Right now I’m at my office, but I’m also vacuuming my home. How am I doing this, you ask? My new Roomba – the robotic vacuum! Already I am thinking of new names for my new robotic friend. This will be needed especially when the Roomba accidentally (can a robot do someting “on accident?”) chews up something it wasn’t supposed to chew up. The coolest thing about the Roomba right now is that when it gets low on power, it returns to its charging station. Now if only it could reproduce…
Four Pages
Recently I have been debating in my head the following question: Does the four page limit for papers in Physical Review Letters squash physics?
Benefits of the four page limit: (1) brevity enforces a focused article, (2) experiemental results can often be described in four pages, (3) you can tell when a paper is submitted to PRL on the preprint server by counting the number of pages.
Problems with the four page limit: (1) brevity means much is left out or compressed to near unreadability, (2) experimental techniques are rarely described in enough detail, (3) the compression to unreadibility means that general readership across the different sections of PRL, one of the supposed goals of the journal, is difficult if not impossible, (4) the papers are often light on citations since it is easier to cut citations to get to the page limits than to cut the content, (5) theories of any complexity are impossible to present in four pages without obmitting or skimming major portions of the work.
Physics and Engineering
This opinion article in Nature (433, 179 (2005)) is a bit rambling, but still very interesting.
Einstein is dead
Until its next revolution, much of the glory of physics will be in engineering. It is a shame that the physicists who do so much of it keep so quiet about it.
Once upon a time there was (and still is) a multinational manufacturer of sheet metal whose researchers realized they could improve the reliability of its production processes. By solving the equations of heat transfer for the company’s rolling presses, and testing the solutions on scale models, they significantly reduced the margin of error in the thickness of the rolled sheet. Their prime customer, a manufacturer of metal cans, was delighted. Millions of pounds were saved in materials and rejected products, and (maybe) the reduced costs were passed on to the customer. Maybe, too, the physicists got bonuses.
How very far removed from the special theory of relativity and the world of quantum mechanics — the parallel revolutionary paradigms on which most of twentieth-century physics and related technologies were based. Now, 100 years after Einstein’s first pioneering papers in those disciplines, physicists worldwide are rightly going to town, with conferences, artistic commissions and games… They are doing their utmost to celebrate in the face of the relentless promotion of biology as the exciting science of the current century and despite declining interest in physics amongst the young.
Einstein is not only the patron saint of physics but also an icon of integrity and scientific pursuit for its own sake — and, for the wider public, an appealing elderly gentleman. Small wonder, then, that UK and Irish physicists opted to call 2005 ‘Einstein year’, rather than the ‘Year of physics’. But Einstein is long gone. His ideas, his style and his legacy still inspire, but his rejection of the quantum picture of reality and his dreams of the unification of forces have been replaced by the acceptance and exploration of quantum entanglement and highly esoteric (albeit potentially profound) attempts to derive twentieth-century laws from a deeper paradigm for the structure of space-time.
To hang a ‘Year of physics’ so centrally on Einstein is to miss the key lessons of the metal manufacturer: that physics is not only central to our understanding of the Universe (just what are dark matter and dark energy?), but is also central to making useful and sometimes inspiring things. Sheet metal is at the more prosaic end of the spectrum. At the other end, Steve Jobs, head of Apple, said at last week’s launch of the latest iPod: “Most people make the mistake of thinking design is what it looks like… Design is how it works.” In other words, sexy design is also about sexy engineering and the sexy science behind it.
And listen to theoretical physicist Michael Berry of the University of Bristol, UK, launching the competition “Physics for taxi drivers” (Physics World December 2004, p. 15; http://physicsweb.org/articles/world/17/12/2 ).He recalls how a description of a CD player and a satellite navigation receiver convinced a cab driver that physics is interesting. The worry is not so much that people cannot understand the relevance of physics — and credit to the ‘World Year of Physics 2005′ organizers for a poster competition for 10–16-year-olds to celebrate that. The worry is that in universities, and especially in schools, there is so little emphasis and imagination, either this year or ever, in celebrating physics’ relevance and, more importantly, sending the right career signals to young people.
Many young people today are as capable as previous generations of being inspired by the challenge of making things: engineering with unbelievable precision in the face of quantum uncertainties, creating elegance in functional design, and delivering innovative and useful — or even socially transforming — everyday things. Nature’s pages have included their share of the foundations of twenty-first-century manufacturing, with advances in the quantum control of atomic and molecular states, quantum information and optoelectronics.
Some of the authors of those papers have interesting engineering careers ahead of them. As surveys by learned societies repeatedly show, a large proportion of physics graduates find fulfilling and well paid employment in engineering and information technology. Those same societies, and governments and physicists generally, repeatedly fail to get that message across to the public or to kids in schools. Yet that is surely a more important challenge this year than reiterating in depth, appropriately but ineffectually, that Einstein was great.
Somedays, as a quantum information science researcher, I want to shout to physics and computer science departments: “Look at us! We are a legitimate intellectual pursuit!” It’s nice to see Nature doing the yelling for a change.
Alphabet Selection
Writing a grant today, I was listing all of my collaborators and noticed something strange. Three of my collaborators last names start with “B”, four with “C”, two with “D” and the only other letter which is duplicated in the rest of my collaborators are two “L”‘s. Basically all my collaborators last names are scrunched towards the front of the alphabet. So the question is: why this is so?
One observation which I don’t think holds for my collaborators is that it may be advantageous in a scientific career to have a last name which is early in the alphabet. Early in the alphabet means you are more likely to be first author, and because there is little standardization about what being first author means, this implies that you will pick up more first authorships than normal. And maybe this counts down the road (here you’re supposed to imagine evil tenure committee’s putting sand on a scale for every first and not first authorship!) But I don’t think it holds for my collaborators: none of us have been working long enough for such selection effects to take us out (as far as I know, that is!)
This reminds me of one of my footnotes which appears in this paper on quant-ph. The authors on the paper are listed as Carlton M. Caves, Christopher A. Fuchs, and Pranaw Rungta, in that order. However there is a footnote
The author ordering on this paper is dictated by CAF’s adherence to alphabetical ordering. CMC, operatoring under equally valid, but less strongly held principles, would have preferred, in this case, inverse alphabetical ordering.
Young Einstein
The nice thing about this New York Times article about the Einstein and the World Year in Physics, is that they provide a picture of Einstein when he was rather young. Isn’t it strange how the picture of Einstein many of us have in our head–the picture many of associate withe genius–is of the older Professor Einstein, and not of the young man working in a patent office?
Many argue that today no one “working in a patent office” could produce the same quality papers as Einstein did in 1905. But I doubt this. Maybe it’s because I still believe that our next fundamental breakthroughs in physics will be both revolutionary and simple. I guess this sits me on the opposite side of much progress in theoretical physics, which has seen a progressive increase in the level of sophistication, from special relativity to quantum theory to general relativity to quantum field theory to the standard model to superstring theory. But I’m a sucker for simplicity, and especially for conceptual simplicity. There are many ideas which are conceptually simple, but whose consequences are very difficult to sort out. And if it’s a simple idea with deep consequences which leads to the next new set of ideas in physics, then why can’t it come from someone passionate who isn’t sitting behind the standard academic bandwagon?
Quantum Gravity from Quantum Computation
In a paper sure to stir up some controversy, Seth Lloyd has posted a paper “The Computational Universe: Quantum Gravity from Quantum Computation.” on quant-ph.
Improv and Smart Lunches
Anyone who has seen good improv must immediately wonder how it is that the actors are able to pull of their trade of theater without preset form. One of the key tenets of improv is the notion of “acceptance.” The basic idea is that when carrying out dialogue one should accept what the other person says and not contradict it. Contradiction will quickly lead one down to a dead-end. You should take what the other actors are saying and make something of it.
When I first read about this doctrine of acceptance in improv I was immediately sure that I’d witnessed this before. Where? While having lunch with groups of scientists. When you get the right combination of smart people together, one of their favority pasttimes is constructing dialogues where someone says something like “wouldn’t it be interesting if….?” and then the rest of the group takes up this “if” and simply goes with it. And if you get a really smart group of people together these rides can be among the funniest and most interesting conversations you will ever have. I noticed this effect quite a lot as an undergraduate at Caltech: students would simply sit around and B.S., but they would B.S. in this very strange manner of accepting something and then taking it further and further with each person accepting the previous idea and pushing it even further.
So, while the stereotype says scientists are barely capable of dialogue (and this is certainly not far from the truth for many in everyday conversation), I would claim that scientists are also among the most versatile improv actors in the world.
Can Time be Measured in Bits?
Every living thing follows along a set path. And if you could see your path or channel, then you could see into the future, right? Like err… that’s a form of time travel. – Donnie Darko
Time is nature’s way to keep everything from happening all at once. – John Archibald Wheeler
The past exists only as recorded in the present.
What is time? This question, in various forms, has been pondered by physicists and philosophers for eons. No doubt, various advances in our understanding of time have been made (the relativity of time for different observers, the symmetry breaking of time invariance as demostrated directly by K^0-K^0-bar experiments, etc.) but there are still enough troubling aspects of time for a good theoretician to get lost in. For example, the role of time in quantum theory (and in particular in a theory of quantum gravity) is one question which has consumed the soul of more than a few physicists.
In physics, a question which often bothers theoreticians is the origin of an arrow of time. The problem roughly is that we have underlying laws which are time symmetric, yet the universe seems to pick out a particular direction for the evolution in time. One explanation for the arrow of time is that it comes from thermodynamics. If we start with a universe which has a very low entropy, then the forward march of time can be marked by the upward increase in entropy. If we had started in a universe with maximal entropy, presumibly there would be no advance of time. But if the increase in entropy corresponds to an increase in the forward direction of time, does this mean that we can measure time in the same units of entropy? Can we measure time, then, in bits?
At first sight, this seems wrong. Take, for example a reversible computer. This computer acts according to reversible rules and so the entropy of the computer does not increase, even though, time is increasing as the computer runs a program. But maybe there is a way out of this puzzle. One possibility is that it is impossible to construct a truely reversible computer. This might seem silly, since we think the laws of physics are reversible, and so we can think about some physical system as enacting a reversible computation. But it’s not clear to me that robust computation is possible with a totally reversible system (more specifically without some effective irreversibility, such as cold ancilla bits which are discarded.)
Another possibility is that it might be true that a reversible computer can be constructed, but that it is impossible to construct a clock without irreversible evolution. I.e. to see the evolution of a reversible computer with respect to time, we need a clock around. Here things get rather tricky. Can’t I can think of a simple reversible two state system which simply cycles between the two states as a clock? I don’t think so. The reason is that a clock isn’t really just a system which counts, but it’s really a way in which we callibrate the basic units of time. So I use a cesium atom as a clock by using it to calibrate what a second is. Thus I run an experiment which performs measurements on the cesium clock which gives me a basic calibration upon which all clocks can be run. But why can’t this callibration be made totally reversible? I’m not sure, but it’s a good homework problem. I suspect that the callibration experiement cannot be made reversible (whenever I try the simple methods to make it reversible, I run into “effective” irreversibilities.)
So it seems that we can measure time in bits, or at least thermodynamic time in bits. What about other arrows of time (such as the arrow of time arrising from K^0-K^0-bar experiments or a cosmological arrow of time?) It would be fun to try and design a K^0-K^0-bar experiment which acts as a clock. And what of the relationship between time being measured in bits and the holographic principle, where surface areas are measured in bits?
See I told you a theoretical physicist could lose his soul thinking about time.
SQuInT 2005
The schedule for the seventh annual SQuInT workshop is now online:
Friday Feb. 18
7:30-8:25 Breakfast (provided)
Session 1: Ion Traps
8:25-8:30 Welcome
8:30-9:00 Chiaverini, “Simple algorithms implemented in a scalable trapped-ion quantum processor”
9:00-9:30 Berkeland, “Quantum simulations with trapped strontium ions”
9:30-10:00 Morning Break (provided)
Tutorial:
10:00-11:00 Chuang, “Lessons from NMR for quantum computation”
Session 2: Quantum Information Theory
11:00-11:30 Bacon,”Optimal measurements for the dihedral hidden subgroup problem”
11:30-12:00 Gurvits, “Convex geometry of quantum entanglement”
12:00-2:00 Lunch (provided)
Invited Talk:
2:00-2:45 Steane, TBA
Session 3: Quantum Measurement and Signal Processing
2:45-3:15 Williams, “Quantum signal processing”
3:15-3:45 Afternoon break (provided)
3:45-4:15 Silberfarb, “Quantum state reconstruction via continuous measurement”
4:15-4:45 Geremia, “Optimal discrimination of optical coherent ctates using feedback control”
4:45-5:15 Hawley, “Nondemolition measurement of single spin state for quantum computation based on optically detected magnetic resonance”
6:00-7:30 Poster session
7:30- Dinner (on your own)
Saturday Feb. 19
7:30-8:30 Breakfast (provided)
Session 4: Quantum Communications 1
8:30-9:00 Hughes, “Quantum key distribution in optical fiber networks”
9:00 -9:30 Raymer, “Engineered pure-state single-photon wave-packets”
9:30-10:00 Morning Break (provided)
Tutorial:
10:00-11:00 Spekkens, TBA
Session 5: Fault Tolerance
11:00-11:30 Szkopek, “Threshold error penalty for fault tolerant computation with nearest neighbour communication”
11:30-12:00 Eastin, “Fault tolerance for restricted error models”
12:00-2:00 Lunch (provided)
Invited Talk:
2:00-2:45 Schoelkopf , TBA
Session 6: Solid State and Electronics
2:45-3:15 Gibbs, “Vacuum Rabi splitting with a single quantum dot in a photonic crystal nanocavity”
3:15-3:45 Goodkind, ” Progress fabricating qubits using electrons on helium”
3:45-4:15 Afternoon break (provided)
4:15-4:45 Waks, “Cavity-waveguide interaction in photonic crystals”
4:45-5:15 Guney, “Implementation of entanglement and quantum logic gate operations using three-dimensional photonic crystal single-mode cavity”
5:15-5:45 Yao, “Design of solid-state nanodot-cavity-waveguide system for quantum computation and quantum information processing”
7:00- Banquet
Sunday Feb. 20
7:30-8:30 Breakfast (provided)
Session 7: Cold atoms
8:30-9:00 Lev, “Magnetic microtraps for cavity QED, BECs, and atom optics”
9:00-9:30 Chou, “Storage time of a quantum memory in an ensemble of cold atoms”
Invited:
9:30-10:15 Molmer, TBA
10:15-10:45 Morning Break (provided)
Session 8: Quantum Communications 2
10:45-11:15 Sanders, “Remote entanglement distribution”
11:15-11:45 Wodkiewicz, “Fidelity of noisy quantum channels”
11:45-12:15 Spedalieri, “Exploiting the quantum Zeno effect to beat photon loss in linear
optical quantum information processors”
What I love about SQuInT is that (1) there are both theory and experiment talks and (2) having gone to all of the SQuInTs except the pre-SQuInTs, I get to witness the slow stead experimental progress in building a quantum computer.
Die Comment Spam Die!
Having gotten sick of dealing with all the comment spam I’ve added a plugin which makes you enter a random code when posting comments. Sorry for the inconvenience.
Update: Well it looks like I’ve broken the comments. Will try to fix tonight.
Update: Fixed. Let me know if anyone is seeing anything strange (beside my ugly mug, of course.)