TY - JOUR

T1 - Emergence of Classical Magnetic Order from Anderson Towers: Quantum Darwinism in Action

AU - Sotnikov, O.

AU - Stepanov, E.

AU - Katsnelson, M.

AU - Mila, F.

AU - Mazurenko, V. 

N1 - We thank Andrey Bagrov and Tom Westerhout for useful discussions. We also thank an anonymous referee for very insightful comments on the connection between our results and the standard theory of pointer states. This work was supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under Research Preparation Grants with Russia 2020, the project Quantum skyrmions. V. V. M. and O. M. S. also acknowledge the support from the Russian Roadmap on Quantum Computing (Contract No. 868-1.3-15/15-2021). The work of M. I. K. was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program, Grant Agreement No. 854843-FASTCORR. The work of E. A. S. was supported by the European Union’s Horizon 2020 Research and Innovation program under the Marie Skłodowska Curie Grant Agreement No. 839551-2DMAGICS. Exact diagonalization calculations were performed on the Uran supercomputer at the IMM UB RAS.

PY - 2023

Y1 - 2023

N2 - Environment is assumed to play a negative role in quantum mechanics, destroying the coherence in a quantum system and, thus, randomly changing its state. However, for a quantum system that is initially in a degenerate ground state, the situation could be different. In this case, the infinite manifold of ground state eigenfunctions can contain a few states of zero entanglement, which can be demonstrated based on the minimization of the von Neumann entropy. Then, following quantum Darwinism, these “classical” combinations are selected and promoted by the quantum environment, which means that different independent observers find them in experiments. In this work, we find and explore such classical states in the eigenspectra of skyrmionic and antiferromagnetic quantum systems starting from a numerical realization of Anderson’s tower of states. The degeneracy of the quantum ground state is shown to be the key for explaining nontrivial properties of magnetic matter in the classical world including topological protection arising in the classical limit.

AB - Environment is assumed to play a negative role in quantum mechanics, destroying the coherence in a quantum system and, thus, randomly changing its state. However, for a quantum system that is initially in a degenerate ground state, the situation could be different. In this case, the infinite manifold of ground state eigenfunctions can contain a few states of zero entanglement, which can be demonstrated based on the minimization of the von Neumann entropy. Then, following quantum Darwinism, these “classical” combinations are selected and promoted by the quantum environment, which means that different independent observers find them in experiments. In this work, we find and explore such classical states in the eigenspectra of skyrmionic and antiferromagnetic quantum systems starting from a numerical realization of Anderson’s tower of states. The degeneracy of the quantum ground state is shown to be the key for explaining nontrivial properties of magnetic matter in the classical world including topological protection arising in the classical limit.

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U2 - 10.1103/PhysRevX.13.041027

DO - 10.1103/PhysRevX.13.041027

M3 - Article

VL - 13

JO - Physical Review X

JF - Physical Review X

SN - 2160-3308

IS - 4

M1 - 041027

ER -