The quantum puppies post below was written in response to some excitement generated by recent work from Paul Kwiat’s group at UIUC; specifically, this paper in Nature (which is sadly only available to subscribers). Paul was nice enough to write a little clarification about what they actually did, which we’re reproducing here as a guest post.

Hi,

I’m not normally a Blogger (I also don’t have a cell phone, if you can believe that).
However, given the plethora of commentary on our article (and on articles *about* our article), I thought a few words might be useful. I’ll try to keep it short [and fail ]

1. There has been quite a bit of confusion over what we’ve actually done (due in large part to reporters that won’t let us read their copy before it goes to print), not to mention *how* we did it. For the record—
   1. we experimentally implemented a proposal made several years ago, showing how one could sometimes get information about the answer to a quantum computation without the computer running. Specifically, we set up an optical implementation of Grover’s search algorithm, and showed how, ~25% of the time, we could *exclude* one of the answers.

      Some further remarks:

      - our implementation of the article is not “scalable”, which means that although we could pretty easily search a database with 5 or 6 elements, one with 100 elements would be unmanageable.

      - however, the techniques we discuss could equally well be applied to approaches that *are* scalable.

   2. By using the Q. Zeno effect, you can push the success probability to 100%, i.e., you can exclude one of the elements as the answer. However, if the element you are trying to exclude actually *is* the answer, then the computer *does* run.

      -The Q. Zeno effect itself is quite interesting. If you want to know more about it, you can check out this tutorial.

   3. Unless you get really lucky, and the actual answer is the last one (i.e., you’ve excluded all the others without the computer running, and so you know the right answer is the last element, without the computer running), the technique in 2. doesn’t really help too much, since if you happen to check if the answer wasn’t a particular database element, and it really was, then the computer does run.
   4. By putting the Zeno effect inside of another Zeno effect, you can work it so that even if you are looking to exclude a particular database element, and the answer *is* that element, then the computer doesn’t run (but you still get the answer). Therefore, you can now check each of the elements one by one, to find the answer without the computer running. This was the first main theoretical point of the paper. Contrary to some popular press descriptions, we did not implement this experimentally (nor do we intend to, as it’s likely to be inconveniently difficult).
   5. If you had to use the method of 4. to check each database element one-by-one, then you’d lose the entire speedup advantage of a quantum computer. Therefore, we also proposed a scheme whereby the right answer can be determined “bit-by-bit” (i.e., what’s the value of the first bit, what’s the value of the second bit, etc.). This is obviously much faster, and recovers the quantum speedup advantage.
   6. Finally, we proposed a slightly modified scheme that also seems to have some resilience to errors.

      Taken in its present form, the methods are too cumbersome to be much good for quantum error correction. However, it is our hope this article will stimulate some very bright theorists to see if some of the underlying concepts can be used to improve current ideas about quantum error correction.

2. There have been a number of questions criticisms, either about the article, or the articles about the article. Here are my thoughts on that:
   1. I guess I should disagree that our article is poorly written (no big surprise there ), though I agree 10000% that it is not at all easy to read. There are (at least) two reasons for this:

      - there is a tight length constraint for Nature, and so many more detailed explanations had to be severely shortened, put in the supplementary information, or left out entirely. Even so, the paper took over a year just to write, so that at least it was accurate, and contained all the essential information. For example, we were not allowed to include any kind of detailed explanation of how Grover’s algorithm works. [If you want more info on this, feel free to check out: P. G. Kwiat, J. R. Mitchell, P. D. D. Schwindt, and A. G. White, "Grover's search algorithm: An optical approach", J. Mod. Opt. 47, 257 (2000)., which is available here.

      - the concepts themselves are, in my opinion, not easy to explain. The basic scheme that we experimentally implemented is easy enough. And even the Zeno effect is not so bad (see that above tutorial). But once it becomes "chained", the description just gets hard. (I am pointing this out, because I would reserve the criticism "poorly written" for something which *could* be easily [and correctly!] explained, but wasn’t.)

   2. I agree that some of the popular press descriptions left something to be desired, and often used very misleading wording (e.g., quantum computer answers question before it’s asked - nonsense!). Having said this, I do have rather great empathy for the writers - the phenomenon is not trivial for people in the field to understand; how should the writers (who *aren’t* in the field) explain it to readers who also aren’t in the field. Overall, the coverage was not too far off the mark.

      -To my mind, the most accurate description was in an article in Friday’s Chicago Tribune (the author kindly let us review his text for accuracy before going to print).

Okay, thanks for your attention if you made it this far.

I hope that these words (and the above web link) will clarify some of the issues in the paper.

Best wishes,
Paul Kwiat

PS Please feel free to post this response (in it’s entirely though) on any other relevant Blogs. Thanks.

This afternoon I am embarking on a great adventure - my own walkabout if you like. I am going to India! It takes 2 days to get there and I will be there for 22 days. The reason for the trip is the 2006 International Linear Collider Workshop (LCWS06), being held in Bangalore. I will be visiting a collaborator at the Tata Institute beforehand, and will tour a bit afterwards. In particular, I will be at the Taj Mahal for two major events: a lunar eclipse and my birthday!

Even though I’ve been to India once before, the preparations for this trip have been massive. I’ve switched from film to digital photography and had to invest in all the appropriate equipment and learn how to use it! I am now the proud owner of a Nikon D200 (10.2 Mpixels!) with VRII 18-200mm lens, 4 Gb of high speed flash cards, not one but two spare batteries, and a Wolverine hard disk. If everything works okay, I should be set! In addition, my suitcase is chock full of FOOD (ranging from trail mix, to peanut butter, to granola bars), a bottle of wine (who could go 3 whole weeks without wine??) and enough hand sanitizer to make an entire army germ free.

LCWS05 was held at Stanford last March and I was the workshop organizor. This year I am most happy to just be a participant and enjoy my stay. Internet access may or may not be difficult and I may not be able to blog for awhile.

Gosh, the taxi is here - Bon Voyage!

Maybe in Hollywood, but not necessarily elsewhere….

I should have learned this in high school - then, the local newspaper did a feature each week highlighting a group of seniors from the various schools. There was a theme each week and the group answered questions on topic. I was chosen and was pretty excited about it - until the interview started and I learned the theme was religion. Being my honest, naive, 17-yr-old self, I stated that I was rather unsure about the existence of God and that I thought churches were money making organizations. Naturally, I was quoted in print. In a smaller midwestern town. I received a barrage of truly hateful mail - some letters acusing me of devil worship, others wanting to save my soul. My senior science teacher summed it up best by saying `What you said was probably correct, but it’s not what you say to a newspaper reporter.’ That’s when I should have learned to be careful with reporters.

Two weeks ago, it happened again. The good folks in the SLAC publicity office are starting a feature where every few weeks a piece of work from the SLAC theory group will be highlighted. Great idea, I thought! I was the first guinea pig and was asked to do an interview for an article on a paper I wrote last Spring. The work was cute, has a catchy title, and is published in Physical Review Letters, but is not going to change life on earth as we know it. The article was to be for the internal SLAC newsletter TIP (The Interaction Point) and would also make a brief appearance on SLAC Today, the daily newsboard for the SLAC community. So, co-author Tom Rizzo and I spent an hour with the reporter, we saw a draft of the article and sent in revisions, and they took a few pictures of us at the blackboard. We could not get too technical, we were told, because the article was intended for the general, non-scientific, SLAC community.

Next thing I knew, the headline

SLAC Physicists Develop Test for String Theory

was emblazened on the main SLAC homepage! Then Peter Woit of Not Even Wrong lashed onto it. Then it was picked up by PhysOrg.com, which was subsequently featured by Slashdot. All with a smiling picture of yours truly, supposedly devising a definitive test for all of string theory. AARGH!!!!

The entire article was misrepresented, blown up out of proportion, and I could not have been more upset. Nothing against the good folks at the communications office at SLAC - we worked on this together and none of us saw this coming. Nonetheless, I did not have a good week.

The remedy? We posted comments on all the blogs and revised the article to include the scientific details which then put our work into proper context.

So, what’s all the fuss about? There has been heated discussion, on this blog and elsewhere, regarding the fact that there are no known scientific tests to prove or disprove the existence of string theory. We came up with an idea that could test classes of string theories, within a very particular framework, which may or may not be present in nature. If this framework exists, then we can test for whether there are 10 or 11 dimensions of spacetime, as Sean recently explained is favored by critical string theory, or not.

Here is the revised version of the article:

SLAC Physicists Develop Framework-Dependent Test For Critical String Theory

String theory solves many of the questions wracking the minds of physicists, but it has one major flaw — there are currently no known methods to test it. SLAC scientists have found a way to test a particular version of this revolutionary theory. The test applies to a class of critical string theories which posit that there are 10 or 11 dimensions in our universe — no more, no less.

This past December, Joanne Hewett, Thomas Rizzo and student Ben Lillie published an article in Physical Review Letters which shows theoretically how to measure the number of dimensions that comprise the universe. By determining how many dimensions exist, Hewett, Lillie and Rizzo hope to either confirm or repudiate critical string theory under specific conditions.

The first three dimensions, length, height and width, are familiar to all of us. The fourth dimension is time. But what are the extra dimensions? “Imagine a tightrope stretched between skyscrapers,” says Hewett. “If you are watching an acrobat walk across it — the tightrope looks like a line. But if you are watching an ant walk on the tightrope, you can see that the tightrope is thick and round.” The extra dimensions postulated in string theory are like the tightrope with an ant on it; they are too small to see unless you get really, really close.

Hewett, Lillie and Rizzo found that if so called micro-black holes, which are smaller than the nucleus of an atom, exist, they can be used to determine the number of extra dimensions. If scientists were to smash two high energy protons together they could theoretically make such a micro-black hole. Such a collision could happen at CERN’s Large Hadron Collider (LHC), which will become operational next year. Once created, the micro-black hole decays quickly and emits over a dozen different kinds of particles such as electrons, neutrinos and photons, which are easy to detect. Using the predicted decay properties of the black hole into neutrinos, Hewett, Lillie and Rizzo solved complex equations to determine if our universe has 10, 11, or more dimensions — perhaps too many dimensions to be explained by critical string theory.

More technically, the analysis applies to models of extra dimensions where micro-black holes can be formed with a size smaller than the curvature of the additional dimensions and where the fundamental particles which make up our universe do not reside in the extra dimensions. These micro-black holes must also exist at an energy scale which can be probed at the LHC. Under those very specific conditions, the test holds. These conditions are possible within string theory, but need not be present.

“The computations were so massive, we had to make extreme use of the Babar UNIX farm,” said Rizzo.

Of course, string theory hasn’t been tested yet — experimental evidence is necessary. Additionally, Hewett, Lillie and Rizzo’s analysis can only disprove critical string theory; it cannot prove it.

“If they see black holes at the LHC, they’ll definitely do this analysis,” says Hewett. “This would tell us about the fundamental nature of the universe.”

Quantum mechanics, as we all know, is weird. It’s weird enough in its own right, but when some determined experimenters do tricks that really bring out the weirdness in all its glory, and the results are conveyed to us by well-intentioned but occasionally murky vulgarizations in the popular press, it can seem even weirder than usual.

Last week was a classic example: the computer that could figure out the answer without actually doing a calculation! (See Uncertain Principles, Crooked Timber, 3 Quarks Daily.) The articles refer to an experiment performed by Onur Hosten and collaborators in Paul Kwiat’s group at Urbana-Champaign, involving an ingenious series of quantum-mechanical miracles. On the surface, these results seem nearly impossible to make sense of. (Indeed, Brad DeLong has nearly given up hope.) How can you get an answer without doing a calculation? Half of the problem is that imprecise language makes the experiment seem even more fantastical than it really is — the other half is that it really is quite astonishing.

Let me make a stab at explaining, perhaps not the entire exercise in quantum computation, but at least the most surprising part of the whole story — how you can detect something without actually looking at it. The substance of everything that I will say is simply a translation of the nice explanation of quantum interrogation at Kwiat’s page, with the exception that I will forgo the typically violent metaphors of blowing up bombs and killing cats in favor of a discussion of cute little puppies.

So here is our problem: a large box lies before us, and we would like to know whether there is a sleeping puppy inside. Except that, sensitive souls that we are, it’s really important that we don’t wake up the puppy. Furthermore, due to circumstances too complicated to get into right now, we only have one technique at our disposal: the ability to pass an item of food into a small flap in the box. If the food is something uninteresting to puppies, like a salad, we will get no reaction — the puppy will just keep slumbering peacefully, oblivious to the food. But if the food is something delicious (from the canine point of view), like a nice juicy steak, the aromas will awaken the puppy, which will begin to bark like mad.

It would seem that we are stuck. If we stick a salad into the box, we don’t learn anything, as from the outside we can’t tell the difference between a sleeping puppy and no puppy at all. If we stick a steak into the box, we will definitely learn whether there is a puppy in there, but only because it will wake up and start barking if it’s there, and that would break our over-sensitive hearts. Puppies need their sleep, after all.

Fortunately, we are not only very considerate, we are also excellent experimental physicists with a keen grasp of quantum mechanics. Quantum mechanics, according to the conventional interpretations that are good enough for our purposes here, says three crucial and amazing things.

• First, objects can exist in “superpositions” of the characteristics we can measure about them. For example, if we have an item of food, according to old-fashioned classical mechanics it could perhaps be “salad” or “steak.” But according to quantum mechanics, the true state of the food could be a combination, known as a wavefunction, which takes the form (food) = a(salad) + b(steak), where a and b are some numerical coefficients. That is not to say (as you might get the impression) that we are not sure whether the food is salad or steak; rather, it really is a simultaneous superposition of both possibilities.
• The second amazing thing is that we can never observe the food to be in such a superposition; whenever we (or sleeping puppies) observe the food, we always find that it appears to be either salad or steak. (Eigenstates of the food operator, for you experts.) The numerical coefficients a and b tell us the probability of measuring either alternative; the chance we will observe salad is a², while the chance we will observe steak is b². (Obviously, then, we must have a² + b² = 1, since the total probability must add up to one [at least, in a world in which the only kinds of food are salad and steak, which we are assuming for simplicity].)
• Third and finally, the act of observing the food changes its state once and for all, to be purely whatever we have observed it to be. If we look and it’s salad, the state of the food item is henceforth (food) = (salad), while if we saw that it was steak we would have (food) = (steak). That’s the “collapse of the wavefunction.”

You can read all that again, it’s okay. It contains everything important you need to know about quantum mechanics; the rest is just some equations to make it look like science.

Now let’s put it to work to find some puppies without waking them up. Continue reading ‘Quantum interrogation’

It is worth taking the time out to listen to one of the reports from this morning’s “Weekend Edition Sunday” on NPR. The page summarizing the report is here. There are two interviews of some length and depth. (They are longer than the extracts you may have heard on the radio, so have a listen again, if interested.)

One is from Dr. Donald Kennedy, the editor-in-chief of ‘Science Magazine’. He does a good job of summarizing the discussions that have been taking place about the Bush administration’s attitude to science and scientists (over a wide range of issues: climate change, energy policy, the Environmental Protection Agency, etc… many of these have been discussed on this blog), he applauds some of the recent funding announcements from the administration on science investment and education, but has a lot more to say about the big picture of science and science policy in this country. See also a recent editorial he wrote at this link.

The other interview is with Dr. John Marburger, the administration’s science advisor. He spends a lot of the first part of the interview discussing his vision of what the new “competitiveness initiatives” are all about. He also talks a lot about the education initiatives…. I was particularly interested to hear about their efforts to encourage real scientists and engineers to come into the high school classroom and talk about what they do…give students a chance to meet and talk to real scientists. This is good…..You know how important I think this is from all the blogging about that I do on it. I hope that many of us take advantage of any support that is to be given to make this sort of thign happen more. Look out for it please!

His main response to the issues that Kennedy raised is remarkable. He basically said that the criticisms by the scientists are irrelevant. He has other things to say, which you should listen to as well, but his message there sounds to me to be rather confused….how can you dismiss what the scientists say and still claim that there is a dialogue? The interviewer notes this, but Marburger simply steers away from the sore spots and pretty much says that everything is fine and dandy, it’s all under control, the administration (e.g. on climate change) have “strategies” and they are getting on with. Sigh.

Well, have a listen. The interviews themselves, but also the contrasts between them, are illuminating. Kennedy seems to think that this administration is particularly bad with regards science policy, and as a result the scientists are more vocal, and the arguments are lot more heated than before, while Marburger says that it is not the administration tha is responsible for the increased tensions in these debates, but the fact that there are more places where science is relevant to societies problems. He says -and here I totally agree (see my many posts on this)- that this is why everybody needs to become more educated in basic science.

Whatever the reasons for the extra tension in the science-meets-politics arena -it is probably a little bit of both- I really think that we should not be looking forward to going back to a time when science was less on the political agenda than it is now. Hopefully it is here to stay, and it is the quality of the debates (and the education that everyone has about the debates) that should be improved as we move forward.

-cvj

Saturday night, and I’m doing a bit of blogging after clearing weeds in the garden. Shouldn’t I be getting ready to go out on the town and live it up a bit? Perhaps. I’ll see how I feel in an hour or so. Let me tell you a bit more about my Taiwan wanderings. I’m cheating a bit by borrowing (heavily edited and abridged!) extracts from one of the other blogs I keep…this one being a real diary that lives on my laptop, which I started while on Walkabout as a means of clearing my head (the point of the trip): essentially talking to myself (I recommend it).

At some point in my stay in Hsinchu on my Walkabout, I began to look for places that served good coffee, where I could sit and do a bit of thinking and some work, (sometimes both!). Both coffee and atmosphere are two important fuels for this type of work, at least for me. (This was before moving to Taipei and finding the various excellent tea and coffee places near National Taiwan University that I began to haunt regularly. I think I mentioned those in earlier posts about the trip. See e.g. here and several others.) Apparently coffee bars took hold rather recently in Taiwan and have become quite popular (often in combination with tea bars, but even as a thing unto themselves), although this was not so evident in the part of Hsinchu I was in.

It turned out that I spied this potentially nice coffee place right next (a few doors down from) to my hotel in Hsinchu, and one lunchtime I thought it would be nice to go and sit there and have some coffee. It was not clear whether the place really did sit-down coffee though, maybe only serving over the counter bulk coffee (no tables really set up… possible counter seat or two, but not really sure), and so I thought I would go in and do a bit of a mime to get across my question (as I’d grown accustomed to doing). So in I went, and the proprietor was chatting with someone over the counter. I thought I’d wait, but they broke off and I started to try to say something when the customer (a knock-you-over-the-head-with-a-bat-pretty young woman) spoke to me in English and so I asked her the question. So she asked the proprietor (a charming older lady with no English) and it was established that I could have a cup of coffee there for $100 NT and could sit. I tried to talk to the customer a bit more by asking her if she had a recommended coffee she liked, etc, but then we ran out of things to say before she had to run off, and that was it. She left. (I kicked myself for the rest of the day for not asking her if she wanted to join me for coffee, and wondered at the fact that I’d missed an opportunity to reach out and make a new friend. Getting slow in my old age, I guess.)

The proprietor took an awfully long time to make the cup of coffee, and I stood there on my own in the store, thinking that it would be really ironic if all of this resulted in a really lousy cup of coffee….

Eventually she brought it. It was excellent. It was in a rather special cup which she seemed rather proud of, and we had to fiddle a bit to set me up a table properly. (taking a large bag of beans off the only one that was close to flat on the floor and so usable). For the rest of the time I was there it was clearly a big deal that I was sitting and drinking coffee, for every time one of her regulars came in to get some beans, there was a long conversation, and then they would both turn and look at me for a moment, and then carry on talking. (Also, she came over and glanced over my shoulder at what I was writing, not knowing that I could see her doing this -I’ve eyes in back of my head, in case you are wondering-…..I was playing with a conjecture at the time and drawing lots of pictures and scribbling equations…wonder what she thought that all was?).

As you can see from the pictures, the place was very charming, as coffee places go. It turned out that this was typical of the dedicated coffee places (I went to others later, and in other cities). They’re just chock-a-block full of bags and bins of coffee, coffee paraphernalia, bizarre-looking coffee-extracting equipment (including lots of fancy round glass flasks straight from a science lab in a 1950s SF movie). It is an aspect of the atmosphere that I had not anticipated, and was rather welcome, since I’m quite a fan of ….paraphernalia.

Well here’s the more unexpected part of the story. Continue reading ‘The Search for Coffee’

Greetings from chilly Vancouver, where I’ve been visiting the University of British Columbia for the last few days. Besides breathtaking topography and amazing Pacific cuisine, a big advantage of the region is that you can’t swing a cat without hitting an atheist around here. That’s right: no religion was the largest reported “denomination” among B.C. residents, with more than twice the number of Roman Catholics, the second-biggest group. Thanks to Scott Oser for pointing this out.

(There don’t seem to be many Jewish people in B.C. I suspect that Moshe is the only one, and he was traveling during my visit.)

I have to admit, though, that I’m confused. People here seem relatively friendly, and there is quite an effective social safety net, including universal health care. Where did all this niceness and compassion come from, without God to tell them how to behave? I’m pretty sure that I’ve heard that godlessness leads to a selfish, cutthroat, me-first attitude, so much unlike the selfless regard for the less fortunate that characterizes our religious culture in the States. These Canadians are probably a bunch of backstabbing Enlightenment hedonists under their smiling facades.

Here’s another reason that I love working at a University with a broad spectrum of activity, in an exciting and diverse city. You get the most wonderful connections between different segments of your life:

After an extraordinarily exhausting week, Friday evening came and I jumped on the Brompton and cycled up Figueroa the 37 blocks to the heart of downtown, where you can find the music centre, and the wonderful Disney Hall. My errand was to somehow obtain tickets for an extremely popular concert. The box office, once I got there, had only a few returned ones, at $120 and $90 each. I could not bring myself to pay that much without exploring other avenues (I’ve several expenditures to worry about) and so I thought I would wait in case anyone turned in orchestra seats (those are more like $35), or to see if the price would drop nearer the concert start, or (my main hope) to see if someone showed up with an extra ticket (maybe a friend could not make it) and would just sell it to me right there near the box office. So I stood there for over an hour, watching the world go by, most of it looking curiously at my bike in half-fold position. It dawned on me at some point that I’d no really reliable way of discovering who might have tickets to sell or not. This became especially clear after a group of people who came well after me and were hanging around managed to get a ticket in this manner. So after a while I began to learn who had “the look” of maybe having a ticket to sell, and with about ten minutes to go before the concert (and after a long conversation about the bike which made me miss at least one more sale) I managed to negotiate an $82 ticket down to $50 (I could have done better, but it seemed fair), folded up and popped my bike off in the coat check area and emerged (appropriately attired) for an evening of a bit of relaxing to some Mozart.

I came because I had three students (Joesph Benson, Kyle Patterson and David Reese) in my Physics 151 tell me that they had to miss some parts of a few Thursday lectures because they had to go and rehearse for a concert. Of course, I asked what concert it was, and it turned out that they (as part of the USC Thornton Choral Artists) would be performing Mozart’s Requiem with the LA Philharmoic at Disney Hall over three nights! Of course I had to find a way to go!

Continue reading ‘The Singing Engineers’

Saw this in the Physics Department at National Central University in Jung-Li, Taiwan. A very right-thinking place indeed, to have the detail of a nice kettle on the door of the little kitchen down the hall.

I went there (on Wednesday 4th January, during my Walkabout) to give a lecture (”Non-critical Strings and Matrix Models”) with more background material on the matters in the seminar I presented a week and a half before in Taipei (the one before I dashed for the bus to Tainan…). It was at the invitation of Chiang-Mei Chen. There I also met Otto Kong Cho-Wing. They are both high energy physicists (Chiang-Mei is in General Relativty, while Otto Kong is a particle phenomenologist), and I enjoyed my short visit. (Relativists among you will know the name Nester. Well, the man himself, James Nester, is also part of the department there, although he was away at the time I visited.) Chiang-Mei and Otto Kong were excellent hosts, and particularly gracious (and visibly happy to relocate) when, after we sat down to lunch (and saw the menu) at a Western-style restaurant they clearly thought I would prefer, I quietly suggested that I had been looking forward to trying (hint! hint!) the Chinese-style one that they had briefly mentioned earlier. We left and went to the otherone, telling me that they preferred the Chinese-style one too. It was probably rude for me to have said anything, I know, but everyone got a much better meal out of it.

-cvj

…. I gave the midterm for my Electromagnetism class today. Stayed up until 1:30am putting the finishing touches on it, and then up again four and a half hours later to go in early and get it and its accompanying formula sheet (yeah, yeah, I’m getting soft, I know) photocopied, and ready to give to them at 8:45am in class. They had one hour of furious computing -and a bit of thinking- to do. These ones are hard to get right since you’ve got to gauge their ability to do enough in the short time allowed. Get it wrong (like I did with the equivalent mid term last year) and they just can require way longer to do it than they have time for. It is really important to recall that they are still young and don’t take all the same computational shortcuts that one does later in life. And recall that for upper-level courses I like to have a bit of fun new stuff in there too, so I had to think carefully about how to do that in one hour too. (The plan was to do this all with the aid of the atmostphere at the Cat and Fiddle, like last week’s midterm prep session, but in the end I got sucked in by several incredibly campy Queen videos -how come we never saw that aspect so clearly as kids?- on You Tube…., which made for a background which is more relevant than you think… more on that later.)

So it worked! And they (most of them I think) really liked it (at least a number said so immediately after, and they were all chatting happily about bits and pieces on the exam after they’d done….. which is good)… there did not seem to be that air of them having been treated unfairly that happens when an exam misses the mark. This is easier with 12 students, than say, the 250+ freshmen I (and my colleague) set a midterm for last week. That one went ok, but was actually too easy, and now we have to alert the students to the fact that they should not feel overly confident about how they are doing….

For my E+M midterm today, it was just right, and as a bonus I think they learned something about superconductors and superconducting rotating spheres and the Meissner effect… oh, and why the electron is not a tiny rotating classical spherical shell of charge, which everyone should know, of course. So what’s not to like? (as they say).

-cvj