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arXiv · 2505.01920

Interference in complex canonical variables is not quantum

Chiara Marletto·Vlatko Vedral
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Abstract

We formally represent the quantum interference of a single qubit embodied by a photon in the Mach-Zehnder interferometer using the classical Hamiltonian framework but with complex canonical variables. Although all operations on a single qubit can be formally expressed using the complex classical Hamiltonian dynamics, we show that the resulting system is still not a proper qubit. The reason is that it is not capable of getting entangled to another bona fide qubit and hence it does not have the information-processing capacity of a fully-fledged quantum system. This simple example powerfully illustrates the failure of all hybrid quantum-classical models in accounting for the full range of behaviour of even a single quantum bit.

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Chiara Marletto, Vlatko Vedral. 2025-05-03. Interference in complex canonical variables is not quantum. https://arxiv.org/abs/2505.01920

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