Quantum Bayesianism; Putting the Scientist Back in Science
Considering the ongoing challenge of taking measurements in the quantum world and the meaning and accuracy of those measurements, do they form a true picture? Some say not. Objectivity and subjectivity come into the equation. Not to be left out is the philosophical view. Qubit.
Excerpts and salient points ~
• Bayesianism is widely used in areas such as decision theory, behavioural economics, and artificial intelligence. When applied to quantum mechanics in QBism, it says, for example, that the probability of a measurement on a quantum system giving a certain result does not give us real information about the actual world. The probability is merely a guide to making the best decision about where, say, to find a particle.
• One enthusiast is the US physicist David Mermin. In a 2013 interview, he said that probabilities in QBism “have a strategic aspect”. And since “strategy implies a strategist,” he continued, “in that sense quantum probabilities are subjective”. Measurements do not affect nature, but guide the measuring subjects in what to believe.
• Quantum Bayesianism is thus a radical attempt to resolve quantum puzzles by treating its probabilities not as features of objective reality, but of subjective belief. It’s a participatory approach to physics. As Mermin declared in 2014 in Nature (507 421): “QBism put the scientist back into science.”
• By regarding the wave function as less a real thing than an embodiment of available information, QBism eliminates a host of puzzles and paradoxes. The perplexing “reduction” of the wave function, for instance, is nothing more than an updating of information, a new quantitative guide to what it is possible to believe. The paradox of Wigner’s friend is resolved because Wigner and the friend have different information. As for Schrödinger’s cat, it is rescued from existential blurring because the wave equation only encodes what we non-cats currently know.
• Philosophy, as I’ve said many times, can often be spotted in physics wherever an issue arises that can’t be resolved by more research. QBism is one such case. Though seemingly able to resolve puzzles in a straightforward way, it makes certain specific assumptions about the nature of reality – assumptions that philosophy can help to clarify and analyse.
Content may have been edited for style and clarity.
