Abstract
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.
Highlights
In the last three decades, atomistic simulations based on the solution of the basic equation of quantum mechanics have played an increasingly important role in predicting the properties of functional materials, encompassing catalysts and energy storage systems for energy applications, and materials for quantum information science
We present a quantum embedding theory built on density functional theory (DFT), which is scalable to large systems and which includes the effect of exchange-correlation interactions of the environment on active regions, going beyond commonly adopted approximations
The embedding theory developed here aims at constructing an effective Hamiltonian operating on an active space (A), defined as derived from the quantum embedding theory, we investigated a subspace of the single-particle Hilbert space: the strongly-correlated electronic states of the NV center in diamond using quantum phase estimation algorithm (PEA)[8,48] and variational quantum eigensolvers (VQE)[49,50,51], and we show that quantum simulations yield results in agreement with those obtained with classical full configuration interaction (FCI) calculations
Summary
In the last three decades, atomistic simulations based on the solution of the basic equation of quantum mechanics have played an increasingly important role in predicting the properties of functional materials, encompassing catalysts and energy storage systems for energy applications, and materials for quantum information science. Several theoretical and computational methods have been developed over the years to treat systems exhibiting strongly-correlated electronic states, including dynamical mean-field theory[3,4] and quantum Monte-Carlo[5,6]; in addition, ab initio quantum chemistry methods, traditionally developed for molecules, have been recently applied to solid state problems as well[7]. These approaches are computationally demanding and it is still challenging to apply them to complex materials containing defects and interfaces, even using highperformance computing architectures
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