Interesting experiment reported in Science, “Mesoscopic Phase Coherence in a Quantum Spin Fluid,” Xu et al (available here). The authors discuss a one dimenionsional spin chain where each site has a spin 1 system. This system is coupled antiferromagnetically to its nearest neighbor. Now such systems have a ground state whose two spin correlation, [tex]$langle S_i S_j rangle[/tex] decays exponentially as a function of the distance between site i and site j. However, if you examine the more complicated correlation function [tex]$langle S_i exp [ i pi sum_{i<k<j} S_k]S_j rangle[/tex] this tends to a constant as the distance between the two sites increases. Thus a more complicated order exists in this system, one which is not revealed by a simple two spin correlation function (In this traitorous world, nothing is true or false, all is according to the color of the crystal through which you look.) This order is known as a string order. In particular the ground state of the system is roughly a superposition over Neel states (over [tex]$S_z=pm 1$[/tex]) with [tex]$S_z=0$[/tex] inserted into these states. The amplitude of each of these states in the superposition is exponetially decreasing in the number of inserted $S_z=0$ states.
Okay, cool, so there is this nice model which has a very cool ground state whose order isn't in a two spin correlation but some other, more interesting order. But what is cool about this experiment is that the authors are able to examine the excitations in this system. In particular they examine the creation of a triplet pair excitation at rest and show that these propogate over a fairly large distance before losing their coherence (roughly fifty lattice units.) Indeed, if I am reading the article correctly, it seems that this coherence is limited only by the length of the chains themselves (at low temperature, at higher temperature thermal excitations can shorten this coherence length.) Cool! This, I think, should give hope to those who are interested in using spin chains for quantum computation, although, of course, TIALWFAQC (this is a long way from a quantum computer.)
Kielpinski Spaces
Reading Light
So at the begining of the book a main character kills a guy and returns to a lab (of course, doesn’t everyone go to lab after they’ve murdered someone?) where they are working with “q-bits” [sic]. Then this choice line (p.6):
“We can slow down the rate at which the q-bits pick up phase. We’re actually doing better than Kielpinski there – I’ve had factors of four and up this week.”
Despite the Cornell spelling (it’s so cold in Cornell that David Mermin loses the “u”?), cool! Hopefully, many of you will recognize the reference to Dave Kielpinski who did some amazing ion trap quantum computing experiments at NIST and is now at Griffith in Australia. Okay cool, a reference to a real quantum computing researcher.
But it gets better! A few lines later:
Somewhere off in its parallel mazes, the Beowulf system begam modelling the decoherence-free subspaces – the Kielpinski space – of an ion pair…
Not only q-bits [sic] but also decoherence-free subspaces (no subsystems, alas)! And indeed this is a direct reference to papers Kielpinski was involved in: “A decoherence-free quantum memory using trapped ions,” D. Kielpinski, V. Meyer, M.A. Rowe, C.A. Sackett, W.M. Itano, C. Monroe, and D.J. Wineland, Science 291, 1013 (2001) and “Architecture for a large-scale ion-trap quantum computer,” D. Kielpinski, C.R. Monroe, and D.J. Wineland, Nature 417, 709 (2002). That former paper saved my butt during my thesis defense. An AMO physicist, about half way through my defense, said something like “Well this theory is all good, but what about in the real world.” My next slide was a plot yoinked from that first paper showing the first experiment which demonstrated slower decoherence in a decoherence-free subspace under ambient conditions.
And, dude, from now on I am totally calling the DFSs in ion traps “Kielpinski spaces.”
Onion Laugh
Vatican Apologizes For Torture, Murder Of Stephen Hawking. I’ve seen his talking wheelchair. It says “beep! beep! beep!” often during the middle of his own scientific talk.
The Casinos Must Love This….Or Do They Hate It?
A New York Times article on computers playing poker heads up against humans opens with
For anyone stuck on a casino stool, playing hours of video poker, rest assured: humans can still beat a computer.
Um, well first of all, video poker is quite different from the heads up Texas Holdem the entire article is about. Significatly different from an artificial intelligence standpoint. Second, as far as I know, video poker machines have payoffs for an optimal strategy which are usually right around equal payoff and hourly wages you’d get from playing this strategy are pretty pathetic even for the machines with greater than even payoff. Since the majority of players are probably far from an optimal strategy, I’d guess video poker is quite the cash cow for the casinos.
But I wonder, when computers finally are able to beat humans at a poker (okay, some will say, “never!” I will say, you’re allowed to say “never” when you can run a thousand body simulation of a star cluster in your head. Reverse Turing Shazam!) whether this will actually hurt video poker machines. Hm, well seeing how they casinos still seem to rack in the mullah with their slot machines, probably not.
Random Paper
A new paper, “On the Generation of Random Numbers.” Postscript available here. What do you think should I submit it to the arXiv?
Daydreaming About Storytelling
I have always been a daydreamer. There isn’t a place or distraction in the world which can keep me from somehow drifting off into a daydreaming state of mind. Which, of course, must be rather amusing for others observing my behavior. One second I’m talking about Barry Bonds and the San Francisco Giants, and the next second I’ve got black holes in my eyes and am in full monk mode. Daydreaming is definitely the appropriate expression, since rousing me from this state is a lot like trying to wake me up: not an easy task!
So what do I think about when I’m in daydream mode? Well mostly I tell myself stories, or think about how things fit together. Now these stories definitely aren’t page turning blockbusters, they’re mostly about a problem I’ve been working on. Mentally it feels like I am constructing possible stories of how this or that problem might be resolved. Knowing X what does this imply about trying to make progress on problem P. Does it imply Y? Is Y consistent with a solution to P? Does Y fit into the story I know about problem Q? Etc. Etc.
Which leads me to the following question. How much does storytelling shape “good” thinking? (Okay, so my thinking is mostly less than “good”, but every once in a while I’m not a dufus.) For many years I’ve wondered how it might be possible to teach a class, like say, introductory mechanics (yeah I’m still a physicist at heart, you know), which teaches the physics by tracing the history of the subject. (I told this idea to some faculty well versed in physics education when I was a grad student and you should have seen them recoil in horror 🙂 ) Now, however, I’ve come to think that this desire was a misplaced projection. What I really wanted to figure out how to do was how to teach a course where the students could build up their own consistent story of what was going on. This story, of course, must be routed in all the history of the subject: you too must come to realize the trials and tribulations which led people to believe what they do. But it isn’t necesarily a history centric endeavor, but is more squarely centered on thinking up your own story. And it has got to be a story you are constantly examining and checking, i.e. which is open to repeated examination for consistency. A story which you could come to by daydreaming.
Another piece of anecdotal evidence of the role of storytelling in sharp thinking comes from my undergraduate days. When I think about my years at Caltech, one of the most fascinating events I observed was to watch those super achieving students spin yarns. It was not uncommon to spend hours at a time, taking some departing idea and then spend hours working out the consequences of this idea. Sure, some would call this simple B.S.ing and often the point of departure involved a Simpson’s episode, but in retrospect, I think that this was a great indication that deep down in these students brains, they had built up a strong consistent storytelling mechanism for thinking.
So what role does storytelling play in shaping sharp minds? Of course, I don’t know, but I’d love to hear a story which lets me understand how storytelling fits in with how our brain works. Then I could daydream about it.
[Of course this post is a grand exercise in extralusionary intelligence, for there are certainly loads of educational data on the role of storytelling in education. A quick look this morning, however, didn’t turn up anything concrete. So like any ignoramus, I’ve written this post completely unaware of the story other, more savy, researchers have been able to peice together.]
Dude, a Higs Boson?
Best quote from an article in the New York Times about the search for the Higgs boson:
Joe Lykken, a Fermilab theorist who said he first learned of the rumored bump the old-fashioned way, over lunch in the laboratory cafeteria, said: “Pre-blog, this sort of rumor would have circulated among perhaps a few dozen physicists. Now with blogs even string theorists who can’t spell Higgs became immediately aware of inside information about D Zero data.”
Zing!
I’m also very jealous of Gordon Watts, a fellow University of Washington blogger:
In response, Gordon Watts, a physicist from the University of Washington and longtime member of the D Zero team, scolded Dr. Dorigo for speculating on rumors.
“Dude! If you get called by the press to comment on this rumor — you will be making secondhand comments on rumors!” Dr. Watts wrote on his blog, Life as a Physicist.
Why am I jealous? Because he just got quoted in the New York Times, the paper of record, as saying “Dude!” Dude that rocks.
Turducken?
Juiciest paper on the arxiv yesterday? 0707.3101: “Excision Without Excision: the Relativistic Turducken” by D. Brown, O. Sarbach, E. Schnetter, M. Tiglio, P. Diener, I. Hawke, D. Pollney.
Helen Lavender Bacon, 1915-2007
Yesterday my grandmother, Helen Lavender Bacon passed away at the age of 91. Grandma Pete (as we called her, Pete being my grandparent’s dog…doesn’t everyone name their grandparents after their grandparent’s pets?) was the kindest person I have ever met in my life. I have many fond memories of my grandma, including a spectacular trip I took with my father to visit her and my grandpa in Sacramento where I got to see my dad argue a case before the California Supreme Court and woke up during the return trip on a small airplane staring directly at Mt. Shasta, but mostly I will remember standing in line with my grandma. Standing in line, you say? Pft, what a silly memory! But what you have to understand is that if you would go out to a grocery store with my grandma, and were waiting in the checkout line with her, random strangers would, unprovoked, start up conversations with you. There was something in her smile, in her body language, which just invited people into conversation. As if you could just tell that she was going to be fun to talk to and always smile at your jokes and your ideas. Whenever I see kindness, a part of my thoughts will always remember my grandmother, and standing in line.
Here is my Grandma Pete, only a few years ago, riding on the wild side:
From the Sacramento Bee:
BACON, Helen Lavender
Passed away peacefully on July 18, 2007 at age 91 in Carmichael, CA. She was preceded in death by her loving husband of 60 years, Glenn Claire Bacon and beloved son, Larry George Bacon. She is survived by son, Glenn Charles Bacon; nieces, Doris Adams and Helen Jensen; six grandchildren and three great-grandchildren. She will be deeply missed by her family and friends. Helen was born on September 11, 1915 in Hyattville, WY. She was raised in Washington state and Arizona where she was married to Glenn and gave birth to her sons. She moved to the Sacramento area in 1947 and has been a resident here since. Over this time, she has been blessed to have a huge community of caring friends who have been most kind and giving in her aging process. A celebration of Helen’s life will be held at Celtic Cross Presbyterian Church, 5839 Dewey Dr., Citrus Heights, Saturday July 21 at 1:00pm. Private interment will be at Sierra Hills East Lawn Memorial Park. Helen (Mom, Grandma) was a source of loving kindness for everyone she touched. In lieu of flowers, an appropriate remembrance would be an intentional act of kindness on her behalf.
Published in the Sacramento Bee on 7/19/2007.
Many Universes, But Not All Lead to Salvation or the Simpson's Movie
It
[youtube]http://youtube.com/watch?v=OL50ddCSJmo[/youtube]
is
[youtube]http://youtube.com/watch?v=q-O7Nteshv4[/youtube]
coming!
[youtube]http://youtube.com/watch?v=3r-YJOrY28w[/youtube]
Maybe, finally, after all these years of waiting, we will learn just exactly what “Quantum Presbyterianism” is:
Homer: [opens door to find Kang and Kodos standing there] Hello — oh great. Mormons.
Kang: Actually, we’re Quantum Presbyterians…
I’m thinking it involves a doctrine which says that you are spiritually doomed to branches of the wavefunction which are condemned by God, but the divine intervention of God can lead you to those branches which are not condemned. Or something like that.
“Spider pig, spider pig…”