An interpretation of quantum mechanics dating back to mid-1950s, based on the ideas of Hugh Everett III, has found a new lease on life in recent decades. Significant efforts have been made by physicists and philosophers of physics to bring advances in physics and philosophy to bear on the interpretation, and to overcome some of the shortcomings in Everett's bold, but limited writings. This article presents an introduction to Everettian quantum mechanics.
An interpretation of quantum mechanics dating back to mid-1950s, based on the ideas of Hugh Everett III, has found a new lease on life in recent decades. Significant efforts have been made by physicists and philosophers of physics to bring advances in physics and philosophy to bear on the interpretation, and to overcome some of the shortcomings in Everett's bold, but limited writings. This article presents an introduction to Everettian quantum mechanics.
This book presents the most comprehensive study yet of a problem that has puzzled physicists and philosophers since the 1930s. The standard theory of quantum mechanics is in one sense the most successful physical theory ever, predicting the behaviour of the basic constituents of all physical things; no other theory has ever made such accurate empirical predictions. However, if one tries to understand the theory as providing a complete and accurate framework for the description of the behaviour of all physical interactions, it becomes evident that the theory is ambiguous, or even logically inconsistent. The most notable attempt to formulate the theory so as to deal with this problem, the quantum measurement problem, was initiated by Hugh Everett III in the 1950s. This book gives a careful and challenging examination and evaluation of the work of Everett and those who have followed him. The informal approach, minimizing technicality, makes the book accessible and illuminating for philosophers and physicists alike.
Introduction In the July 1957 issue of the Reviews of Modern Physics: Hugh Everett iii put forward a new interpretation of quantum mechanics (Everett 1957). John Wheeler, Everett's thesis adviser, published, in the same issue, an accompanying paper supporting Everett's views (Wheeler 1957). Everett's aim was to cut through the fuzzy thinking displayed by many authors, some of them quite prominent, who in previous years had written incredibly dull papers on how they understood quantum mechanics. Everett's idea was simply to assume that quantum mechanics provides a description of reality in exactly the same sense as classical mechanics was once thought to do. This is a shocking idea, for it leads to a multiplicity of “realities.” Few physicists in 1957 were prepared to accept it. And yet it can be shown to work. It is the purpose of this article to expand on Everett's original demonstration and to reveal the courage John Wheeler displayed in betting that his student was right. Classical theory of measurement System, apparatus, coupling Our starting point is the standard theory of measurement, which we shall first examine classically. In its simplest form a measurement involves just two dynamical entities: a system and an apparatus . It is the role of the apparatus to record the value of some system observable s . For this purpose system and apparatus must be coupled together for a certain period of time, which will be taken to be finite.
Abstract This book presents the most comprehensive study yet of a problem that has puzzled physicists and philosophers since the 1930s. The standard theory of quantum mechanics is in one sense the most successful physical theory ever, predicting the behaviour of the basic constituents of all physical things; no other theory has ever made such accurate empirical predictions. However, if one tries to understand the theory as providing a complete and accurate framework for the description of the behaviour of all physical interactions, it becomes evident that the theory is ambiguous, or even logically inconsistent. The most notable attempt to formulate the theory so as to deal with this problem, the quantum measurement problem, was initiated by Hugh Everett III in the 1950s. This book gives a careful and challenging examination and evaluation of the work of Everett and those who have followed him. The informal approach, minimizing technicality, makes the book accessible and illuminating for philosophers and physicists alike.
The Everett interpretation of quantum mechanics - better known as the Many-Worlds Theory - has had a rather uneven reception. Mainstream philosophers have scarcely heard of it, save as science fiction. In philosophy of physics it is well known but has historically been fairly widely rejected. Among physicists (at least, among those concerned with the interpretation of quantum mechanics in the first place), it is taken very seriously indeed, arguably tied for first place in popularity with more traditional operationalist views of quantum mechanics. In this article, I provide a fairly short (15,000 words) and self-contained introduction to the Everett interpretation as it is currently understood. I use little technical machinery, although I do assume the reader has encountered the measurement problem already (at about the level of the well-known discussions by Penrose or Albert).
It has been 61 years since Hugh Everett III's PhD dissertation, {\it On the Foundations of Quantum Mechanics}, was submitted to the Princeton University Physics Department. After more than a decade of relative obscurity it was resurrected by Bryce DeWitt as {\it The Many Worlds Interpretation of Quantum Mechanics} and since then has become an active topic of discussion, reinterpretation, and modification, especially among philosophers of science, quantum cosmologists, and advocates of quantum decoherence and quantum computing. Many of these analyses are quite sophisticated and considered to be important contributions to physics and philosophy. I am primarily an experimental physicist and my pragmatic ruminations on the subject might viewed with some suspicion. Indeed, Bohr's pragmatic {\it Copenhagen Interpretation} is often disparaged by this same cohort. Still, I think that my experimentalist's vantage point has something to offer and I here offer it to you.
abstract: This thesis attempts to explain Everettian quantum mechanics from the ground up, such that those with little to no experience in quantum physics can understand it. First, we introduce the history of quantum theory, and some concepts that make up the framework of quantum physics. Through these concepts, we reveal why interpretations are necessary to map the quantum world onto our classical world. We then introduce the Copenhagen interpretation, and how many-worlds differs from it. From there, we dive into the concepts of entanglement and decoherence, explaining how worlds branch in an Everettian universe, and how an Everettian universe can appear as our classical observed world. From there, we attempt to answer common questions about many-worlds and discuss whether there are philosophical ramifications to believing such a theory. Finally, we look at whether the many-worlds interpretation can be proven, and why one might choose to believe it. (abstract)