Hybrid Quantum-Classical Computer for Variational Coupled Cluster
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Solution Overview
Problem
Current methods for implementing variational coupled cluster (vCC) techniques on quantum computers are computationally expensive and have not been fully explored, particularly due to difficulties in handling non-unitary operations, limiting their application in strongly correlated systems.
Innovation Solution
A hybrid quantum-classical computer system is developed, utilizing a classical computer to assist a quantum computer in implementing improved vCC methods by generating and executing quantum circuits that realize non-unitary operations through linear combination of unitaries and fixed-point oblivious amplitude amplification, enabling efficient preparation of vCC ansatz states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If variational coupled cluster (vCC) methods are implemented on quantum computers, then ground state energy estimation accuracy is improved, but computational complexity and implementation difficulty increase due to non-unitary operations
Solution Approach 1:
The patent introduces an intermediary classical computer that assists the quantum computer in handling non-unitary operations. The classical computer generates quantum circuits that implement vCC methods, breaking down the complex non-unitary operation into manageable unitary components that can be executed on the quantum device, thus reducing the implementation burden on the quantum computer alone.
Solution Approach 2:
The patent segments the vCC implementation into distinct components: a classical computer that generates quantum circuits and a quantum computer that executes them. This segmentation allows each device to operate in its optimal regime, with the classical computer handling complex algorithm generation and the quantum computer performing the actual quantum simulation, thereby managing overall system complexity.
2Measurement precision
If non-unitary operations are handled directly on quantum computers, then vCC method accuracy is improved, but computational efficiency deteriorates due to lack of optimized algorithms
Solution Approach 1:
The patent replaces direct mechanical execution of non-unitary operations on the quantum computer with a substitution approach: the classical computer generates optimized quantum circuits that implement these operations using standard unitary gates. This substitution enables the quantum computer to execute operations more efficiently using its native unitary gate set, improving computational efficiency while maintaining vCC accuracy.
Solution Approach 2:
The classical computer performs preliminary action by generating the quantum circuit descriptions before execution on the quantum device. This pre-computation of circuit structures allows the quantum computer to execute the vCC methods more efficiently, as the complex algorithmic preparation is done beforehand on the classical system, optimizing the overall computational workflow.
3Ease of operation
If unitary coupled cluster (uCC) methods are used, then implementability on quantum computers is improved, but ground state energy accuracy deteriorates compared to vCC methods
Solution Approach 1:
The patent creates a universal framework that can handle both unitary and non-unitary operations through a single hybrid quantum-classical architecture. The system can implement vCC methods (non-unitary) with high accuracy while maintaining the ease of quantum implementation, effectively making the system multi-functional and capable of achieving both uCC implementability and vCC accuracy simultaneously.
Solution Approach 2:
The classical computer acts as an intermediary that enables the quantum computer to access more powerful vCC methods without sacrificing implementability. By handling the complex circuit generation and non-unitary operation decomposition, the classical intermediary allows the quantum device to focus on execution, achieving both ease of operation and high accuracy.
Data Source
AI summary
A hybrid quantum classical (HQC) computer, which includes both a classical computer component and a quantum computer component, solves linear systems. The HQC decomposes the linear system to be solved into subsystems that are small enough to be solved by the quantum computer component, under control of the classical computer component. The classical computer component synthesizes the outputs of the quantum computer component to generate the complete solution to the linear system.