Category Archives: Career

Scientific madeleines

The two conferences I attended these last weeks (CEQIP and Vaxjo) were pretty good in science, food, drink, location and atmosphere. For me, they were also full of Proustian madeleines: I have met again so many colleagues and realized how they have actually shaped my life, even when the interaction had been short.

  • Mario Ziman is one of the organizers of CEQIP. I met him in my very first conference in quantum information, in the castle of Budmerice near Bratislava, back in 2001. He was doing his PhD under the supervision of Vladimir Buzek, I had recently started my post-doc with Nicolas Gisin. As an outcome of those discussions, Mario and I (and Nicolas and Vlado and another student called Peter) worked in two papers about entanglement and thermalization. At that time, it was a rather unusual topic; now it is a big one, only in CEQIP we had at least three presentations. None of the young authors was probably even aware of our old works, but Mario and I knew better than struggling for recognition: we simply sat there in the back, enjoying the progress of the field and exchanging nods.
  • I have had fewer interactions with the other organizer, Jan Bouda; but I cannot forget a funny moment when he was visiting Singapore, probably in 2007. In the old big office of was to become CQT, Andreas Winter, Nicolas Brunner and I asked him to explain his research. He started out: “I don’t know if you are familiar with quantum cryptography”… This time, I discovered that Jan is very familiar with Moravian wines and their weaker and stronger relatives.
  • Another Slovak in CEQIP: Martin Plesch. He is presently working in Brno and has picked up the topic of randomness. In the conference in Budmerice in 2001, he was an undergrad. He had been tasked to drive Nicolas Gisin and me to Vienna airport on the last day. It was raining, we were a bit late, and Martin was going rather fast on those country roads, keeping really, really close to the car in front.
  • In Vaxjo I met again Hans-Thomas Elze, a German working in Pisa, who is the organizer of a series of conferences in Tuscany. When I went in 2004, it was held in Piombino. At that time, Hans-Thomas was still working in Brazil: as a result, the proceedings of that conference were published in Brazilian Journal of Physics. My paper dealt with an unconventional question and (as you can imagine from the journal) was forgotten until the group of Stefan Wolf made a great progress in 2011. The final solution of the problem appeared in Nature Physics. In Vaxjo, Hans-Thomas invited me to attend his next conference in September 2014. I don’t think there is an Etruscan Journal of Physics, but we’ll see…
  • Since a few years, I coincide with Mauro D’Ariano at least once per year and we always have good conversations. In the middle of complaints about bureaucracy, punctuated by the typical Italian word –zz-, he keeps an exemplary scientific drive. A few years ago, we were having fast food lunch in the March Meeting in Boston. He was telling me that, in his maturity, he wanted to start tackling “really serious” problems. Concretely, he had been reading a lot about field theory, cosmology, relativity… and was declaring his disappointment in finding gaps in the usual arguments. He had decided to try and reconstruct physics from scratch… well, from some quantum form of scratch. Normally, I tend to dismiss beginners who find problems in what others have devoted their lives too — but here, and with Mauro, I could only agree. A few years have passed: his attempt of reconstructing all that we know from basic quantum building blocks has not hit the wall: on the contrary, he and his collaborators are deriving more and more results, and even the “experts” start taking them quite seriously. Thanks Mauro for showing what serious and constant work can do!

Why am I writing all this? For no special reason other than to record minute events and people who are part of my life of a physicist.


The decline of impact factors

The influence of the impact factor is declining, according to a statistical survey which I reached starting from a blog post in Physics Today.

Many, including myself, shall certainly welcome a scientific world in which it won’t be true any longer that “a research published in Nature is, by the very fact, of the highest quality” and that “a young scientist who has published in Nature has far higher chances of getting a job“. But we don’t have to forget that the issue is deeper.

In the past, careers in science were supposedly determined by a panel of wise men (I would like to add “and women”, but it would be an anachronism): as well known, oligarchy is fair only in the eyes of those who share the same wisdom as the oligarchs. Presently, the panel of wise persons is still required for hiring, promotions etc, but there is a request of control by an independent, supposedly neutral authority. This motivates the demand of metrics, may reduce the influence of the whims of some people but introduces other problems. I fear that we won’t hit the perfect system.

Back to the statistical survey: figures 4 and 5 are really intriguing: they indicate that only few of the most cited papers are published in the most cited journals, and the percent is declining since around the year 1990. I am not sure if this is an instance of Simpson paradox… What is even more intriguing is that each figure has two graphs, and it seems to me that, by the definitions used, the two graphs should add up to 100%; but they don’t. So either something is wrong with me, or with this analysis: better finish this post and go back to work.

It will not backfire

Yesterday I was talking with a colleague about some sloppy papers published in the (supposedly) best journals — don’t try to find out which papers: you won’t guess, the sample is too big. At some point, my friend said about the authors: “It will backfire on them”. He said it with a point of sadness, because he has sincere concern for those people. I have thought it myself many times. But… will it really?

How many people are prisoners of their lust and commit horrible crimes! Many, probably most, go unpunished, even by their own conscience that they have managed to silence. Why should anything happen to people who are just prisoners of their mathematics, whose only mistake consists in not noticing that their definitions do not describe reality?

How many people commit financial crimes and injustices that ruin lives, and live without worries other than that of being one day stolen of their riches by poor fellows who will be called “criminals”! Why should some scientists, very decent fellows, be the victims of unfailing divine wrath just because they embellish (I am not speaking of faking) their results in order to get additional 5k$ per year of travel money?

No, I don’t think it will backfire: I don’t think we will see those sloppy works denounced and their authors forced to make amends. When the lobbying that keeps them going comes to an end, they will probably just be forgotten… but so will most of the works that one can consider “serious”: time is quite blind in erasing stuff.

If you want to uphold supposedly high standards, you must find other motives than the mere fear of being criticized one day.

Complacency in science

I have finally read Galbraith’s Short history of financial euphoria, which Alain Aspect suggested to me during a random dinner chat a few months ago. It’s nice: it’s the first time I understand something about finance. And it triggered a concern about academia.

In finance as well as in academia, people often fall into euphoria over something that is, by all rational standards, rather worthless. In my field of research, for instance, the latest craze is the following process:

  1. Write down a new version of some criterion that tests that “something is quantum” (a new Bell inequality, a new test of contextuality, a version of Leggett-Garg…); the simpler — the more trivial — the better, because of point 2.
  2. Find a couple of friends to do an experiment for you. Better if they have been running their setup for ages and have exhausted all the serious science that could possibly be done with it, because they will be more than happy to learn that their old machinery can still be used to perform “fundamental tests”. Moreover, since your test is simple and simple quantum physics has been tested to exhaustion, you have no doubt that the experimental results will uphold your theory.
  3. If you can, present it as “the first step towards [a big goal]”. Never mind that it is rather the last use of a setup that has made its time (I refrained to use “swan’s song”, because the last song of the swan is supposed to be the most beautiful; the last concert of an 80 years old pop star would be more appropriate a metaphor). If you can’t invoke the future, present it as “the conclusive proof of [some quantum claim]”. Never mind that the claim is usually always the same, namely, that results of measurements are not pre-established, that there is intrinsic randomness, or however you want to phrase it. Also never mind the fact that there cannot be a “conclusive claim” every month.

The euphoria mechanism is entertained as follows:

  • The big journals (Nature at the forefront) prefer to publish tons of poor science rather than risking and losing a single real breakthrough. So, if someone claims to have solved “the mystery of the quantum” (the general readership of Nature finds quantum physics mysterious), better take them seriously.
  • In turn, people notice that “if you do that, you publish in Nature”. Since “that” is not that difficult after all, it’s worth while going for it.
  • Once you have published in Nature (or Science or…), you are hailed as a hero by the head of your Department, by the communication office of your university, by the agencies that granted you the funds.
  • Put yourself now at the other end, namely in the place of the one who would like to raise a dissenting voice and reveal the triviality of the result. All the legitimate instances (peer reviewed journals, heads of prestigious Departments, grant agencies, even popular magazines and newspapers!) are against you. Isn’t it “obvious” then that you are only venting your jealousy, the jealousy of the loser?

So far, the analogy with financial euphoria is clear. I guess (though I have not studied the statistics) that the speed of the crash is also analogously fast: it happens when some of the editors of the main journals take a conscious decision of having “no more of that”, because they realize that there is really nothing to gain. The rumor spreads that “refereeing has become tough”; the journals are accused of having become irrational since “if they accepted the previous paper, why they refuse this one” (while it’s one of their few moments of rationality).

And the consequences? The same too, but fortunately without criminal pursuits, despair and suicides. The very big fish get out unscathed: either their science is really serious (that is, they have invested only a small amount of their scientific capital in the euphoric topic); or their power is really big (that is, they have invested only a small amount of their political power in backing the euphoria). The opportunists will try to follow the wind as they should, and will be forgotten as it should. Those who face uncertain destiny are the young fellows, who were doing serious science when the euphoria caught them at the right time and the right place. Because of this, they have been raised to prominence. Somehow, all their capital is invested in that topic. Will they be able to find their way out and continue doing serious science? Or will they end up teaming with their buddies, set up a specialized journal for themselves and publishing there until their old age? If one day you find me as the founder of a journal called “Nonlocality”, please wake me up.

Happy Easter!

Theorists collaborating with experimentalists: a tentative guide

This post is triggered by some of my students. I could give them my own advice directly, but I prefer to write it here because they may benefit from other valuable feedback. The issue at stake is pretty specific: the role of theorists collaborating with experimentalists. The background is my own, limited experience, the classification is as crude as it gets, the analysis proposed here is not the only possible one and is not even always suitable — so, let’s start!

It seems to me that theorist can contribute in four ways to experiments:

  1. Vision: come up with a new concept. It can be very general (say, quantum optics; quantum computing; quantum cryptography) or more specific (say, squeezed states; measurement-based quantum computing; quantum repeaters), but in any case it opens paths that were unexpected before. You won’t find these ideas planned in research proposals: they “happen”. I don’t suggest you base your career on the hope of having such a flash of genius (though you should be ready to recognize it, if it comes).
  2. Tools: develop the necessary theoretical understanding. To continue with the examples above: develop the formalism of quantum optics; invent fault-tolerant architectures; provide the formalism to do security proofs.
  3. Proposals: suggest that a given experimental setup can be used to observe some interesting effect, and do a rough first feasibility study.
  4. Specific description: take a real experiment and describe the physics, to the point where your theory matches the data.

As you can understand, these categories are not tight: for instance, some proposals make it directly into an experiment (nowadays, this is the route of choice to publish your proposal in Nature).

OK, now: here you come and have to decide in which direction to go. You may want absolutely to study a type of experiment: then you need to know what people in that field would appreciate. Or you may want to spend your life (say) inventing proposals: then you need to assess which experimental field is ripe for those. In both cases, the crucial insight for me is: there is a strong correlation between the role of a theorist and the stage of development of the experimental field:

  • At the beginning of a field, proposals are really important; they are also the fast way to celebrity (example: Cirac-Zoller first proposal of a logic gate in quantum computing). If you are up for a longer-term investment, go for tools even at this stage: your effort will be appreciated with a lag, but when the moment comes, you are seen as a pioneer and you are among the few of can really make a difference (example: the work of Norbert Lutkenhaus on unconditional security of quantum cryptography).
  • Once the field is mature, proposals must become really relevant (some physics journals can be seen as a cemetery of irrelevant proposals). Rule of thumb: if no experimentalist cares about your proposals, with overwhelming probability you are not the misunderstood genius, but just the delayed fellow (though, of course, exceptions are possible). At this stage, tools are the most appreciated contribution of theorists: if you develop them, you can choose to keep contact with the labs, or you can take the way of mathematical physics and develop them for their own sake. Both ways are serious; my advice is, but whichever you take, keep an eye on the other.
  • When a field is so mature that even the tools are fully developed, there is little left to do other than specific descriptions (this is the case, for instance, of quantum optics per se, i.e. aside from possible applications in quantum information). Specific descriptions of experiments are tricky. First, you need to check if the experimental group “needs your service”: some groups, for instance, have developed their tools so well, that their experiments are “textbook experiments”, which means that anyone who can follow a textbook can do the theory. Now, if your help is welcome, it is normally very welcome. Since there few people able to do that (compared to the mass of people contributing to the cemetery of proposals), you will be noticed among the experimentalists and may be asked for various collaborations. This is great for a PhD and, if you have such competence, you would do well in keeping it alive for the rest of your career. But you have to do something else as well, if you want to get a position: you need to show that you are also capable of original work (see why in a previous post).

How to convey the wrong message

Last week, two undergraduates I know managed to convey the wrong impression about themselves and their work in a remarkably instructive way. They have learned from their (ultimately harmless) mistakes. Maybe someone else can learn too.

Case 1: a student presents the progress in his project. He starts by stressing that the title has changed because the initial project proved too ambitious. The rest of the talk is a review of some schemes for atom cooling: nice and clear, but covering pretty well known material and leaving important schemes aside. You are listening to him. What do you conclude?

Here is a pretty reasonable analysis: the student did not match the expectations of the supervisor, so the initial ambitious project was tuned down to something hardly more than a review of literature.

Here is the truth: the incompetent fellow, if anyone, is the supervisor (myself), who did not evaluate correctly the difficulty of the initial project. The student is doing very well, he has done much more than a simple review in terms of calculations and simulations. The review was simple because I asked him to use graphs and pictures instead of equations; it was incomplete because the goal is to describe a real ongoing experiment, not to review the whole field of atom cooling!

Where did the student fail? Here are some hints:

  1. Opening the talk by stressing that the focus of the project has changed was the wrong thing to do: it conveys the message that something has gone wrong. Incidentally, the initial topic was pretty similar and nobody would have noticed the change.
  2. The student embarked in the usual idiotic “atom cooling is a fundamental whatever-not in modern physics, interesting both for our understanding of nature and for applications” and failed to mention the REAL motivation, which is the description of an experiment which is really happening two floors below.
  3. The talk was too simple. One must be clear of course, but if it is a research project, one must devote one or two slides to show off — I mean, to convey what has been done.

Case 2: after a few months of research under the direction of a post-doc, a student is asked in the office of the professor (a Singaporean Chinese, which matters for what follows). The professor starts by asking “What have you learned of this field so far?” and the student replies “Nothing much really”.

Here, you don’t have to be a professor to guess the rest. What is more astonishing is the background story.

The truth is that the student had learned a lot and was aware of it. But she feigned ignorance in order to give the professor the chance to explain things from the beginning and learn from his insight! She thought that, by acting this way, she would show how eager to learn she is and how much she appreciates the wisdom of the professor.

This attitude, to this extreme, can only be found in students who have been formed in the Confucian style. But a milder form happens everywhere: for instance, when a professor asks in a lecture “Do you know this or do you need a reminder?”, almost always the students ask for the reminder (maybe there it’s also a trick to slow down the pace and trick the professor into not covering too much new material). In the context of master-to-disciple relationships, it may have its value (though I personally hate it). But if you are going into research, you have to show what you know and admit what you really don’t know: both false humility and false confidence will be detected and signal the end of your application.

A tale of 2011

Many things happened in 2011, of which I can only be thankful. I wanted to consign one to record, which may otherwise be missed, because it is about a “failure” — or better said: a beautiful reaction to a disappointing realization.

Starting in August 2010, a student of mine, Thinh, had been studying a new class of protocols for quantum cryptography, inspired by a previous work. By April, he had managed to define the key mathematical objects to very general scenarios. This was his Final Year Project (FYP), which was awarded as “Outstanding” by the university. A few months later, together with Lana (post-doc), we prepared a paper and submitted to Physical Review Letters (PRL; for the unaware: one of the most prestigious journals for physics).

When the referee report came, the tone was expected: “good work but not of enough broad interest” — very common nowadays for quantum cryptography. The referee stressed how he/she liked very much our generalization, i.e. Thinh’s result. With a few modifications, we could have had the paper published in Physical Review A (PRA; a very good journal still, edited by the same society; a Tier 1 journal in NUS, for the sake of the bureaucrats who care about these classifications).

However, one of the small comments of the referee caught our attention: we realized that the family of protocols we had considered was uninteresting! In a nutshell, these protocols collect a lot of information, but then discard much of it and rely on the rest. Why should one do so?? In other words, all that we did was correct and even elegant, but the object of our study was sort of pointless.

Now you see the alternatives we were facing: (1) skip this awareness under the carpet, do the modifications suggested by the referees and submit to PRA, with quasi-certainty of being accepted; (2) forget about this paper and write rather a technical note, explaining why these protocols are not interesting, to be sent to a very specialized (i.e. less visible) journal. For me, there was no doubt that (2) was the correct course, but I let Thinh and Lana decide — and I am very proud to say that they took the right decision 🙂 The paper has duly been re-written and is under consideration in a specialized journal of our field.

Now comes the scary part of it. I told this story to several friends working in the academic world, over coffees or lunches or other informal meetings. Many of them, especially the younger one, were astonished: “Wow, you guys are so honest! I know many who would never had dropped the chance of publishing in a Tier 1 journal”. For myself, I am sure that Thinh and Lana have made a bigger step in their career by choosing the right course: if you keep your standards high, Tier 1 publications will come.

Happy New Year!


Quantum cryptography and the cycle of life

I never dared spelling it out so bluntly, but I have been thinking for quite some time that “quantum cryptography is dead”. I have been wrong. The dynamics is instructive enough to be recorded here, hopefull it will help others to avoid such mistakes.

Last week, I went to shake some friends’ hands at a conference on quantum cryptography in Zurich and present our latest work in that area. Some predictions I made two years ago have been strictly fulfilled: the field has mainly split into very technical maths and very technological developments. However, in spite of this growing specialization, the experimentalists and the theorists still talk to each other and mutually enrich their topics. Moreover, the corridors of the conference were a hive of new ideas, experimental challenges, new shared interests…

Then I understood.

The topics of quantum cryptography, which we summarized in a review a few years ago, are indeed dying. But if a field is healthy, the “old” topics should be dying: the faster the death rate (within reasonable limits required to reach sufficient depth), the better. The fact that topics die does not mean that a field is dying — the opposite is true: a field is dead when its topics are fossilized.

Trivial, isn’t it? Then, how could I miss it? The answer is simple: my negative stance was the reflection of stupid personal frustrations: a perceived lack of recognition of my work in this field, the impression that the time spent in cryptography had prevented me from developing other topics… That is why the history of Waverley Jong stopping chess resonated so much within me months ago, while I was reading “The Joy Luck club” by Amy Tan.

Thanks God, I had never really quitted. And two days ago, in the train crossing the Alps, I have found a completely new way of attack for one of the big open problems of the field… answer in two years’ time 😉

Steps (4): post-doc

Under the guidance of your Ph.D. supervisor, you have brought a research project to its completion. Now you are a researcher. Next step? Learn to define your research projects yourself! The person who hired you as a post-doc is no longer your “supervisor”: he/she is the head of the research group in which you are integrated. You shall surely learn from him/her, as well as from the other members (after all, we all learn all the time from each other). But what used to be enough during the Ph.D. (namely, to take vague indications, make them concrete and get the results) is no longer enough: you are now supposed to contribute with your own ideas.

… or didn’t you know that the brain energy of your boss, when it is not spent in bureaucracy, is indeed mostly spent in trying to find new ideas? You are going to be appreciated if you help him/her in this task.

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Steps (3): Ph.D.

A Ph.D. is definitely about research. Sure enough, there will be graduate school to improve your general knowledge. Sure enough, your supervisor will provide you with basic training in your discipline and maybe send you to some summer school. Sure enough, you will not be requested to publish a research paper in the first six months, nor in the first year, maybe not even in the first two years. But ultimately you are expected to become a researcher, not just to “learn more”, and even less to “learn from a renowned master”.

This has obvious implications on the choice of the topic and the supervisor. As a student, you liked some fields, you appreciated well-defined problems and very pedagogical teachers that never forgot hbar in their equations. Now:

  • Field. In some fields, almost all that could be done has been done. Most probably, you (and I) know very little about those fields; ideally, it would be good to know more. But you should not ask yourself “what am I going to learn?”; rather, “What are the typical contributions to research in this field? What is the content of the papers that are published these last years?”.
  • Project. In research, a well-defined problem has already been solved. You have to look for a problem waiting to be defined. In other words, your Ph.D. project should sound like “we are going to explore this and that, not exactly knowing what we are going to find, with the hope that this is the right approach to [particular open question]”.
  • Supervisor. Of course, the “Best Teacher Award” does not tell anything about research. But the equations “good researcher = bad teacher” and “good teacher = bad researcher” are equally wrong. If your candidate supervisor is not able to explain you what his/her research is about in simple terms, this is not deep thought, but foggy thought: go and look for someone else!

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