Security Evaluation of Quantum Circuit Split Compilation under an Oracle-Guided Attack

Quantum circuits are the fundamental representation of quantum algorithms and constitute valuable intellectual property (IP). Multiple quantum circuit obfuscation (QCO) techniques have been proposed in prior research to protect quantum circuit IP against malicious compilers. However, there has not been a thorough security evaluation of these schemes. In this work, we investigate the resilience of split compilation against an oracle-guided attack. Split compilation is one of the most studied QCO techniques, where the circuit to be compiled is split into two disjoint partitions. Each split circuit is known to the compiler, but the interconnections between them are hidden. We propose an oracle-guided security evaluation framework in which candidate connections are systematically tested against input-output observations, with iteratively pruned inconsistent mappings. This hierarchical matching process exploits the reversibility of quantum gates and reduces the search space compared to brute-force enumeration. Experimental evaluation in the RevLib benchmark suite shows that only a small number of I/O pairs are sufficient to recover the correct inter-split connections and reconstruct the entire circuits. Our study marks the first thorough security evaluations in quantum IP protection and highlights the necessity of such evaluations in the development of new protection schemes.