QSpark: Towards Reliable Qiskit Code Generation

Abstract: Quantum circuits must be error-resilient, yet LLMs like Granite-20B-Code and StarCoder often output flawed Qiskit code. We fine-tuned a 32 B model with two RL methods, Group Relative Policy Optimization (GRPO) and Odds-Ratio Preference Optimization (ORPO), using a richly annotated synthetic dataset. On the Qiskit HumanEval benchmark, ORPO reaches 56.29\% Pass@1 ($\approx+10$ pp over Granite-8B-QK) and GRPO hits 49\%, both beating all general-purpose baselines; on the original HumanEval they score 65.90\% and 63.00\%. GRPO excels on basic tasks (42/54), ORPO on intermediate ones (41/68), and neither solves the five advanced tasks, highlighting clear gains yet room for progress in AI-assisted quantum programming.