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Variational consistent histories as a hybrid algorithm for quantum foundations

Nature communications 10(1)
Arrasmith, A.Cincio, L.Sornborger, A.T.Zurek, W.H.Coles, P.J. Theoretical Division,
MS, Los Alamos National Laboratory,

Department of Physics,
University of California Davis,

Information Sciences,
MS, Los Alamos National Laboratory,
2019 Physics

While quantum computers are predicted to have many commercial applications, less attention has been given to their potential for resolving foundational issues in quantum mechanics. Here we focus on quantum computers’ utility for the Consistent Histories formalism, which has previously been employed to study quantum cosmology, quantum paradoxes, and the quantum-to-classical transition. We present a variational hybrid quantum-classical algorithm for finding consistent histories, which should revitalize interest in this formalism by allowing classically impossible calculations to be performed.


In our algorithm, the quantum computer evaluates the decoherence functional (with exponential speedup in both the number of qubits and the number of times in the history), and a classical optimizer adjusts the history parameters to improve consistency. We implement our algorithm on a cloud quantum computer to find consistent histories for a spin in a magnetic field, and on a simulator to observe the emergence of classicality for a chiral molecule.

The article was published in: Nature communications 10(1): 3438.

Full article

This work was supported (in part) by the Fetzer Franklin Fund of the John E. Fetzer Memorial Trust.