Philip Ball — Quantum Theory Rebuilt From Simple Physical Principles

Important from the perspective of philosophy of science.

Perhaps the most significant line is the last one:

What is needed is new mathematics that will render these notions scientific,” he said. Then, perhaps, we’ll understand what we’ve been arguing about for so long.

Recall that Newton had to develop the calculus as a new mathematical notation in order to express his discoveries in classical physics.

Quanta Magazine
Quantum Theory Rebuilt From Simple Physical Principles

Philip Ball

Steven Weinberg — The Trouble with Quantum Mechanics

Determinism and probability in physics.

Probability was not unfamiliar to the physicists of the 1920s, but it had generally been thought to reflect an imperfect knowledge of whatever was under study, not an indeterminism in the underlying physical laws. Newton’s theories of motion and gravitation had set the standard of deterministic laws. When we have reasonably precise knowledge of the location and velocity of each body in the solar system at a given moment, Newton’s laws tell us with good accuracy where they will all be for a long time in the future. 

Probability enters Newtonian physics only when our knowledge is imperfect, as for example when we do not have precise knowledge of how a pair of dice is thrown. But with the new quantum mechanics, the moment-to-moment determinism of the laws of physics themselves seemed to be lost.... 

In quantum mechanics the state of a system is not described by giving the position and velocity of every particle and the values and rates of change of various fields, as in classical physics. Instead, the state of any system at any moment is described by a wave function, essentially a list of numbers, one number for every possible configuration of the system.6 If the system is a single particle, then there is a number for every possible position in space that the particle may occupy. This is something like the description of a sound wave in classical physics, except that for a sound wave a number for each position in space gives the pressure of the air at that point, while for a particle in quantum mechanics the wave function’s number for a given position reflects the probability that the particle is at that position. What is so terrible about that? ... 

Even so, I’m not as sure as I once was about the future of quantum mechanics. It is a bad sign that those physicists today who are most comfortable with quantum mechanics do not agree with one another about what it all means. The dispute arises chiefly regarding the nature of measurement in quantum mechanics.… 

The introduction of probability into the principles of physics was disturbing to past physicists, but the trouble with quantum mechanics is not that it involves probabilities. We can live with that. The trouble is that in quantum mechanics the way that wave functions change with time is governed by an equation, the Schrödinger equation, that does not involve probabilities. It is just as deterministic as Newton’s equations of motion and gravitation. That is, given the wave function at any moment, the Schrödinger equation will tell you precisely what the wave function will be at any future time. There is not even the possibility of chaos, the extreme sensitivity to initial conditions that is possible in Newtonian mechanics. So if we regard the whole process of measurement as being governed by the equations of quantum mechanics, and these equations are perfectly deterministic, how do probabilities get into quantum mechanics?… 

Today there are two widely followed approaches to quantum mechanics, the “realist” and “instrumentalist” approaches, which view the origin of probability in measurement in two very different ways. For reasons I will explain, neither approach seems to me quite satisfactory.…

The New York Review of Books
The Trouble with Quantum Mechanics
Steven Weinberg | Jack S. Josey-Welch Foundation Chair in Science and Regental Professor; Director, Theory Research Group,, University of Texas, and Nobel Prize (Physics) recipient, 1979

Ohio State University — You're not irrational, you're just quantum probabilistic

Researchers explain human decision-making with physics theory…

"Whenever something comes up that isn't consistent with classical theories, we often label it as 'irrational.' But from the perspective of quantum cognition, some findings aren't irrational anymore. They're consistent with quantum theory--and with how people really behave."

In two new review papers in academic journals, Wang and her colleagues spell out their new theoretical approach to psychology. One paper appears in Current Directions in Psychological Science, and the other in Trends in Cognitive Sciences.

Their work suggests that thinking in a quantum-like way¬--essentially not following a conventional approach based on classical probability theory--enables humans to make important decisions in the face of uncertainty, and lets us confront complex questions despite our limited mental resources.

What was that about rational choice again?

Eureka Alert
You're not irrational, you're just quantum probabilistic
Ohio State University

ht Mark Thoma at Economist's View

MIT Technology Review — Poll Reveals Quantum Physicists’ Disagreement About the Nature of Reality

A survey of leading thinkers shows that they are as far as ever from agreeing on the nature of reality

MIT Technology Review | The Physics arXiv Blog
Poll Reveals Quantum Physicists’ Disagreement About the Nature of Reality

Here is the study.