QBism, the Perimeter of Quantum Bayesianism

TL;DR

QBism interprets quantum mechanics through a Bayesian lens, emphasizing probabilities, information theory, and the concept of dimension, aiming to represent quantum phenomena without traditional wavefunctions or operators.

Contribution

This paper introduces a probabilistic formulation of quantum mechanics based on QBism, highlighting the role of symmetric informationally complete measurements and the concept of dimension as a universal capacity.

Findings

Quantum states are represented as personalist Bayesian probabilities.

The Born Rule is viewed as an extension of probability theory.

Symmetric informationally complete measurements are central to the new representation.

Abstract

This article summarizes the Quantum Bayesian point of view of quantum mechanics, with special emphasis on the view's outer edges---dubbed QBism. QBism has its roots in personalist Bayesian probability theory, is crucially dependent upon the tools of quantum information theory, and most recently, has set out to investigate whether the physical world might be of a type sketched by some false-started philosophies of 100 years ago (pragmatism, pluralism, nonreductionism, and meliorism). Beyond conceptual issues, work at Perimeter Institute is focused on the hard technical problem of finding a good representation of quantum mechanics purely in terms of probabilities, without amplitudes or Hilbert-space operators. The best candidate representation involves a mysterious entity called a symmetric informationally complete quantum measurement. Contemplation of it gives a way of thinking of the Born Rule as an addition to the rules of probability theory, applicable when an agent considers gambling on the consequences of his interactions with a newly recognized universal capacity: dimension (formerly Hilbert-space dimension). (The word "capacity" should conjure up an image of something like gravitational mass---a body's mass measures its capacity to attract other bodies. With hindsight one can say that the founders of quantum mechanics discovered another universal capacity, "dimension.") The article ends by showing that the egocentric elements in QBism represent no impediment to pursuing quantum cosmology and outlining some directions for future work.