Abstract

We consider two-dimensional lattice models that support Ising anyonic excitations and are coupled to a thermal bath. We propose a phenomenological model for the resulting short-time dynamics that includes pair-creation, hopping, braiding, and fusion of anyons. By explicitly constructing topological quantum error-correcting codes for this class of system, we use our thermalization model to estimate the lifetime of the quantum information stored in the encoded spaces. To decode and correct errors in these codes, we adapt several existing topological decoders to the non-Abelian setting. We perform large-scale numerical simulations of these two-dimensional Ising anyon systems and find that the thresholds of these models range between 13% to 25%. To our knowledge, these are the first numerical threshold estimates for quantum codes without explicit additive structure.

Highlights

  • One of the most interesting features of two-dimensional quantum systems with anyonic excitations [1] is their application to quantum information science, where the topological nature of the anyons offers some intrinsic protection of quantum coherence [2]

  • These topologically ordered systems are insensitive to local perturbations [3,4,5], have a ground-space degeneracy that is a function of the topology of the system [6,7], and can realize quantum gates by braiding anyons, which are naturally robust to error because of their topological nature [2,8]

  • We adapt two algorithms used in decoding Abelian anyon systems: a clustering renormalization group (RG) decoder introduced by Bravyi and Haah [34] and the perfect matching decoder [31]

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Summary

INTRODUCTION

One of the most interesting features of two-dimensional quantum systems with anyonic excitations [1] is their application to quantum information science, where the topological nature of the anyons offers some intrinsic protection of quantum coherence [2]. Non-Abelian anyon systems have excitations that can be used to implement topological quantum computation [10,11], and so they are of interest for quantum-information-processing schemes as well as quantum error correction. The local check operators can be measured using standard circuitry [32] on an ordinary, circuit-model quantum computer This second scenario we consider is not contingent on the existence of physical systems that naturally present topological quantum order; it could, in principle, be used in any quantum-computing architecture with nearest-neighbor interactions on a two-dimensional lattice. In this setting, our results provide an efficient decoding algorithm for the corresponding quantum error-correcting code. This provides the first efficient decoding schemes for a family of nonadditive quantum codes, i.e., codes without explicit Pauli-matrix tensor product structure

Summary of main results
PHENOMENOLOGICAL MODEL FOR ISING ANYON DYNAMICS
Fixed-rate sampling
Metropolis sampling
SIMULATING ISING ANYON PHENOMENOLOGY
Planar-graph simulations
Nonplanar graph simulations
QUANTUM ERROR-CORRECTING CODES IN ISING ANYON SYSTEMS
Ising fusion code
Ising topological code
Codes with boundaries
Determining code thresholds
DECODING ALGORITHMS
Simple clustering decoder
Fusion-aware clustering decoder
Perfect matching decoder
NUMERICAL RESULTS
Comparing code performance
Comparing decoder performance
Pair creation and decoherence
Pair creation dominated by hopping
Threshold analysis

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