Theory Overview

The theory material is split into focused pages so equations, method families, and implementation assumptions are easier to scan.

(1)\[E_0 \le \langle \psi | H | \psi \rangle\]

The variational algorithms in this repository start from the bound in (1): a parameterized circuit is useful when it can reach low-energy states of the shared qubit Hamiltonian.

(2)\[E(\theta) = \langle \psi(\theta) | H | \psi(\theta) \rangle\]

VQE minimizes (2), while QPE estimates phases of time evolution and VarQITE/VarQRTE project imaginary-time or real-time dynamics onto an ansatz manifold.

• Chemistry and Background
• VQE, Ansatzes, and ADAPT
• Excited-State Methods
• Quantum Phase Estimation
• QITE and QRTE
• Noise Models
• References