Quantum Gate Control Trajectories Using Reinforcement Learning

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Solution Overview

Problem

Existing methods for designing quantum gate control sequences in quantum computers fail to effectively address leakage errors and quantum hardware control noise, leading to reduced computational efficiency and fidelity.

Innovation Solution

A reinforcement learning model is applied to design quantum gate control schemes, using a universal quantum control cost function that penalizes leakage and infidelity, and incorporates stochastic training to handle noise, enabling robust and efficient quantum gate implementation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing methods for designing quantum gate control sequences are used, then the quantum gate can be implemented, but leakage errors and quantum hardware control noise cause reduced computational efficiency and fidelity

Engineering Contradiction:
Improvegate fidelityVSAvoidcomputational efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The reinforcement learning model performs preliminary training with stochastic noise incorporated into the training process. The agent learns optimal control trajectories by experiencing noisy environments during training, enabling it to produce noise-robust control sequences before actual quantum gate execution. This preliminary adaptation to noise conditions resolves the contradiction by preparing the control system to maintain fidelity despite hardware noise during actual computation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The reinforcement learning framework implements continuous feedback through the reward function, which evaluates control trajectories based on gate fidelity, leakage errors, and runtime. The agent uses this feedback to iteratively improve its control policies, learning to balance fidelity requirements with computational efficiency. The feedback mechanism enables the system to automatically optimize control sequences that maintain high gate fidelity while minimizing runtime, resolving the contradiction between reliability and productivity.

Inventive Principle:
Principle #23Feedback

2Reliability

If reinforcement learning is applied to design quantum gate control sequences, then robustness against hardware noise is improved, but the training process requires significant computational resources and time

Engineering Contradiction:
Improverobustness against hardware noiseVSAvoidtraining time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The reinforcement learning model performs preliminary training with stochastic noise incorporated into the training process. The agent learns optimal control trajectories by experiencing noisy environments during training, enabling it to produce noise-robust control sequences before actual quantum gate execution. This preliminary adaptation to noise conditions resolves the contradiction by preparing the control system to maintain fidelity despite hardware noise during actual computation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The training process incorporates variable noise parameters and reward function weights that can be adjusted to balance training comprehensiveness with training time. By carefully selecting noise levels and reward priorities, the system achieves sufficient robustness without requiring excessively long training periods. This parameter optimization resolves the contradiction between achieving noise robustness and minimizing training time investment.

Inventive Principle:
Principle #35Parameter changes

3Reliability

If a universal quantum control cost function is used to penalize leakage and infidelity, then gate fidelity is enhanced, but the control sequence complexity increases

Engineering Contradiction:
Improvegate fidelityVSAvoidcontrol sequence complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The reinforcement learning agent learns universal control policies that can handle multiple objectives (minimizing leakage, reducing infidelity, optimizing runtime) through a single unified reward function. This universal approach replaces the need for separate control sequences for each objective, achieving high gate fidelity without proportionally increasing control sequence complexity. The multi-functionality of the learned policy resolves the contradiction by consolidating multiple fidelity-enhancing controls into a unified sequence.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The reward function uses adjustable penalty weights for leakage and infidelity that can be tuned to achieve desired fidelity levels without excessively complicating control sequences. By optimizing these parameter weights, the system achieves high gate fidelity with minimally complex control sequences, resolving the contradiction between fidelity enhancement and control complexity.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP4209971B1Quantum computation through reinforcement learning
Publication Date: 2025.11.26 GOOGLE LLC
  • EP4209971B1 patent drawingFigure 1
  • EP4209971B1 patent drawingFigure 2A~2B
  • EP4209971B1 patent drawingFigure 3

AI summary

Methods, systems, and apparatus for designing a quantum control trajectory for implementing a quantum gate using quantum hardware. In one aspect, a method includes the actions of representing the quantum gate as a sequence of control actions and applying a reinforcement learning model to iteratively adjust each control action in the sequence of control actions to determine a quantum control trajectory that implements the quantum gate and reduces leakage, infidelity and total runtime of the quantum gate to improve its robustness of performance against control noise during the iterative adjustments.