Non-Clifford Quantum Gate Noise Characterization With SPAM Robustness

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Solution Overview

Problem

Existing noise characterization methods for quantum gates, particularly non-Clifford gates, are not state preparation and measurement (SPAM)-robust, leading to incompatibility with error-mitigation schemes and reduced accuracy in quantum circuits.

Innovation Solution

A system and method for characterizing noise in non-Clifford quantum gates using a two-qubit quantum circuit with random gate applications and curve fitting of expectation values, enabling SPAM-robust noise characterization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If existing noise characterization methods are used for non-Clifford gates, then the characterization can be performed, but the results are not SPAM-robust leading to reduced accuracy

Engineering Contradiction:

Improvenoise characterization accuracyVSAvoidSPAM robustness

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent inverts the traditional approach by applying random Pauli gates after the non-Clifford gate instead of before. This reverse ordering enables the measurement to become SPAM-robust while maintaining accuracy in noise characterization for non-Clifford gates.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the measurement parameters by introducing random Pauli gates with specific probabilities (p=0.5) and modifying the measurement basis. This parameter transformation allows the system to achieve both SPAM robustness and measurement precision simultaneously.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If quantum circuit depth and width are increased to implement non-Clifford operations, then the computational capability is improved, but system noise increases leading to estimation error

Engineering Contradiction:

Improvequantum circuit capabilityVSAvoidsystem noise

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the traditional mechanical approach of increasing circuit depth and width with a statistical method using random Pauli gates. This substitution allows achieving the same computational capability while reducing the harmful noise effects through probabilistic error cancellation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the harmful noise into a useful signal by using the same noise sources that affect the computation. Through random Pauli gates and curve fitting, the noise characteristics are extracted and can be used to correct future measurements, turning noise from a detrimental factor into a diagnostic tool.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS12524696B2Noise characterization for non-Clifford quantum gates

Publication Date: 2026.01.13 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Systems, computer-implemented methods, and/or computer program products to facilitate noise characterization of a two-qubit unitary are provided. A system can comprise a memory that stores computer executable components and a processor that executes the computer executable components stored in the memory. The computer executable components can comprise an execution component that executes a two-qubit quantum circuit comprising a preparation of an initial state for a two-qubit Pauli operator and an application of one or more circuit layers, wherein each circuit layer comprises an application of a pair of random gates each selected from I, X, Y or Z, application of the two-qubit unitary having a rotation angle modified to have a 50% probability of being each of positive and negative, and another application of the first random gate and the second random gate. A fitting component employs curve fitting of an expectation value resulting from the execution.