Quantum computers hold promise to enable efficient simulations of the properties of molecules and materials; however, at present they only permit ab initio calculations of a few atoms, due to a limited number of qubits. In order to harness the power of near-term quantum computers for simulations of larger systems, it is desirable to develop hybrid quantum-classical methods where the quantum computation is restricted to a small portion of the system. This is of particular relevance for molecules and solids where an active region requires a higher level of theoretical accuracy than its environment. Here, we present a quantum embedding theory for the calculation of strongly-correlated electronic states of active regions, with the rest of the system described within density functional theory. We demonstrate the accuracy and effectiveness of the approach by investigating several defect quantum bits in semiconductors that are of great interest for quantum information technologies. We perform calculations on quantum computers and show that they yield results in agreement with those obtained with exact diagonalization on classical architectures, paving the way to simulations of realistic materials on near-term quantum computers.

量子计算机有望实现对分子和材料特性的高效仿真。但是，由于量子位的数量有限，目前它们仅允许从头算起几个原子。为了利用近期量子计算机的能力来模拟大型系统，希望开发出混合量子经典方法，其中量子计算仅限于系统的一小部分。这对于分子和固体特别重要，在分子和固体中，活性区域比其环境需要更高的理论精度。在这里，我们介绍了一种量子嵌入理论，用于计算有源区的强相关电子态，其余部分在密度泛函理论中进行了描述。我们通过研究半导体中对量子信息技术非常感兴趣的几个缺陷量子位来证明该方法的准确性和有效性。我们在量子计算机上执行计算，结果表明，它们产生的结果与经典体系中精确对角化获得的结果一致，从而为在近期量子计算机上模拟实际材料铺平了道路。