Category Archives: Talks & presentations

Map your project

“I live in a house with garden in North America”. What is preposterous about this sentence? If you speak about your garden, you would not expect the whole of North America as a location. You’d expect something like “I live in a house with garden in the District D, Town T, Canada”.

Well, that is the level of introduction that you get in many papers and scientific presentations: let me make up one. “Quantum computers will have capacities beyond those of any classical computer. Here, we study how a bi-exciton decays in the quantum dots that our group has been trying to fabricate for 10 years with moderate success” (the last half is usually phrased differently, but everyone knows what that means). The point I am making here is: there is a world between the grand dreams of the field and the specific research topic one is dealing with. Following up on a point of a previous post: it is very useful to take some minutes to locate your project on the map of science, with a gradual zoom:

Continent – Nation – Town – Street – House

or, if you prefer:

Grand field – Big challenge within the field – Approach to the challenge – Specific technique [here is “the specifics of my boss”] – My project


Quantum computing – Experimental quantum coherence – Artificial atoms, Quantum dots – Self-assembled GaAs quantum dots – decay of the bi-exciton

Once you have established this map, here is my advice on how to structure a 20 minutes (10 slides) presentation, according to the circumstances. Take it with flexibility of course 🙂

  • Undergrad project: 1-1-3-2-3 [your project is probably an incremental step in your supervisor’s field, so it’s better to take a close focus; but two or three slides on the bigger picture are necessary]
  • PhD Thesis defense: 1-2-2-1-4 [your project is more relevant, so it should contribute at least a bit to the “big challenge”, if not to the grand field]
  • Generic conference: 1-3-3-2-1 [people should remember that “you work in that challenge”, they will forget the details]
  • Conference of your grand field: 0-2-3-3-2
  • Conference of your big challenge: 0-1-2-3-4
  • Specialized workshop: 0-0-1-3-6 [here is where people really care about your technicalities]
  • Grant defense: 5-3-0-0-2 [fine print will be lost, but you have to show that you are doing everyday progress]

A last word: contrary to geography, starting from your project you may zoom out in different ways. For instance, a study on quantum dots may also be seen as belonging to material science, or to quantum optics, rather than to quantum computing… Some people like to bring up all those maps at once: it’s a dangerous option, because it may confuse the audience on your motivation and also give the impression that you are trying to “play up”. The safe option consists in choosing one of the possible maps (the one that your public may like most) and stick to it.


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.

The randomness of evaluation

You may expect that, with all the advices I am giving out, I am a great expert at evaluating presentations… Well, recently I had another proof that the task is probably undecidable.

I was in a panel evaluating student presentations. My guts considered some of them as perfect as one can expect at that level; others as catastrophic as it can get; a couple of them average. But, instead of using guts, we had agreed on an evaluation grid, giving points for criteria like “quality of the slides”, “delivery”, “ability to answer questions”. Then, I had to admit that the delivery of the “perfect” presentations was maybe not so perfect, that the slides of the “catastrophic” ones were not so catastrophic… In short, the analytical approach tends to squeeze the distribution around the average, while the synthetic approach of the guts tends to divide in just “good” and “bad”.

Now, which approach to follow? There is no clear cut answer. In our super-bureaucratized universities, the analytical approach is almost compulsory: the other one would be regarded as too subjective. Moreover… hmmm… I don’t trust myself the guts of some of my colleagues, so why should they trust mine?

However, let me tell you a personal story which shows how the analytical approach can lead to monumental failures. It happened a few years ago.

I was assigned to evaluate some projects for a scientific competition of high school students. In one of the projects, the student had combined several notions and techniques of modern physics, in order to propose a new device. According to all the criteria I was asked to judge, the project was absolutely outstanding: “creativity”, “effort”, “understanding of the basics”, “quality of the report” etc. It suffered from a little problem: the whole proposal did not make any sense! The reason is that those notions and techniques just could not be combined in the same implementation. Unfortunately, “correctness” was NOT one of the criteria we were asked to assess and grade. I had to use the space left blank for “additional remarks” and write there “The whole proposal is flawed”.

This happened twice, evaluating the report first and a poster presentation later. Guess what? Bureaucrats had no time to read the additional remarks, they just summed up the points in the main table: the student won the very first prize with high honors and was invited to attend the international phase of the competition in the U.S.

This is enough to prove my point. However, for completeness, let me tell you how the story ends. Upon receiving notification of the triumph, the school contacted me with an enthusiastic e-mail, amounting at: “We heard that you were involved in the evaluation, now he has to go to the U.S. and we need to make sure that the proposal looks perfect there: would you mind helping us to fix all the remaining details?” To which, I replied in capital letters: THAT PROPOSAL IS FLAWED, followed by the list of flaws. After some days of silence, a much humbler e-mail popped up in my box: “Is there anything we can do to fix it?” Well, to fix the science, one could just replace electrons with neutrons. But since the whole device was meant for use in a computer, the applied part would then become a proposal to put sources of neutrons (= a nuclear reaction) in personal computers, which may not be deemed as practical or even desirable… Finally, the outburst of H1N1 solved the case: all the trips of students to the U.S. were canceled and the project was forgotten. The school and the student retained all the honors — which they both fully deserve, maybe not on the basis of that project, but for the ensemble of their achievements; of course, this is only my guts’ assessment 😉

Presentations: special for students

The mistakes addressed here may happen at any level, but are very frequent in a specific case: students having to present their first research projects within their university. So I’ll write having them in mind; feel free to generalize.

Mistake 1: assume that the basics of your work are known by everyone in the audience

Let me explain this by public confession: in this very moment, I would not be able to recover from my memory such basic stuff as the equation of the incompressible fluid, the critical exponent of magnetization in the Ising model, the definition of the Young coefficient, the reaction to explain which the neutrino was first postulated… Similarly, most of my colleagues may need to be reminded that Bell’s inequalities are tests on two entangled particles, or that quantum cryptography is about Alice trying to establish a secret key with Bob while Eve tries to spy, etc.

We won’t need much to remember these things: show the equations or the schemes on a slide, spend 20-30 seconds of words, and it will come back. So, the matter is not to spend too much time recalling trivialities, just to set rapidly the stage.

Mistake 2: assume that you have show all that you have done (especially the tedious part)

Many students think that they have to impress the audience with their advanced results; or even worse, that they should show how much they have worked. The tedious part of your work must indeed be reported somewhere: in the written report that normally accompanies this kind of university projects. There, there must be lines and lines of code, of equations, of calibration procedures for your devices… But not in the oral presentation.

Why? Well, my explanation is: a reader can choose which parts of your report to read carefully and which to browse fast; but in an oral presentation, the audience cannot really choose. So, since you have only one message to convey, try not to convey your sufferings 😉

Last year we had a fantastic presentation by a student on chaos-induced tunneling (a topic in quantum chaos, of which I knew nothing before). He introduced the main ideas, then showed one (one!) graph and said “this is the spectrum for the model I have studied: this peak corresponds to this orbit, etc”. It was patent to everyone that, in order to get there, he had to write many complicated equations in a computer, then sort out the results — but he was kind enough not to bother us with all the definitions and show us directly the digested result.

As a counter-example, I remember a student who spent her presentation telling us how she wrote a code to map a database that was using x=0 or 1 onto another database that was rather using x=+1 or -1. The audience can safely assume that you have made no mistake in such technicalities. Incidentally, that student had forgotten to tell us what the information in the database was…

Mistake 3: lack of suitable citations

I have seen many presentations in which the only references given looked like: [Very famous fellow 1905], [My supervisor 2007, 2009]; the latter being the two articles, often published in minor journals, that the supervisor suggested as starting point. At the end of your project, you are supposed to know many more references, notably books and review papers.

A correct presentation has:

  1. Basic introduction, with reference: [Very famous fellow 1905]
  2. Overview of progress along the years, with reference: [Book 1960], [Recent review 1998], and maybe a couple of milestone papers
  3. Scope of my project, with reference: [My supervisor 2007, 2009] and [some other active fellow, 2008].

Mistake 4: repeat blindly what you have read

Let me explain this by two examples I witnessed:

  • Presentation on a source of entanglement by Kwiat et al. The student has read in the introduction of the paper the following motivation: “The generation of entangled photons is promising for applications, for instance in super-dense coding”. He just repeated that sentence in his presentation. I asked him what is “super-dense coding”: he had no idea!
  • Presentation on decoherence. The student writes on a slide that “typical decoherence times are 10^{-23} seconds”. I asked him what physical systems he had in mind; answer “hmmm, none specifically, this is very general”. Well, if it would be so general, we would never have observed any quantum phenomenon! That number is probably an estimate for a macroscopic system.

I like to compare this to a sentence from the 1st Letter of St Peter: “Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have” — just apply this to your presentation: be ready to explain why you are saying that!

If this last point is not clear yet, don’t worry: a new round of presentations is coming soon, I’ll surely have new examples to update you 😉

Presentations (2) let’s begin

What do you start your presentation with? I hear a roaring choir of voices shouting: “The outline!”


If people don’t have a clue on what you are going to talk about, the outline will be spoiled. Your first slide should be a sort of abstract: “I am working in this field, there have been lots of advances, we are currently here, and my talk will present how to move to there”.

Let me illustrate it with an example (it’s not a real presentation, just one I rapidly cooked up for this post). Suppose I want to present the research reported in this nice collaboration between my student Yimin and a group in Bilbao. The title is “Ultrafast gates in circuit QED”. The outline would look something like this:

Hmmm… apart from the fact that “introduction” and “conclusion” are sort of obvious… what is coupling to what? what is a qubit? a gate? come on, what are we talking about? The public can’t appreciate this outline, they will forget it even before you switch to the next slide!

However, consider putting this slide BEFORE the outline:

(it would be even better to add a drawing and maybe some references).

Now it starts making more sense — at least, if you are a little bit into quantum optics. We are speaking of some things that behave like atoms; we want to couple them using some field, in a regime that was not explored before. Now go back to the outline: the talk will describe (1) this new regime, (2) how to build the artificial atom, (3) the proposal for the gate that couples two such atoms.

OK, if you completely unfamiliar with this part of physics, you are as much lost as before on the specific topic of our paper… but you have got the idea concerning the presentation, have you not 😉

Presentations (1) basics

Time for student presentations (talks and posters) is approaching in my university, so let me start a few posts on this exercise. Today, the two basic rules. Disclaimer: I was hesitating in writing these because they are very very basic… but I thought about some presentations I heard recently, and not by students… and decided that maybe it is useful after all 🙂 so let’s go.

Basic rule 1: choose your message and get it through

I bet that each time you were disappointed by a presentation, it was by one of the following two reasons: (i) “I did not understand”, or more precisely “I don’t know what I should have taken away”, or (ii) the content itself was disappointing. For (ii), there is no real remedy. But assuming that the presenter is competent and is dealing with potentially interesting content, the success of the presentation depends on the choice of the message to be conveyed and a correct gauging of the audience.

At the moment of preparing, think: what do I want those people to remember? Normally, one message is enough. Surely you have done a lot of calculations, or have set up a complicated experiment. You can use one slide, or one corner of your poster, to remind all this; but nothing more… unless of course the message you chose to convey is precisely “I toiled a lot for this and now I want you to share in my toil”.

If you don’t choose the message, the message will be chosen for you; and most of the time, it will be “this presentation was a waste of time”.

Basic rule 2: stick to the time

Even if you are the smartest presenter with the most exciting subject, people get very nervous if your talk lasts longer than usual; or if you are so talkative in front of your poster that people don’t manage to get away.

For talks, just run through the presentation once or twice before, fully and aloud. If some friends are ready to listen, great; otherwise, close yourself in your room and do it. Golden rule: 1 slide = 2-3 minutes (yes: a 15 minutes presentation is only 6-7 slides, plus the title!).

For posters, look at the people you are talking to in the eyes: incipient boredom is written there very clearly.