You can pin down one or the other but not both.

## Quantum Physics

The measurement problem. Most of quantum mechanics deals with probabilities rather than certainties. A particle has a probability of appearing in a certain place. An unstable atom has a probability of decaying at a certain instant.

- Privacy Technologies and Policy: Second Annual Privacy Forum, APF 2014, Athens, Greece, May 20-21, 2014. Proceedings!
- Quanta Magazine!
- Quantum Mechanics at the Crossroads.
- The Utopian Vision of Charles Fourier: Selected Texts on Work, Love, and Passionate Attraction!

But when a physicist goes into the laboratory and performs an experiment, there is a definite outcome. The act of measurement — observation, by someone or something — becomes an inextricable part of the theory.

## What Does Quantum Theory Actually Tell Us about Reality?

The strange implication is that the reality of the quantum world remains amorphous or indefinite until scientists start measuring. This is disturbing to philosophers as well as physicists.

So quantum physics — quite unlike any other realm of science — has acquired its own metaphysics, a shadow discipline tagging along like the tail of a comet. This field is called quantum foundations, which is inadvertently ironic, because the point is that precisely where you would expect foundations you instead find quicksand.

The first and still possibly foremost of these is the so-called Copenhagen interpretation. In a way, the Copenhagen is an anti-interpretation.

Physics can help us order experience but should not be expected to provide a complete picture of reality. For much of the 20th century, when quantum physicists were making giant leaps in solid-state and high-energy physics, few of them bothered much about foundations.

## A realist takes on quantum mechanics

But the philosophical difficulties were always there, troubling those who cared to worry about them. It goes from being spread out before measurement to peaking at one of those places where the photon materializes upon measurement. This apparent measurement-induced collapse of the wave function is the source of many conceptual difficulties in quantum mechanics.

The photon is not real in the sense that a plane flying from San Francisco to New York is real.

In the double-slit experiment done with single photons, all one can do is verify the probabilistic predictions of the mathematics. Also, there are other ways of interpreting the double-slit experiment. A photon heads towards the double slit with a definite position at all times and goes through one slit or the other; so each photon has a trajectory.

The controversy notwithstanding, the experiments show that the de Broglie-Bohm theory remains in the running as an explanation for the behavior of the quantum world.

### Aeon for Friends

Crucially, the theory does not need observers or measurements or a non-material consciousness. Observers merely discover the outcome. Collapse theories predict that when particles of matter become more massive than some threshold, they cannot remain in a quantum superposition of going through both slits at once, and this will destroy the interference pattern.

The search for the threshold continues. No consciousness needed. Conceptually, the idea is to not just put a photon into a superposition of going through two slits at once, but to also put one of the slits in a superposition of being in two locations at once. FAQ Policy. About this book It may tum out that, like certain other phenomena studied by sociologists, bouts of interest in the foundations of quantum mechanics tend to come in year cycles. Show all. Quantum Nonlocality Pages Home, Dipankar. Show next xx. Read this book on SpringerLink. Services for this Book Download Product Flyer.