Variational Quantum Simulation for Quantum Chemistry. Issue 4 (23rd January 2019) - Li, Yifan
Abstract: Variational quantum‐classical hybrid algorithms are emerging as important tools for simulating quantum chemistry with quantum devices. These algorithms can be applied to evaluate various molecular properties, including potential energy surfaces. Here in, recent progresses on the development of the so‐called variational quantum eigensolver (VQE) are surveyed. The eigensolver aims at reducing the consumption of quantum resources as much as possible. The key feature of VQE is that variation quantum states are optimized by a feedback process, where the measurement of the Hamiltonian is implemented term by term. This approach avoids the need of encoding all of the information about the molecular Hamiltonian in a quantum circuit. The VQE method is also compatible with classical methods in quantum chemistry, such as unitary coupled‐cluster ansatz. Furthermore, basic elements of VQE are covered, such as qubit encoding, mapping rules of the fermionic operators, ansatz preparation, together with several techniques for improving the performance, including constraining, and error mitigation. Abstract : Variational quantum eigensolver is one of the most promising hybrid quantum‐classical algorithms in the field of quantum simulation . It is considered to be implementable in near‐term quantum computers, due to its simplicity, feasibility, and robustness. In this report, recent theoretical progress on these variational algorithms and involved techniques are reviewed.