Zureka: a way forward to solving the thorniest issues in quantum mechanics

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Zureka: a way forward to solving the thorniest issues in quantum mechanics<br>Issues of interpretation have haunted quantum mechanics for a century. I think the most promising way out is actually a "conservative upgrade" to the orthodox framework we already use.

Deivon Drago<br>Jul 11, 2026

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Caveat lector: this essay is a little technical and assumes that you have at least a passing familiarity with the basic concepts and issues in quantum mechanics.<br>Background

Most physicists aren’t all that keen on debating philosophical issues related to quantum foundations, i.e., clarifying what certain concepts in quantum mechanics (QM) actually mean.<br>Thanks for reading! Subscribe for free to receive new posts and support my work.

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(Some physics departments actually go so far as to discourage papers and grant proposals focused on quantum foundations.)<br>There are also physicists who deny that a problem really exists. But what the “shut up and calculate” crowd, as this group is often referred to, needs to come to terms with is - at the heart of QM, a key pillar of modern physics, are some thorny unresolved theoretical issues.<br>For example, let’s look at how quantum systems evolve in the textbook formulation of QM (often called the “Copenhagen” interpretation.) There are two incompatible rules as to how the dynamics of a quantum system evolve over time.<br>Rule one is embodied by the Schrödinger equation. The rule is essentially smooth, deterministic, and reversible. We hand it a quantum state, and it’ll tell us exactly what that state becomes at every future moment. This rule is, as far as we can tell, “exactly true”. We have successfully tested it to great precision.<br>Rule two is the measurement postulate, or as some refer to it, the so-called “collapse” postulate. When you measure a quantum system, its smoothly evolving superposition (see Rule one) abruptly jumps to a “definite outcome”, with probabilities given by the Born rule. (Explainer: each possible outcome carries a number called its “amplitude.” If we square that number, we get the probability of actually seeing that outcome. That squaring is the Born rule.) This rule is also, as far as we can tell, exactly true. Every experiment confirms it.<br>The trouble is - these two rules cannot “both” be fundamental. The first says superpositions never collapse. The second says they do, precisely when we “look”. Worse, rule two quietly smuggles in undefined words. What counts as a “measurement”? What counts as an “observer”? A Geiger counter? A cat? A grad student? The math of textbook quantum mechanics genuinely “does not say”. It just tells you to draw a line somewhere between the quantum system and the classical apparatus, perform the collapse there, and not ask too many questions.<br>This is the “measurement problem”, and it has been sitting at the foundations of QM for roughly a century. If you look closer, it actually breaks down into a few distinct puzzles that people tend to mash together:<br>The preferred basis problem. A “basis” is just the set of distinct alternatives you choose to describe a state in terms of “alive-or-dead”, say, or even using some bizarre “alive-plus-dead” and “alive-minus-dead” options. The unsettling part is that the math treats all these choices as “equally valid”. That is, a single superposition can be written infinitely many ways depending on “which basis you pick”. So “when we look”, why do we always see the “familiar” alternatives - definite “positions” - rather than the weird combinations (e.g., here-and-there, alive-plus-dead, etc.)? What “singles out” the classical-looking description?

The definite outcomes problem. Why do we observe “one” result rather than a smeared-out superposition of all of them?<br>Think of this problem as following on from the preferred basis one. Choosing a basis is like choosing a tree from the forest. Choosing a single outcome is like choosing a branch of that tree. Even if you solve the preferred basis problem re tree selection, you still have the definite outcomes selection re branch selection.<br>Also, please note that I’m speaking figuratively. No one is doing any “actual choosing”. Nothing in the unitary dynamics does any selecting at all. Rather, we might say the branches all coexist and the question is why we find ourselves on one specific one.

The probabilities problem. Where does the Born rule come from? Why does squaring the amplitude to get the probability work, and not some other recipe?

The objectivity problem. This one is (sort of) underrated and often not listed as a problem. Why do “different observers always agree” on the outcome? You and I can both check whether the cat is alive without destroying the result, but we always concur (meaning the cat is either alive or dead for both of us). In quantum mechanics, measurement generally disturbs the thing that is measured, so this “universal...