Three greats who we’ve lost
Sir Charles Antony Richard Hoare (1934-2026) won the 1980 Turing Award for numerous contributions to computer science, including foundational work on concurrency and formal verification and the invention (with Dijkstra) of the dining philosophers problem. But he’s perhaps best known, to pretty much everyone who’s ever studied CS, as the inventor of the Quicksort algorithm. I’m sorry that I never got to meet him.
Michael O. Rabin (1931-2026), of Harvard University, was one of the founders of theoretical computer science and winner of the 1976 Turing Award. In 1959, he and Dana Scott introduced the concept of a “nondeterministic machine”—that is, a machine with exponentially many possible computation paths, which accepts if and only if there exists an accepting path—which would of course later play a central role in the formulation of P vs. NP problem. He’s also known for the Miller-Rabin primality test, which helped to establish randomness as a central concept in algorithms, and for many other things. He’s survived by his daughter Tal Rabin, also a distinguished theoretical computer scientist. I was privileged to meet the elder Rabin on several visits to Harvard, where he showed me great kindness.
Sir Anthony Leggett (1938-2026), of the University of Illinois Urbana-Champaign, was one of the great quantum physicists of the late 20th century, and recipient of the 2003 Nobel Prize for his work on superfluidity. When I knew him, he was a sort of elder statesman of quantum computing and information, who helped remind the rest of us of why we got into the field in the first place—not to solve Element Distinctness moderately faster, but to learn the truth of quantum mechanics itself. Tony insisted, over and over, that the validity of quantum mechanics on the scale of everyday life is an open empirical problem, to be settled by better experiments and not by a-priori principles. I first met Tony at a Gordon Research Conference in southern California. Even though I was then a nobody and he a recent Nobel laureate, he took the time to listen to my ideas about Sure/Shor separators, and to suggest (correctly) what we now call 2D cluster states as an excellent candidate for what I wanted. In all my later interactions with Tony, at both the University of Waterloo (where he was visiting faculty for a while) and at UIUC (where my wife Dana and I considered taking jobs), he was basically the friendliest, funniest guy you could possibly meet at his level of achievement and renown. I was bummed to hear about his passing.
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