Quantum Circuit Knitting with Gate Cuts to Reduce Sampling Overhead
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Solution Overview
Problem
Existing methods for cutting gates or wires in quantum circuits result in significant sampling overhead, which scales exponentially with the number of cuts, making it challenging to efficiently divide quantum circuits into smaller sub-circuits.
Innovation Solution
A computer-implemented method and system that separates a quantum circuit into two or more sub-circuits by cutting a quantum gate, allowing the application of gates inside the cut wires without additional sampling overhead, thereby reducing the computational resources and sampling costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If quantum circuits are divided into sub-circuits by cutting gates or wires, then the circuits can be simplified and run on smaller devices, but the sampling overhead scales exponentially with the number of cuts
Solution Approach 1:
The patent applies segmentation by dividing a quantum circuit into multiple sub-circuits through wire cuts, allowing each sub-circuit to be executed independently on smaller quantum devices. The circuit is partitioned such that entangled qubits are distributed across different sub-circuits, with classical communication channels established to maintain quantum correlations between cut qubits.
Solution Approach 2:
The patent introduces classical communication as an intermediary mechanism to bridge the gap between cut qubits in different sub-circuits. By using classical communication channels to transmit measurement results and coordinate operations between sub-circuits, the system maintains the functional equivalence of the original entangled quantum circuit while avoiding the exponential sampling overhead of traditional cutting methods.
2Volume of moving object
If multiple wire cuts are made to simplify the quantum circuit, then the circuit can be executed on smaller devices, but the computational resources and sampling costs increase significantly
Solution Approach 1:
The patent segments the quantum circuit into multiple independent sub-circuits that can be executed on smaller quantum devices with fewer qubits. Each sub-circuit processes a portion of the original circuit's logic, and the segmentation is optimized to minimize the number of classical communication requirements while maintaining computational correctness.
Solution Approach 2:
Each sub-circuit is designed to be self-contained and executable independently, with all necessary quantum operations performed locally within the sub-circuit. The sub-circuits only require classical communication for coordination, eliminating the need for expensive long-range quantum connections and reducing the overall computational resource requirements.
3Device complexity
If gates are cut from the quantum circuit, then the circuit can be simplified, but applying gates inside cut wires requires additional sampling overhead
Solution Approach 1:
The patent extracts quantum gates from the physical circuit implementation and relocates them to the classical post-processing stage. By removing gates from the quantum circuit portion and applying them classically to measurement results, the system eliminates the need for additional quantum operations that would increase sampling overhead, while still achieving the desired computational transformation.
Solution Approach 2:
The patent uses classical computation as an intermediary to apply gate operations that would otherwise require quantum hardware. By translating quantum gate operations into equivalent classical transformations of measurement results, the system avoids the exponential sampling overhead associated with implementing gates on cut qubits, maintaining efficiency while achieving the same computational effect.
Data Source
AI summary
A computer-implemented method for quantum circuit knitting can divide a quantum circuit into two or more sub-circuits. The method includes receiving, on a classical computer, a quantum circuit, and separating, also on the classical computer, the quantum circuit into a first quantum circuit and a second quantum circuit. The separation occurs along a quantum gate and the first quantum circuit and second quantum circuit do not include the quantum gate. On a quantum computer, the first quantum circuit can be performed and a result can be obtained. On the classical computer, the quantum gate can be applied to the result, creating a modified result and, on a quantum computer, the second quantum circuit can be performed using the modified result. The method can reduce the sampling cost for cutting the quantum circuit as compared to conventional quantum circuit cutting techniques.