A century after the Solvay Congress, de Broglie's pilot wave theory resurfaces as a deterministic alternative to quantum mechanics' randomness.
Historical meeting shaped quantum mechanics
Almost a century ago, at the fifth Solvay Congress in Brussels, modern quantum mechanics was born. Two worldviews clashed: on one side, the Copenhagen school, led by Niels Bohr, Werner Heisenberg, and Max Born, who argued that the world is intrinsically random and governed by probabilities, and on the other side, Albert Einstein, who defended classical determinism. A third path was proposed by Louis de Broglie, a French physicist, which was long discredited but has recently regained attention. Wave-particle duality introduced
De Broglie introduced the idea of associating a wave with each electron, leading to the concept of wave-particle duality. This idea was formalized in the Schrödinger equation in 1926. This duality is demonstrated in the two-slit experiment, where electrons, when sent one by one, create interference patterns on a screen, suggesting they behave as both particles and waves. Alternative to randomness proposed
To address this, de Broglie proposed the pilot wave theory, where particles are guided by a quantum wave, akin to a surfer on a wave. This theory was criticized by the Copenhagen school and later abandoned by de Broglie. It was rediscovered in 1952 by David Bohm and is now known as the Broglie-Bohm theory or dBB theory. This theory provides a deterministic framework, preserving particle trajectories and offering a resolution to quantum paradoxes like Schrödinger's cat. Recent challenge and response
Recently, the dBB theory faced challenges from an experiment conducted by Jan Klaers and his team, published in Nature. The experiment involved photons passing through a microbarrier, with the team claiming the dBB theory predicted zero velocity inside the barrier, which would contradict the observed results. However, further analysis by Aurélien Drezet and colleagues showed that the dBB theory actually aligns with the experimental results when considering the optical properties and energy flow. Ongoing debate and future research
The dBB theory remains a topic of debate, particularly in the realms of quantum field theory and quantum gravity, where extensions of the theory may be necessary. Despite these challenges, the theory's explanatory power based on clear trajectories offers a compelling alternative to the probabilistic interpretations of quantum mechanics.
