Qubit Gate Fidelity Determination in Multi-Qubit Quantum Chips
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Solution Overview
Problem
Current technologies are unable to determine the fidelity of two-qubit gates in a multi-bit environment, as they only consider isolated two-qubit gates, ignoring interactions with environmental qubits.
Innovation Solution
A method is provided to determine the fidelity of a qubit gate in a quantum processor by acquiring environmental qubit gates associated with a two-qubit gate, constructing a first target matrix and a corresponding evolution matrix, and using these to calculate the fidelity based on the number of environmental qubits, target matrix, and evolution matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only isolated two-qubit gates are considered in the design process, then the device complexity is reduced and measurement is simplified, but the measurement precision of fidelity in multi-qubit environment deteriorates to the point of being unable to determine fidelity
Solution Approach 1:
The patent segments the complex multi-qubit fidelity measurement problem into manageable components by introducing environmental qubit gates that represent interactions with surrounding qubits. The two-qubit gate fidelity is separated from environmental interactions, allowing each to be characterized independently while accounting for their relationship through the density matrix formalism.
Solution Approach 2:
The patent uses the density matrix as an intermediary mathematical tool to bridge the isolated two-qubit gate characterization and the multi-qubit environmental interactions. The density matrix allows the fidelity to be calculated while accounting for environmental qubit gates without requiring direct measurement of the entire complex multi-qubit system.
2Measurement precision
If environmental qubit gates are included in fidelity determination, then the measurement precision of fidelity in multi-qubit environment is improved, but the device complexity and calculation complexity increase
Solution Approach 1:
The patent extracts the environmental interaction effects from the overall fidelity measurement by introducing environmental qubit gates that specifically represent interactions with surrounding qubits. This extraction allows the fidelity to be calculated by focusing on the two-qubit gate while separately accounting for environmental effects through the density matrix, rather than attempting to measure the entire complex system directly.
Solution Approach 2:
The patent changes the measurement parameters by introducing environmental qubit gates with specific interaction parameters (coupling strengths, interaction times) that characterize the environmental effects. By parameterizing the environmental interactions, the fidelity can be determined through calculations involving these parameters rather than through direct complex measurements.
Data Source
AI summary
This disclosure discloses a method for determining fidelity of a qubit gate in a quantum chip, and a storage medium. The method includes: determining environmental qubit gates associated with a two-qubit gate in the quantum chip, where the two-qubit gate interacts with the environmental qubit gates in the quantum chip; determining, based on the two-qubit gate and the environmental qubit gates, a first target matrix and a corresponding first evolution matrix, where the first target matrix is a diagonal matrix constructed based on a logic gate, and the first evolution matrix is a matrix obtained after time-dependent evolution; and determining the fidelity of the two-qubit gate based on the number of the environmental qubit gates associated with the two-qubit gate, the first target matrix, and the first evolution matrix. This disclosure solves the technical problem of being unable to determine the fidelity of the two-qubit gate.