourtesy was intended. His initial response far exceeded what I expected, or what I would have had a right to expect. Because of that, I am reluctant to impose with further inquiries.

    In case anyone else is interested in CDP, I post here my unanswered second letter to Chiribella (Nov. 18, 2011) detailing what look to me like questionable points in CDP. It is too technical to be meaningful to anyone who is not actively reading CDP in detail, so if you're not in this category, there is no point to download it. I post it because it would seem a shame to let my work reading CDP vanish without a trace. Posting it is very little effort, and there is a long shot that it might conceivably help someone.

    Though it would have been a waste of time to have continued reading CDP without resolving these essential issues, I might continue if they were resolved, or even if I were relatively confident that they could be resolved, e.g, if CDP had been published in a seriously refereed journal.   CDP, which is essentially an intricate mathematical work, was published in Phys. Rev. A, which (like all the American Physical Society journals along with many others) is not known for its reliability. It is very conceivable to me that CDP has never been read with care by a referee nor indeed, by anyone other than its authors.

    This is a depressing situation. To put it into context, I will start a story which I intend to post in detail in a later entry.

    Over a year ago, I became interested in claims in a new paper in Phys. Rev. Letters concerning quantum "weak measurement". It was full of what I later recognized as "hype", and partly because of that I initially didn't realize that its claims were only claims, not based on competent research, and essentially unexamined by competent referees. The paper omitted so much non-standard information essential to understand it and contained such grievous and elementary mathematical errors that it is inconceivable to me that the referee could have read it with any care. It should never have been published in anything close to its present form. (I do not say that it should never have been published at all.)

    I wrote the authors with several questions about it, and they sent me a purported proof of its main claim. It was incorrect. I found a counterexample to the proof, though not to the claim. I sent the counterexample to the authors, but they did not reply, nor did they reply to subsequent correspondence. (It later became clear that they were deliberately ignoring these inquiries.) They also did not issue any kind of retraction or correction of the claim.

    Later I found a counterexample to the claim itself (not just to the attempted proof that they had sent me). That set off a year-long effort to correct the claim in the literature, an effort which has still not reached final resolution, and so far has involved something like a hundred pages of correspondence. Had I realized the extent of the effort, I might well have never undertaken it. However, once substantial work has been invested, there is always the mirage that a little more might finish the matter.

A Comment paper which I submitted to J. Phys. A , which published one of their incorrect proofs, has been in consideration for over half a year, which may mean that it has never been read carefully and may never be read. By comparison, the same journal accepted the authors' incorrect proof almost immediately (about a month after submission), despite the fact that they were well aware that it had been challenged. An offer to discuss my objections to the proof with the referee before publication was ignored.

    That is a bare outline of that situation. I intend to fill in the details (which are lengthy and quite bizarre) in a later entry. The point of mentioning it now is to emphasize that mere publication of a claimed result in a supposedly reputable physics journal does not imply that the claim has undergone serious peer review. I am convinced that papers of a certain complexity by authors with appropriate credentials are routinely recommended for publication simply because it would take referees too much time to analyze them in detail. Even when later found to be wrong, they are rarely corrected or withdrawn.

    The mathematics refuting the claims of that Phys. Rev. Lett. paper is relatively simple and, I believe, virtually unquestionable. If there is so much difficulty correcting those claims, imagine the difficulty of locating and reporting errors in CDP, a work which is orders of magnitude (maybe 1000 times) more intricate. Imagine the investment in time necessary to understand CDP, with the real possibility that in the end, important parts of it might turn out to be in error.

    That is why the situation seems so depressing. Papers like CDP are often published without meaningful review and most likely never read carefully by anyone (other than the authors). One has to make value judgments on limited information about how to invest one's limited time. Much as I would like to understand CDP, I have reluctantly decided that the expected value of this investment would be too low.

    There is an old physicists' joke which goes something like the following:

   "The journals of the APS are expanding on library shelves faster than the speed of
    light, but this does not contradict the theory of relativity because no information
    is being conveyed."

This is mildly amusing because, though distorted, there is more than a grain of truth in it.

November 28, 2010

I have mixed feelings about Wikipedia. I consult it a lot, but always with reservations. I've found many articles on strictly mathematical subjects helpful and reasonably accurate, but articles on physics seem much more uneven. I thought the article on quantum weak measurements, http://en.wikipedia.org/wiki/Weak_Measurement , was particularly misleading, and in some ways just plain wrong. That is where I came across the link to the Discover magazine article http://discovermagazine.com/2010/apr/01-back-from-the-future claiming that

``A series of quantum experiments shows that measurements performed

in the future can influence the present.''

(Needless to say, the article presents no real evidence for this startling claim!) Although this quote is from the "teaser" to the Discover article, it is presented in the Wikipedia article in a way which suggests the endorsement of the Wikipedia author.

I thought of rewriting the Wikipedia article, but am hesitant to start what might evolve into a time-consuming controversy, or an "edit war". As a substitute, I am posting on the discussion page of the Wikipedia article a link to the following SampleArticleOnWeakMeasurements.pdf . That is how I would rewrite the Wikipedia "Weak Measurements" article, were I to do it.

A huge problem with the Wikipedia model is that the reader has no way to judge the competence or possible bias of authors. In theory perhaps, questionable articles will eventually be rewritten, but there is no guarantee. For example, the Wikipedia "Weak Measurements" article has been questionable for years. It appears to have been originally written by an anonymous author who claims to have earned a Master of Science degree. The above quote claiming that the future can influence the past was posted by an anonymous editor from an IP address registered to the Procter and Gamble company.

To pass to another topic, I have been reading "Quantum theory cannot be extended" by R. Colbeck and R. Renner, http://www.arXiv.org/arXiv:1005.5173v2 , which considers the possibility of obtaining "standard" quantum theory as a special case of a more general theory. An example would be to obtain quantum mechanics as a special case of classical mechanics via an assumption of classical "hidden variables", a possibility which is ruled out (under certain assumptions) by Bell's theorem. The authors rule out more general possibilities. However, I am not sure that I can agree with all of their assumptions. I would be interested in discussing this article with anyone who has been reading it.

October 30, 2010

While browsing the web, I came across an article from the April, 2010 Discover Magazine, entitled "Back to the Future",
http://discovermagazine.com/2010/apr/01-back-from-the-future , whose "teaser" summary stated:

``A series of quantum experiments shows that measurements performed

in the future can influence the present.''

Quite a claim! Direct experimental evidence for influence traveling backward in time! Despite my dubious impressions of the scientific accuracy of Discover magazine, I couldn't resist clicking on the link to bring up the article.

The first page was mainly a reasonably accurate exposition of standard quantum-mechanical ideas. Then the author, Zeeya Merali, turned on her warp drive and
took off into some kind of intellectual hyperspace. Quotes and opinions were attributed to well-known physicists which will (or should) cause many raised eyebrows. Certainly mine went up.

The article contained a link to another article in the American Physical Society (APS) expository journal Physics 2,32 (2009),
http://physics.aps.org/viewpoint-for/10.1103/PhysRevLett.102.173601 , by S. Popescu, a well-known physicist. I was astonished to find that the general drift of the Popescu article was much the same as that of the Discover article. For example, it states:

"... does time indeed flow in two directions in quantum mechanics? ...
As far as I can tell, Aharonov, Albert, and Vaidman hold the view that one should indeed accept this strange flow of time. I fully agree. Not everybody agrees though, and this is one of the most profound controversies in quantum mechanics.''

Wow! It certainly was news to me that there was any controversy over whether time flows forward, backward, or both directions at once (whatever that might mean!), much less that the issue was regarded as ``profound''!

The thrust of the article was that weak quantum measurements somehow validate Popescu's view that ``one should indeed accept this strange flow [both forwards and backwards] of time''. Since I am very familiar with the mathematics of weak quantum measurements, I eagerly dove into the article to find the evidence for this striking conclusion.

It turned out that the article didn't present any real evidence, and I thought it was highly misleading. If interested in a more technical analysis, click CommentsOnPopescuPaper.pdf . (This is nine pages, so may take a noticeable time to download with a slow connection.) This analysis, originally posted on October 30, 2010, was substantially modified on Nov. 5, 2010. Nothing in the earlier version was incorrect, but the later version is more explicit and considers more plausible guesses at the possible meaning of undefined symbols in the Popescu paper. Further minor edits were made on Nov. 22, and Nov. 28, 2010.

___________________________________________________________________________________________________________________

Originally, this page was intended for reviews of papers which I read carefully.. But that turned out to be such a large and tedious task that I abandoned it after constructing partial reviews of a few papers. Perhaps I shall return to the task at some future time. But right now, I am reading papers far faster than I could hope to review them.

Brief comments on a few I have recently read follow.

Tai-Gon Noh, "Counterfactual Quantum Cryptography'' , Phys. Rev. Letters 103, 230501 (2009)

Presents a scheme for distributing a cryptographic key whose main feature, it is claimed, is that "a particle carrying secret information is not in fact transmittted through the quantum channel". I'm not convinced that the setup descibed will work as the author thinks, but this could be only because I don't understand it properly.

This paper was featured in the 12/21/09 "This Week in Physics" email distribution by the American Physical Society (APS), with headline "The mere possibility of a quantum transmission, rather than its actual occurrence, may enable key distribution in quantum cryptography". I would be interested to hear from anybody who has read this paper carefully and either has doubts or believes it sound and would be willing to answer questions about it.

L. Heaney, A. Cabello, M.F. Santos, and V. Vedral "Extreme non-locality with one photon" , arXiv: 0911.0770v1.

Very interesting "all-or-none" theorem in which a certain result must occur with certainty for local theories, but has vanishing quantum-mechanical probability in a certain limit. Uses bosonic symmetry of photon wave-function, uncommon in Bell-type arguments. I had some trouble reading this, but eventually decided that it seems basically sound, though parts of it are still obscure to me.

Around October, 2009

    My recent paper, ``Quantum weak values are not unique. What do they actually measure?" , was rejected by Foundations of Physics, largely because of partial overlap with an interesting recent paper of R. Jozsa, "Complex values in quantum measurement", Phys. Rev. A 76, 022103 (2007).   I question whether the overlap is sufficient to justify rejection, particularly since the Jozsa paper relies on uncontrolled approximations and therefore is less mathematically rigorous. However, I don't plan to submit it elsewhere. I don't think the mathematics in the paper (mainly finite dimensional linear algebra) is sufficiently interesting for the Journal of Mathematical Physics, and I can't think of another good journal where it might get a careful reading.

    To see the referees' reports along with comments on them, click on refcom.pdf .     The version of the paper on which the referees report is Version 2 .

    Useful comments of one of the referees are incorporated in Version3.pdf .     This version is mathematically almost identical to the original, but some of the exposition has (hopefully!) been improved and the Jozsa reference added, along with an an "Afterword" section.    This will be submitted to the arXiv in early Jan., 2010.

       Problems are not expected, but I have had past problems with arXiv submissions which included referees' reports (even anonymous ones). They claim there might be some issue with copyright violations, but that seems to me farfetched and hypocritical, given that they archive numerous copyrighted papers with typography which makes it likely that they were directly copied from the APS website ("PROLA"). There seems to be a culture of "don't ask, don't tell" regarding copyrighted material in the arXiv. My "Version 3" does not directly quote the referees' reports (paraphrases are OK, or at least were previously), and only refers to them in passing, so I'm not expecting problems.

    It seems unfortunate that the arXiv prohibits referees' reports. In theory, these are supposed to be careful peer review. Why should journals object to authors making them public? (I have never heard of any journal that has objected, which makes the arXiv's sensitivity to the issue even harder to understand.) In my case, I want potential readers to know why the paper was rejected, and in particular that there was no objection to its mathematics.