Tsim: Fast Universal Simulator for Quantum Error Correction

TL;DR

Tsim is an open-source, GPU-accelerated quantum circuit simulator that efficiently models quantum error correction using ZX diagrams, supporting universal noisy circuits with high throughput.

Contribution

It introduces Tsim, a novel simulator that combines ZX diagram representation, GPU acceleration, and Stim API compatibility for fast universal quantum error correction simulation.

Findings

Tsim achieves high throughput comparable to Stim for low-magic circuits.

It models Pauli channels as parameterized ZX vertices and simplifies diagrams via ZX rules.

Sampling time scales linearly with Clifford gates and exponentially with non-Clifford gates.

Abstract

We present Tsim, an open-source high-throughput simulator for universal noisy quantum circuits targeting quantum error correction. Tsim represents quantum circuits as ZX diagrams, where Pauli channels are modeled as parameterized vertices. Diagrams are simplified via parameterized ZX rules, and then compiled for vectorized sampling with GPU acceleration. After the one-time compilation, one can sample detector or measurement shots in linear time in the number of Clifford gates and exponentially only in the number of non-Clifford gates. Tsim implements the Stim API and fully supports the Stim circuit format, extending it with T and arbitrary single-qubit rotation instructions. For low-magic circuits, Tsim throughput can match the sampling performance of Stim.