Learning Disordered Topological Phases by Statistical Recovery of Symmetry
This work addresses the challenge of identifying topological phases in disordered quantum systems for physicists, though it is incremental as it applies existing neural network methods to a new context.
The researchers tackled the problem of mapping the quantum phase diagram of a disordered topological superconductor using an artificial neural network, achieving high-confidence classification of phases like the thermal metal phase, with results consistent with traditional methods such as transfer matrix calculations.
In this letter, we apply the artificial neural network in a supervised manner to map out the quantum phase diagram of disordered topological superconductor in class DIII. Given the disorder that keeps the discrete symmetries of the ensemble as a whole, translational symmetry which is broken in the quasiparticle distribution individually is recovered statistically by taking an ensemble average. By using this, we classify the phases by the artificial neural network that learned the quasiparticle distribution in the clean limit, and show that the result is totally consistent with the calculation by the transfer matrix method or noncommutative geometry approach. If all three phases, namely the $\mathbb{Z}_2$, trivial, and the thermal metal phases appear in the clean limit, the machine can classify them with high confidence over the entire phase diagram. If only the former two phases are present, we find that the machine remains confused in the certain region, leading us to conclude the detection of the unknown phase which is eventually identified as the thermal metal phase. In our method, only the first moment of the quasiparticle distribution is used for input, but application to a wider variety of systems is expected by the inclusion of higher moments.