Author: dabacon

Sad news comes from via Lance Fortnow’s Computational Complexity:

Asher Peres, 1934-2005
By Netanel Lindner, Petra Scudo and Danny Terno via Christopher Fuchs
Quantum information science lost one of its founding fathers. Asher Peres died on Sunday, January 1, 2005. He was 70 years old.
A distinguished professor at the Department of Physics, Technion – Israel Institute of Technology, Asher described himself as “the cat who walks by himself”. His well-known independence in thought and research is the best demonstration of this attitude. Asher will be missed by all of us not only as a great scientist but especially as a wonderful person. He was a surprisingly warm and unpretentious man of stubborn integrity, with old-world grace and a pungent sense of humor. He was a loving husband to his wife Aviva, a father to his two daughters Lydia and Naomi, and a proud grandfather of six. Asher was a demanding but inspiring teacher. Many physicists considered him not only a valued colleague but also a dear friend and a mentor.
Asher’s scientific work is too vast to review, while its highlights are well-known. One of the six fathers of quantum teleportation, he made fundamental contributions to the definition and characterization of quantum entanglement, helping to promote it from the realm of philosophy to the world of physics. The importance of his contributions to other research areas cannot be overestimated. Starting his career as a graduate student of Nathan Rosen, he established the physicality of gravitational waves and provided a textbook example of a strong gravitational wave with his PP-wave. Asher was also able to point out some of the signatures of quantum chaos, paving the way to many more developments. All of these contributions are marked by a surprising simplicity and unbeatable originality.
Of all his publications, Asher was most proud of his book Quantum Theory: Concepts and Methods. The book is an example of Asher’s scientific style: an uncompromising and deep understanding of the fundamental issues expressed in a form which is as simple and accessible as possible. It took Asher six years to carefully weave the threads of his book together. The great quality of the work is acknowledged by anyone acquainted with the final result.
In a favorite anecdote, Asher told about a reporter who had interviewed him on quantum teleportation. “Can you teleport only the body, or also the spirit?” the reporter had asked. “Only the spirit,” was Asher’s reply. Our community has been privileged to know him and have been touched by his spirit.
I am the cat who walks by himself is a charming twelve-page autobiography covering his life from his birth in the village Beaulieu-sur-Dordogne in France until his meeting with Aviva on a train to Haifa. The rest of his story is in his formal CV.

Asher’s book, besides being a classic on foundational issues, profoundly influence much of the style of today’s quantum information science. One passage in particular was a favorite of mine which I accidentally quoted to Murray Gell-Mann the other day:

This mental prcoess can be repeated indefinitely. Some authors state that the last stage in this chain of measurements involves “consciousness,” or the “intellectual inner life” of the observer, by virtue of the “principle of psychophysical parallelism.”[3,4] Other authors introduce a wave function for the whole Universe[5]. In this book, I shall refrain from using concepts that I do not understand.
[3] J. von Neumann, Mathematische Grundlagen der Quantenmechanik, Springer, Berlin (1932) p. 223; transl. by E.T. Beyer: Mathematical Foundations of Quantum Mechanics, Princeton Univ. Press (1955) p. 418
[4] E.P. Wigner, Symmetries and Reflections, Indiana Univ. Press, Bloomington (1967)

Among all the papers which Asher wrote, I think my favorite would have to be a paper he wrote with Wootters: “Optimal Detection of Quantum Information,” Phys. Rev. Lett. 66, 1119-1122 (1991):

Two quantum systems are identically prepared in different locations. An observer’s task is to determine their state. A simple example shows that a pair of measurements of the von Neumann type is less effective than a sequence of nonorthogonal probability-operator measures, alternating between the two quantum systems. However, the most efficient set of operations of that type that we were able to design falls short of a single combined measurement, performed on both system together.

Particle physicists have always considered themselves the kings of physics. Murray Gell-Mann famously called solid state physics by the moniker “squalid state physics.” In the ivory towers where scientists picture themselves as selfless serfs in the service of knowledge, particle theorists have long occupied the attic. At the same time, there is another community of the mathematically inclined who claim that they do their work for the greater good of knowledge: programmers. In particular the open source spirit of programming, that good code is in some way eternal and should be shared and contributed to the greater cause, gives good coders an air of superiority not dissimilar to that found in particle theorist.
And when I think about these two fields, I begin to think that perhaps quantum computing is today’s version of the selfless king in search of knowledge. Not only are we learning about the fundamental ways in which quantum information and computation differs from classical information and computation, I think many of us in the quantum computing community also feel that our work will have some greater consequence once a quantum computer is eventually built. We are, therefore, I think a rather smug community not very dissimilar to particle theory or the ethic of the eternally beautiful algorithm. Whether this smugness will be our undoing, our triumph, or our own psychosis with which we will beat ourselves over the head is another question.