Deterministic error model for quantum computer simulation

Quantum computers (QCs) must implement quantum error correcting codes (QECCs) to protect their logical qubits from errors, and modeling the effectiveness of QECCs on QCs is an important problem for evaluating the QC architecture. The previously developed Monte Carlo (MC) error models may take days or weeks of execution to produce an accurate result due to their random sampling approach. We present an alternative deterministic error model that generates, over the course of executing the quantum program, a probability tree of the QC's error states. By calculating the fidelity of the quantum program directly, this error model has the potential for enormous speedups over the MC model when applied to small yet useful problem sizes (containing on the order of a dozen logical qubits encoded in the [[7,1,3]] QECC plus associated ancilla). We observe a speedup on the order of 1000X when accuracy is required, and we evaluate the scaling properties of this new deterministic error model.