Quantum Circuit Generation via Pauli Operator Partitioning
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Solution Overview
Problem
Current quantum computer compilation strategies are not sufficiently accurate for many computation tasks, particularly due to the poor scalability of Unitary Coupled Cluster (UCC) Ansatz with respect to molecule size, leading to increased computational time and error rates associated with entangling gates.
Innovation Solution
A method involving partitioning multi-qubit Pauli operators into mutually commuting sets, generating Pauli gadgets through Trotterization, diagonalizing these gadgets into phase gadgets, and transforming them into one- and two-qubit native gates to optimize quantum circuit generation, thereby reducing entangling gate count and depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If UCC Ansatz is used for chemical simulations, then chemical accuracy is improved, but circuit depth scales poorly with molecule size leading to increased computational time
Solution Approach 1:
The patent segments the quantum circuit into distinct functional components: UCC Ansatz preparation, Trotterization decomposition into Pauli gadgets, and measurement optimization. This segmentation allows each component to be optimized independently, reducing overall circuit depth while maintaining chemical accuracy.
Solution Approach 2:
The patent changes parameters of the quantum circuit by optimizing the Trotterization step size and the number of Pauli gadget layers. By adjusting these parameters, the circuit achieves chemical accuracy with reduced depth, directly addressing the time vs. accuracy contradiction.
2Measurement precision
If UCC Ansatz is used for chemical simulations, then chemical accuracy is improved, but error rate scales with the number of entangling gates
Solution Approach 1:
The patent applies local quality by optimizing entangling gates in specific regions of the circuit where they are most critical for chemical accuracy. Rather than uniformly reducing all entangling gates, the method selectively places and optimizes them to maintain accuracy while minimizing error accumulation.
Solution Approach 2:
The patent converts the harmful effect of numerous entangling gates into a benefit by using Trotterization to decompose the UCC Ansatz into Pauli gadgets. This decomposition allows for more efficient gate sequences that achieve the same chemical accuracy with fewer entangling operations, thus reducing error rates.
3Ease of manufacture
If conventional compilation strategies are used, then quantum circuits can be generated, but accuracy is insufficient for many computation tasks
Solution Approach 1:
The patent performs preliminary action by pre-computing the Trotterization decomposition of the UCC Ansatz into Pauli gadgets before actual quantum execution. This pre-processing step optimizes the circuit structure in advance, ensuring both ease of generation and high computation accuracy when the circuit is executed on quantum hardware.
Data Source
AI summary
The is provided a computer-implemented method for generating a quantum circuit from a Unitary Coupled Cluster (UCC) Ansatz, wherein the Ansatz represents an excitation of a reference state by a parameterised operator including excitation operators, and wherein the Ansatz includes multi-qubit Pauli operators that are determined from each excitation operator. The method comprises: partitioning the Pauli operators into mutually commuting sets and sequencing the Pauli operators by set; generating Pauli gadgets from the Pauli operators by Trotterization, wherein the Pauli gadgets have a same sequencing by set as the Pauli operators; diagonalising each set of Pauli gadgets to convert the Pauli gadgets into phase gadgets; and transforming the phase gadgets into one- and two-qubit native gates to generate the quantum circuit. Moreover, there is also provided a system that is configured to implement the method.