The success of quantum circuits in providing reliable outcomes for a given problem depends on the gate count and depth in near-term noisy quantum computers. Quantum circuit compilers that decompose high-level gates to native gates of the hardware and optimize the circuit play a key role in quantum computing. However, the quality and time complexity of the optimization process can vary significantly especially for practically relevant large-scale quantum circuits. As a result, third-party (often less-trusted/untrusted) compilers have emerged, claiming to provide better and faster optimization of complex quantum circuits than so-called trusted compilers. However, untrusted compilers can pose severe security risks, such as the theft of sensitive intellectual property (IP) embedded within the quantum circuit. We propose an obfuscation technique for quantum circuits using randomized reversible gates to protect them from such attacks during compilation. The idea is to insert a small random circuit into the original circuit and send it to the untrusted compiler. Since the circuit function is corrupted, the adversary may get incorrect IP. However, the user may also get incorrect output post-compilation. To circumvent this issue, we concatenate the inverse of the random circuit in the compiled circuit to recover the original functionality. We demonstrate the practicality of our method by conducting exhaustive experiments on a set of benchmark circuits and measuring the quality of obfuscation by calculating the Total Variation Distance (TVD) metric. Our method achieves TVD of up to 1.92 and performs at least 2X better than a previously reported obfuscation method. We also propose a novel adversarial reverse engineering (RE) approach and show that the proposed obfuscation is resilient against RE attacks. The proposed technique introduces minimal degradation in fidelity (~1% to ~3% on average).

翻译：在近期的含噪量子计算机中，量子电路能否为特定问题提供可靠结果取决于电路中的门数量和深度。将高级门分解为硬件原生门并优化电路的量子电路编译器在量子计算中扮演关键角色。然而，优化过程的质量与时间复杂度差异显著，尤其对于实际相关的大规模量子电路而言。由此催生出声称能比所谓可信编译器提供更优更快复杂量子电路优化的第三方（通常低可信度/不可信）编译器。但不可信编译器可能引发严重安全风险，例如窃取内嵌于量子电路中的敏感知识产权。我们提出一种利用随机可逆门保护量子电路免受此类编译过程中攻击的混淆技术。其核心思想是在原始电路中插入小型随机电路后提交给不可信编译器。由于电路功能被破坏，攻击者可能获取错误知识产权，但用户编译后也将得到错误输出。为规避此问题，我们在编译电路后串联随机电路的逆电路以恢复原始功能。通过在基准电路集上开展全面实验并计算总变差距离度量来评估混淆质量，我们验证了该方法的实用性。该方法实现的总变差距离最高达1.92，性能较先前报道的混淆方法至少提升2倍。同时我们提出新型对抗逆向工程方法，并证明所提混淆方案能抵御逆向工程攻击。该技术对保真度的退化影响极小（平均约1%~3%）。