Quantum Mechanics: Can We Invalidate It with an Experiment?

Over the years, quantum mechanics (QM) has overwhelmingly passed every test it has been subjected to. However, the theory remains deeply counterintuitive and tails away into the abstract. This has led many to question whether a single experiment could potentially invalidate QM.

Current State and Verifications of Quantum Mechanics

QM has been thoroughly verified and passed all tests it has encountered. It is widely accepted and relied upon in numerous scientific fields. The fact that Newtonian mechanics fails in certain domains is unsurprising, but the vast range over which it remains applicable is astounding. Despite these successes, the interpretation of QM remains contested, particularly concerning wave/particle duality.

Challenging Quantum Mechanics with Thought Experiments

While there is no experiment that could definitively invalidate QM, several thought and real experiments challenge our classical perceptions of quantum mechanics. These experiments underscore the counterintuitive nature of quantum phenomena. One of the most famous thought experiments involves the double-slit experiment, which demonstrates wave-particle duality and non-locality.

Wave/Particle Duality: A Critical Experiment

One critical experiment that could definitively settle the question of wave/particle duality involves the use of a beam splitter and two photon detectors. The idea is to shoot photons at the beam splitter one by one and observe the detectors. According to classical wave theory, if both detectors were to register clicks, the system would collapse into a wave-like state. However, in reality, only one detector clicks each time, which aligns with the particle-like behavior of photons.

While this thought experiment poses a clear challenge to the wave theory of light, the practical limitations of current technology make it impossible to perform. For instance, we lack a "photon pea-shooter" and the technology to observe photons individually with the necessary precision. Despite this, the assumption that this experiment has been done underpins many of the so-called 'mind-bending' paradoxes in quantum mechanics.

Theoretical Interpretations of Quantum Mechanics

There is no consensus among physicists about the correct interpretation of QM. Several interpretations exist, each with its own merits and challenges. The many-worlds interpretation, for example, proposes that every quantum measurement results in a new universe where there is a different outcome. This interpretation is often considered a realist view, as it maintains a certain continuity with classical reality.

Bohmian mechanics, on the other hand, introduces a deterministic framework where particles have definite positions, and the wavefunction guides their motion. While it maintains the wavefunction, it does not conform to the idea of wave/particle duality as strictly as the many-worlds interpretation. It has been proposed as a way to incorporate particle creation and annihilation into the theory, although consensus on its implementation remains elusive.

Potential Refutation of Realism

Somewhat controversially, there are some references to the idea of an experiment that could refute realism in QM. However, it is often argued that such a claim is premature. The assumption that QM will one day be falsified, while potentially true, is not supported by current experimental results. As long as all known results align with QM, it is unlikely that a single experiment would significantly shift the interpretation towards anti-realism.

While some may favor anti-realism on philosophical grounds, the overwhelming body of evidence supports realist interpretations of QM. The experimental results consistently align with QM, and the many-worlds and Bohmian interpretations offer plausible pathways to understanding quantum phenomena without resorting to radical non-intuitive ideas.