Hybrid Quantum-Classical System for Energy Derivative Computation
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Solution Overview
Problem
Current methods for quantum chemistry calculations, such as VQE and quantum phase estimation, do not effectively compute derivative functions of energy, which are crucial for determining non-time-dependent physical and chemical properties.
Innovation Solution
A hybrid system comprising a classical computer and a quantum computer employs a Variational Quantum Eigensolver (VQE) to generate quantum circuits, with the classical computer processing measurement results to compute derivative functions of energy by incorporating rotation gates into the quantum circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quantum phase estimation is used to calculate derivative functions of energy, then measurement precision can be improved, but device complexity and computational overhead increase significantly
Solution Approach 1:
The patent divides the calculation of derivative functions into separate measurement processes. Instead of using complex quantum phase estimation for derivatives, the method segments the problem into: (1) obtaining energy eigenvalues through VQE, and (2) calculating derivatives classically from finite differences of energy values at different parameter points. This segmentation reduces quantum circuit complexity while maintaining calculation precision.
Solution Approach 2:
The patent introduces classical computation as an intermediary between quantum energy calculation and derivative determination. Rather than directly computing derivatives quantum mechanically, the method uses classical finite difference calculations on quantum-computed energy values, thereby reducing quantum device complexity while achieving the desired derivative functions.
2Ease of operation
If VQE is used to compute energy eigenvalues, then ease of operation is improved, but the ability to compute derivative functions of energy deteriorates
Solution Approach 1:
The patent makes the VQE-based quantum system multi-functional by combining it with classical post-processing. The quantum computer performs energy eigenvalue calculations via VQE, while the classical computer computes derivative functions from these energy values. This universal approach allows the same quantum system to provide both energy information and its derivatives, enhancing versatility without complicating the quantum operation.
Solution Approach 2:
Classical computation serves as an intermediary that extends the functionality of the VQE quantum system. By calculating derivative functions classically from quantum-computed energy values, the method enables the quantum system to provide not only energy eigenvalues but also their derivatives, thereby improving adaptability while maintaining ease of quantum operation.
3Adaptability or versatility
If quantum circuits are extended to compute derivative functions directly, then adaptability is improved, but loss of time and computational resources increases
Solution Approach 1:
The patent segments the computational tasks by performing only energy eigenvalue calculations on the quantum computer using VQE, then computing all derivative functions classically from these energy values. This avoids the time-consuming extension of quantum circuits for direct derivative computation, reducing quantum computation time while maintaining the ability to obtain all necessary derivative functions.
Data Source
AI summary
A classical computer outputs a Hamiltonian and initial information of a parameter expressing a quantum circuit. The classical computer, according to a parameter expressing a first quantum circuit that was output from a quantum computer and was generated by quantum computation employing a Variational Quantum Eigensolver (VQE) based on the Hamiltonian and the initial information, generates a parameter expressing a second quantum circuit including a rotation gate and outputs the parameter expressing the second quantum circuit. The classical computer, based on measurement results of quantum computation that were output from the quantum computer and computed according to the parameter expressing the second quantum circuit, based on the Hamiltonian, and based on a derivative function of the Hamiltonian, generates a derivative function of energy corresponding to the Hamiltonian and outputs the derivative function of energy.