Quantum Algorithms
Tuesday, March 08, 2005
Eugene Wigner
When I was a kid, my uncle told me a great story from his freshman year at Princeton about a brilliant physicist who gave a guest lecture on diffraction. I couldn't remember who it was or what the details of the story were, so I asked him to email me the story:

The person who gave the lecture was Eugene Wigner, who a few months earlier, in 1963, had received the Nobel Prize. We knew that Wigner was going to give the lecture and we were anticipating it. When we entered the big old lecture hall, there was a pleasant looking, older gentlemen holding the door open for us. It didn't hit us at first who that man was, but that was the way that he wanted to introduce himself to us. Damned, pure genius looked like a guy that you would expect to see sipping coffee in a Viennese cafe. Pleasant as can be, unassuming, smiling pleasantly to each person as we passed by.

There were two large blackboard spaces that had two blackboards in each space, one forward and one behind. A lecturer could write on a blackboard and then save the writing by pushing that board up and hauling the other one down to continue the writing. Wigner had a hard time handing this set up. "Where did I write that?" "How does this work?" Which one should I write on first?" Practical problems like that. There was also a string that hung down in the middle of this confusing apparatus, that could be used to manually lower the projector screen. This last complication and visual interference was particularly troublesome and a source of continual irritation as equation were developed on either side of the string, sometimes causing the equation to be divided, not at the equal sign, but at an inconvenient place in the expression.

However, Wigner was still able to focus sufficiently to do things that I have never seen before or since. We knew that Wigner had developed the math Fermi needed to develop the first nuclear reactor (the "Pile" of carbon neutron moderator, boron neutron absorber, and uranium neutron producer and gama ray - energy- generator, that would be critical, but not supercritical, which is an exponential power spike that potentially could have quickly changed the configuration and location of that nice pile that was under the sports stands at the University of Chicago)

Wigner said that he had accepted this teaching challenge though he had no recollection of exactly what the phenomenon was when light when through space occupied with matter. Never the less, he accepted the assignment. He brought a dictionary which he used to look up "Diffraction", though, as I recall, he had as much trouble coming up with the correct spelling as I just had. He read the definitions, though he had to think for a while about which definition he should us--that had the promise to lead to clarifying the phenomanon, not confuse us, and no doubt him, further. "Ah hah", in that good-humored German accent, "this is the von to use". We were all thinking OK, if you say so.

Wigner started to crank out the equations, everything with triple integrals and more Greek letters than frat row, all written in a hand that made all of them look kind of similar, all like a variation of "Q". As he approached the end of his allowable space on the fourth black board he began to slow down and a scowl crossed his face. In mid equation he stood back and said "This cannot be right. Something is wrong." His hand passed over the equations, starting back from his last equation. He went back a few equations, then he slowly stood back from the board, pointing, and said, "That's it. That is the mistake." He erased the now obvious (to him) error, changed the appropriate place in the subsequent equations, and finished the last equation. He turned to us in the audience, a slow grin broke out on his face, and he said in a quiet manner, "That makes sense."

No one said anything. We were all trying to appreciate the moment and to store it in our long-term memory. We broke out in a respectful applause, not too much so we wouldn't embarass this sensitive man. We were a classroom of freshmen engineers, so an appreciation or understanding of the material presented to us was not possible for any of us. But we could appreciate seeing how a mind in tune with nature translates observation and logic into a mathematical model

Wigner flushed a little, bowed slightly, went to the door and held it open for us as we filed out, a little dazed, heading for our next class which had no hope of holding us enthralled as Mr.Wigner had.

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