Feynman:”It is safe to say that no one understands Quantum Mechanics.”
Einstein: “Insanity is doing the same thing over and over and expecting different results.”
Nature: “That’s how the world works.”
Wilzcek (Physics Nobel Prize): “Naïveté is doing the same thing over and over, and always expecting the same result.”
Parmenides, the ancient Greek philosopher, theorized that reality is unchanging and indivisible and that movement is an illusion. Zeno, a student of Parmenides, devised four famous paradoxes to illustrate the logical difficulties in the very concept of motion. Zeno’s arrow paradox starts and ends this way:
- If you know where an arrow is, you know everything about its physical state….
- The arrow does not move…
Classical Mechanics found the first point to be erroneous. To know the state of a particle, one must know not only its position X, but also its velocity and mass (what’s called its momentum P). Something similar happens with Quantum Physics. To know the state of a particle, we need to know whether the state of what it has interacted with before… exists, or not. According to old fashion metaphysics, that’s beyond weird. It’s simply incomprehensible.
[The Nazi philosopher Heidegger, an ex would-be priest, wrote a famous book “Being And Time“. However, rather than a fascist fantasy, the EPR is exactly about that level of depth: how existence and time come to be! And how those interact with our will…]
With that information, X and P, position and momentum, for each particle, classical mechanics predicts a set of particles’ future evolution completely. (Formally dynamic evolution satisfies a second order linear differential equation. That was thoroughly checked by thousands of officers of gunnery, worldwide, over the last five centuries.)
Highly predicting classical mechanics is the model of Einstein Sanity.
Aristotle had ignored the notion of momentum, P. For Aristotle, one needed a force to maintain motion (an objective proof of Aristotle’s stupidity; no wonder Aristotle supported, and instigated, fascist dictatorship as the best system of governance). Around 1320 CE, the Parisian genius Buridan declared that Aristotle was completely wrong and introduced momentum P, calling it “IMPETUS”.
May we be in a similar situation? Just like the Ancient Greeks had ignored P, is Quantum Wave Mechanics incomplete from an inadequate concept of what a complete description of the world is?
Einstein thought so, and demonstrated it to his satisfaction in his EPR Thought Experiment. The EPR paper basically observed that, according to the Quantum Axiomatics, two particles, after they interacted still formed JUST ONE WAVE. Einstein claimed that there had to exist hidden “elements of reality”, not yet identified in the (Copenhagen Interpretation of) quantum theory. Those heretofore hidden “elements of reality” would re-establish Einstein Sanity, Einstein feverishly hoped.
According to Einstein, following his friend Prince Louis De Broglie (to whom he had conferred the Doctorate) and maybe the philosopher Karl Popper (with whom he corresponded prior on non-locality), Quantum Mechanics appears random. But that randomness is only because of our ignorance of those “hidden variables.” Einstein’s demonstration rested on the impossibility of what he labelled “spooky action at a distance”.
That was an idea too far. The “spooky action at a distance” has been (amply) demonstrated in the meantime. Decades of experimental tests, including a “loophole-free” test published on the scientific preprint site arxiv.org last month, show that the world is like that: completely non-local everywhere.
In 1964, the physicist John Bell, CERN’s theory chief, working with David Bohm’s version of Einstein’s EPR thought experiment, identified an inequality obeyed by any physical theory that is both local — meaning that interactions don’t travel faster than light — and where the physical properties usually attributed to “particles” exist prior to “measurement.”
(As an interesting aside, Richard Feynman tried to steal Bell’s result, at a time when Bell was not famous, at least in the USA: a nice example of “French Theory” at work! And I love Feynman…)
Einstein’s hidden “elements of reality” probably exist, but they are NON-LOCAL. (Einstein was obsessed by locality; but that’s an error. All what can be said in favor of locality is that mathematics, and Field Theory, so far, are local: that’s the famous story of the drunk who looks for his keys under the lamp post, because that’s the only thing he sees.)
Either some physical influences travel faster than light, or some properties don’t exist before measurement. Or both
I believe both happen. Yes, both: reality is both faster than light, and it is pointwise fabricated by interactions (“measurement”). Because:
- The EPR Thought Experiment established the faster than light influence (and that was checked experimentally).
- But then some properties cannot exist prior to “EPR style influence”. Because, if they did, why do they have no influence whatsoever, once the EPR effect is launched?
Now visualize the “isolated” “particle”. It’s neither truly “isolated” nor truly a “particle”, as some of its properties have not come in existence yet. How to achieve this lack of existence elegantly? Through non-localization, as observed in the one-slit and two-slit experiments.
Why did I say that the “isolated” “particle” was not isolated? Because it interfered with some other “particle” before. Of course. Thus it’s EPR entangled with that prior “particle”. And when that “particle” is “measured” (namely INTERACTS with another “particle”), the so-called “isolated” “particle” gets changed, by the “spooky action at a distance”, at a speed much faster than light.
(This is no flight of fancy of mine, consecutive to some naïve misinterpretation; Zeilinger and Al. in Austria, back-checked the effect experimentally; Aspect in Paris and Zeilinger got the Wolf prize for their work on non-locality, so the appreciation for their art is not restricted to me!)
All these questions are extremely practical: they are at the heart of the difficulties in engineering a Quantum Computer.
Old physics is out of the window. The Quantum Computer is not here yet, because the new physics is not understood enough, yet.