Blog Archive: 2010

Recent Progress in Quantum Algorithms


Dave Bacon, who wrote the elegant overview of the research discussed in my New Year’s Day post, just published his review, joint with Wim van Dam, of Recent Progress in Quantum Algorithms. Bacon writes beautifully, and this piece is no exception.

Most people have heard of no more than two quantum algorithms: Shor’s factoring algorithm and Grover’s search algorithm. For five years after Grover’s algorithm, no one discovered a significantly novel quantum algorithm, only variations on Shor’s and Grover’s algorithms were found. The first truly new quantum algorithms were discovered starting in 2001. Now there are many quantum algorithms found using a variety of approaches, though the applications remain restricted.  My recent overview of quantum computing mentions many of these algorithms. Bacon and van Dam provide a more detailed, but still high level, view of these algorithms. They group the algorithms into four categories corresponding to different approaches: quantum random walks, wave packet scattering, finding hidden symmetries, and simulating quantum physics. I hope many of you will enjoy learning more about, in their words, “the benefits of … studying the notion of an algorithm through the perspective of the physical laws of the universe.”

Which 2009 research results excited you the most?

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Which research result excited you the most in the past year? We’re not asking for the one you thought most important, or the one that would be most exciting to everyone, but which one got you, personally, most excited.

I’ll start things off with a result that delighted me so much I went around smiling all day, only feeling sad that more people couldn’t appreciate it! The result, that appeared in two papers almost simultaneously, is that some quantum states are too entangled to be able to compute one way. The result enchants me because it is surprising, fundamental, and related to topics close to my heart. Prior to these papers, the conventional wisdom held that more entanglement could only help quantum computation. It came as a complete surprise that it could hurt!  Dave Bacon writes beautifully and succinctly about these startling results in his viewpoint, published in Physics, about the two papers published together in Physics Review Letters 102 last May. Here I give an briefer account in order to explain why these result delighted me so much.

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