I was sorry to learn today of the death on April 15th of H. Dieter Zeh, one of the major figures responsible for improving our understanding of the physics involved in the measurement problem and related interpretational issues in quantum mechanics. For an excellent account of the story of Zeh’s work and its early reception, see Adam Becker’s recent book What is Real?. For a very good article about Zeh (in German), see here.
Zeh is the physicist most responsible for first identifying and studying the crucial role of decoherence in the measurement problem. As Becker explains, he encountered a quite hostile reaction to his early work from defenders of Copenhagen orthodoxy. He finally managed to get his paper On the Interpretation of Measurement in Quantum Theory published in 1970, and then started to explore what came to be known later by the term “decoherence”. In later years he wrote many articles explaining these ideas, for one that includes some historical context, see here. Zeh maintained a website with links to his writings, at www.decoherence.de or www.zeh-hd.de, which seems to be down at the moment, hopefully only a temporary situation (a recent Wayback Machine capture is here).
I was pleased that every so often Zeh contributed insightful comments here, most recently just three weeks before his death. Here’s a list of the ones I found in a quick search:
During the past few years I also had some email exchanges with Zeh. For details of his latest thinking about issues like the multiverse, he pointed me to this paper, which he every so often updated. A few months ago I was quite sorry to realize (when someone told me that Zeh lived in Heidelberg) that I had missed an opportunity to try to meet him in person when I was there a couple years ago. I’m even sorrier about this now that such a meeting will no longer be possible.