Research lines that lead nowhere (II) to publishing in Nature: unnecessary experiments

Hi rats,

When I was a young muroid, my collaborators and I proved that, for the state estimation of pairs of coherent states of the form \ket{\alpha}\ket{\alpha*}, entangling measurements are more efficient than LOCC measurements, contrary to the case \ket{\alpha}\ket{\alpha}. The result was curious, and I was convinced that we would manage to publish it in a nice journal (at that time, PRA was a nice journal).

Then, something happened. My supervisor told me that he had contacted an experimental group which was willing to prepare pairs of coherent states and perform the optimal LOCC and entangling measurements.

I couldn’t believe my ears. An experimentalist, the superior species, wanted to test our result!! I was joyous and jubilant, because I was not fully convinced by our rigorous mathematical proof. My supervisor and I were so happy indeed, that we held hands and sang and danced together. Then Christopher Robin and Doraemon came with an apple pie, and we all had a nice meal under the shade of the Magic Oak Tree, in Sugarcandyland (Bromley South).

In the real world, however, I was confused and angry. We already knew what was going to happen. What did those experimentalists expect? That quantum mechanics was going to break in an experiment involving two coherent states, a beam splitter and homodyne measurements? That once the setup was complete, the skies would open and a deep voice would say: “thou shall not finish that experiment!”?

Well, the experiment was completed, and, behold, they measured what the theory predicted. Once more, quantum mechanics (and the world!) was saved.

This post is about futile experiments like mine which are perhaps a bit too subtle for an Ig-Nobel prize. You know what experiments I’m talking about: the kind which make you scream “for the glory of Cavendish!!” when you see them featured in the cover of renowned scientific journals. The kind which the theorists involved describe as: “…and then we performed the experiment. I’m sorry”.

Well, I’ve had enough. I won’t stay silent while promising QI theorists and experimentalists waste their talents in meaningless collaborations. Did you know that people in other fields (e.g.: organic chemistry) conduct experiments to actually advance the theory? It’s time to kick some asses.

Before starting my monthly rant, though, let me clarify what this post is not about.

In this post I’m going to discuss six experiments. I won’t criticize the theoretical results underlying these experiments (well, just one), or the technical ability and innovation of the experimentalists who carried them out. What I will argue here is rather the need to perform such experiments. So if I have happened to single out one of your papers and at any time you feel that I’m undermining your work, please come back to this paragraph and re-read it as many times as necessary.

And then be honest: do we really need more experiments like…?

1) Experimental demonstration of 2, 3, 5, 6, 8-photon entanglement.

Contrary to popular claims, we don’t have a use for generic entanglement, so most of these results have no practical application (what is the usefulness of an 8-party GHZ state!?). One could argue that entangling a vast number of particles may be theoretically impossible due to collapse theories, etc., and that it is interesting to see how far we can go. Even so, photons are a very bad candidate to look for violations of quantum mechanics; massive particles seem to me a better choice.

Where does this obsession to entangle photons come from? How many photons will have to get entangled before the topic dies out? For Christ’s sake, somebody write a paper showing how to entangle n+1 photons from n entangled photons, and stop this madness for good!

2) Experimental estimation of the dimension of classical and quantum systems.

The story begins an interesting theoretical study of the correlations generated by classical and quantum systems of dimension d in prepare-and-measure scenarios, followed by a complicated optics experiment where the authors certify dimension four. Unfortunately, certifying dimension four is not that difficult: I can do it with my balls an abacus, or a mango and a watermelon. And there's more! I can remember 9-digit phone numbers, so I can certify dimension 10^9. Don’t study quantum optics, study me!!*

*This sentence won the prestigious award Worst Pick-Up Line Ever 2004.

3) Environment-induced Sudden Death of Entanglement

This project was born dead. The authors present an experimental demonstration of entanglement sudden death for a two-qubit state subject to amplitude decay and phase damping channels. In case you’re not familiar with ESD, here’s the theory of the paper in three pictures:

The ellipsoid represents the set of separable states; the extremes of the stick, the initial and the final quantum state after repeated iteration of the quantum channel. (a) If the channel converges to a point in the boundary of the set of separable states, for certain initial states, the system will enter the ellipsoid in finite time (ESD). (b) For some others, it won't. (c) However, if the map converges to a point in the interior of the set, you will always observe ESD.

Fascinating. Let us now discuss the need for an experiment. The authors claim that “photons are a useful experimental tool for demonstrating [ESD] and, more generally, for investigating quantum channels like [the amplitude decay channel], as the decoherence mechanisms can be implemented in a controlled manner”.

Of course, this is all bullshit, because these two channels are defined mathematically, so one can perform a simple analytical study of the properties of the states which undergo such transformations (which the authors actually do). Implementing these channels in an optical scenario is not going to add any insight, just experimental errors. And as for ESD verification, an in-depth pub study of the different ways to touch an olive with a toothpick is equally revealing and much tastier.

4) Violation of Bell’s inequality in Josephson phase qubits

The CHSH inequality (there are so many Bell inequalities, why does everyone choose the same?) has been violated with photons, ions and cold atoms. So what? Violating CHSH with two yoghourt cans tied with a string is hardly surprising if you allow for locality or detection loopholes. The actual challenge is to violate local realism, i.e., to implement a loophole-free Bell test. If you’re an experimentalist with a genuine interest in nonlocality, don’t waste your time and ours with more non-conclusive games and go for the real thing once and for all.

And don’t make me speak of contextuality experiments; there the “loophole” turns into Madonna’s vagina.

5) Closed time curves via post-selection: theory and experimental demonstration

Synopsis: the authors come up with a model for quantum time machines, mathematically equivalent to teleportation with post-selection. Then, they decide to make an experiment to “test the predictions of the theory”.

OH-MY-GOD! A time travel experiment!! Our heroes travel back to 1955 in a modified DeLorean and accidentally seduce their own mothers in a thought-provoking adventure of self-discovery*.

*More concretely, the discovery that you’re inclined to practise incest.

Well… no. Rather, they perform a very expensive and time-consuming experiment of quantum teleportation with post-selection. Then they verify that, indeed, quantum teleportation gives the same predictions as their time-machine model, which by definition gives the same predictions as quantum teleportation. The paradox is therefore solved in a self-consistent way, Martin McFly’s right hand reappears and he can finally wank return to 1985.

I strongly recommend the authors to travel back in time and remove the experimental part from their letter. Not for me, or for you, but for the students. Think of them and their bleeding eyes when they read your paper!

6) An experimental test for non-local realism

Here an experiment to violate Leggett’s model of crypto-nonlocality is carried out. This experiment, as well as any other one trying to disprove Leggett’s model, is pointless: if a set of bipartite correlations p(a,b|x,y) is compatible with Leggett’s axioms, then it must correspond to the statistics generated by a two-qubit separable state (see arxiv:1303.5124). This implies that any experiment showing entanglement between two photons is a refutation of Leggett’s model. Since two-photon entanglement has been verified ad nauseam, Gröblacher et al.’s experiment was not necessary. This is a case where the theory was simply not advanced enough to embark on an experiment.

Enough blood for today. You have already seen several examples of unjustifiable waste of tax-payer’s money in pointless experiments. Yet many authors of these papers are respectable figures in QI. What is happening?

When the scientific community acts bizarrely, dig in and you will find an important journal at the bottom of the trash-bin.

Some years ago, an unhealthy paradigm of research in QI was established via journal feedback: the duty of theorists is to develop results which are experimentally testable with current technology, while experimentalists are expected to come up with ways to implement the protocols which the theorists devise.

Play by the rules of the game, and you will get rewarded: if you’re a theorist, you will get published in prestigious journals, like Nature or Science, where theoretical Physics hardly ever appears (and if it appears, it is usually in embarrassing forms). If you’re an experimentalist, you can claim that your technical achievements are actually interesting -read “practical”- for quantum information processing.

The negative side, of course, is that many theorists are limiting their theoretical research to subjects where “experimental investigations” can be carried out straightforwardly. Most worryingly, the paradigm has driven experimentalists to theorist hunting, a recent mass phenomenon that I invite you to contemplate at your next theoretical seminar: hordes of experimentalists, sitting on the back row, breathing anxiously, their claws ready to trap any theoretician who can tell them what the hell to do with their current optical setup. It is precisely this obsession to implement experimentally whatever is fashionable in theoretical circles what leads to surrealistic situations where four different groups report experimental boson sampling in the same week.

These are my final messages:

1) Experimentalists: for many of you, the real motivation is the experimental control of quantum systems. Such is a noble enterprise; be proud of your work and stop forcing QI applications into your papers.

2) Theorists: not every theoretical discovery must be complemented with an experiment. E.g.: it is possible to control where soldier crabs walk by projecting them predator shadows; hence, in theory, one can build a computer using swarms of crabs rather than electric currents. However, no serious researcher would attempt to perpetrate such a stupi-. Oh, no.

Yours truly,

The Rat

Judging scientific excellence by the shape of the head

The Rat, 2013.

Hi rats,

At this point, you may be wondering: what the hell...!!!?? 

I can explain everything: being a parasitic animal, I recently joined the ranks of fellowship applicants, and I want to share my experience.

In case the comic is too subtle, I’ll say it in plain English: the final decision about your grant or fellowship is going to be made by non-experts, i.e., individuals who are actually not qualified to evaluate your scientific skills. The success of your application will depend on trifles such as whether you roman-numbered or not your project goals in the Background section of your proposal (veridical). So rather than trying to impress the referees with a creative and coherent research project, you may better put on a white lab coat and type furiously over an illuminated coloured computer keyboard that sounds “teetooteetootee” while a flask containing a green liquid bubbles in the background. You’re doing serious stuff here!

First, about your CV: have you ever been asked to list your ten best publications? Well, don’t make the common mistake of citing your ten favourite papers, because nobody is going to read them anyway; the non-expert referees will go straight for the journal and the number of citations.

Wait! Does that mean that any candidate with a Nature paper on entanglement sudden death will have preference over me!?

Yes, he will.

Incidentally, this reminds me that in the last two months different people have argued that this blog is detrimental for QI, because our community is, oh, so peaceful. By speaking my mind about certain topics, I’m creating a climate of belligerence and unhealthy competitivity that blah, blah, blah.

The thing is, I agree with these people! QI is a paradise... if you hold a permanent position. Because if you don’t, you have to compete for it against candidates with a paper on quantum discord with five hundred citations. So let’s call rubbish “rubbish”.

Coming back to your CV, funding agencies will typically require you to evidence your “capacity to build collaborations”. I don’t understand how this can be relevant, because some of the most dreadful calamities in History started as collaborations between talented individuals, like Glauber and Oppenheimer, or Jackie Chan and Chris Tucker. Fortunately, the non-expert referees can’t understand /don’t care about the quality of such collaborations. So anything fits in this section, like the time I sustained ****** *******berger’s head while he was vomiting in the toilet because he had drunk himself out after being rejected by all the girls in the quantum information workshop. What? Yes, the three of them.

Then, there comes the project. The requirements are clear and contradictory: on one hand, your project must be novel and imaginative. On the other hand, it has to be an extension of your previous results. 

This last demand shows how much science has changed since Richard Hamming gave his inspiring talk You and your research, where he advises researchers to change fields every seven years. Nowadays, you're supposed to work pretty much on the same topic since your graduation day till your retirement. Do you want to change fields? Become a gardener!

As you can see, applying for a scientific grant is infuriating enough to turn Mohandas Ghandi into the incredible Hulk. But the worst is yet to come: read the next paragraph and roar.

In the eve of every referee report deadline, the ghost of Research Results Yet to Come haunts the non-expert referees. Hence they will demand you to detail exactly how you intend to reach your project goals. Now, this may make sense in experimental particle physics, where collaborations involve thousands of people and improvisation is not an option. In theoretical matters, it is patently absurd.

But, absurd or not, proposals like: “I want to prove A, so I will try to prove B, C and D and then connect the results” will be rejected.

“But you are not explaining how to prove B, C and D! How are you going to achieve this?”

“I don’t know! That’s why I need a four-year funding, damn it! To do research and find out!”

Well, that’s not the right attitude. You have to convince the referees that there isn’t the slightest chance that the project is unsuccessful. Two plausible scenarios come to the mind:

a) the project is already finished, and you’re just listing results that you will “come up with” during the next four years;

b) the project is crap.

If we were living in a rational world, in either case the project would not be funded and the candidate would be sent to forced labour in Siberia. Unfortunately, we live in Bureaucracyland, where opinions must be objective, and the only way to get funding for a project is to finish it before the application deadline.

Finally, there comes the part of “national interests”. This is where you argue that what you’re doing is essential for the survival of the human species. Of course it isn’t, but anyone else is claiming so: if you want to stand a chance, I suggest you to claim it too. I pity those poor researchers who waste their time investigating banalities like cancer or global warming! For the same price, they could be working in something really important, like topological quantum error correction... or at least that is the impression that I get when I read certain grant applications on topological quantum error correction.

In this section, I would suggest the funding agencies to demand responsibility: “you said that your research would improve the French economy! Two years later, and government bonds are cheaper than ever! To the guillotine!”.

CONCLUSION

My previous posts have been criticized for being non-constructive (ironically, because that is also a non-constructive criticism). Nevertheless, today I want to finish with a positive note, because I believe that there is a fairer method to decide grants.

It is quite simple: if a grant is to be evaluated by, say, four referees, two experts and two non-experts, the latter should not have access to the candidate’s name, the CV or the detailed project proposal.

They should not have access to the candidate’s CV, because they are not qualified to emit judgement about his/her research capacity in an area which is alien to them. And idem with the project. If you let them have this information, eventually they will come up with a collection of arbitrary criteria to assess the proposal, like, e.g., the number of prizes awarded during the completion of the PhD studies. Those prizes do not exist in many countries; using such a criterion to evaluate international candidates is xenophobic at the very least. Likewise, any other “trick” they may distil from their long experience rejecting promising grant applications could be inadvertently racist or sexist. If you are a non-expert referee and intend to decide the outcome of a fellowship on similar grounds, let me ask you to consider tossing a coin, asking a spirit board or reading the entrails of a sacrificed chicken. At least that way you won’t be introducing systematic errors every time you’re asked to evaluate a bloody grant proposal!

And yet, there is a legitimate role for non-experts in the refereeing process.

Sometimes, certain research communities lose contact with reality and engage themselves in senseless (and endless) scientific production. It is then in the hands of a field outsider to set things right: the job of a non-expert should be to decide if the proposed project’s goals would suppose a benefit for society.

The task is easy: if the candidate states in his project description that “the aim of this project is to create an army of giant singing oysters to conquer Honolulu”, don’t fund him. If, on the contrary, the project description reads: “we will develop a flying voodoo doll that can communicate with pineapples”, accept the damn application and let the experts decide whether it is feasible or not!

Yours truly,

The Rat