Modular Qubit Control for Scalable Quantum Calibration

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Solution Overview

Problem

Scalable in-situ qubit calibration during repetitive error detection in quantum computing systems is challenging due to the complexity of large-scale quantum operations and the need for efficient control of multiple qubits, which existing technologies have not adequately addressed.

Innovation Solution

A quantum computing system employing modular control using software-defined modularity and optimal control theory (OCT) routines to compile, calibrate, and execute quantum algorithms across multiple qubits, reducing complexity by generating control sequences for subsets of qubits and utilizing radio frequency control drives near-resonance transitions, allowing for scalable and adaptable quantum computation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If individual quantum logic gates are tuned and calibrated for each qubit, then control precision is improved, but device complexity and calibration time increase significantly for large-scale systems

Engineering Contradiction:
Improvecontrol precisionVSAvoidcalibration complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the quantum processor into multiple cores, where each core is a manageable subset of qubits. Control sequences are generated and calibrated for each core independently rather than for the entire quantum processor. This segmentation reduces the calibration complexity from exponential scaling with total qubit number to linear scaling with core number, while maintaining control precision through targeted OCT routines on each segment.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies optimal control theory routines to subsets of qubits (cores) rather than attempting to control all qubits simultaneously. This partial action approach allows for precise calibration of control parameters on manageable subsets, avoiding the combinatorial explosion of parameters that would result from full-system calibration, while still achieving high-fidelity operation across the entire quantum processor.

Inventive Principle:
Principle #16Partial or excessive action

2Ease of operation

If control sequences are generated for all qubits simultaneously, then quantum algorithm execution is simplified, but computational complexity and memory requirements become unmanageable

Engineering Contradiction:
Improvealgorithm executionVSAvoidcontrol sequence complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent divides the quantum algorithm execution into segments corresponding to different cores. Each core executes its own control sequence independently, and the overall algorithm is composed by coordinating these segmented executions. This approach maintains ease of operation by allowing independent optimization of each core's control sequence while reducing overall complexity through modular organization.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces a new dimension of organization by arranging qubits into a two-dimensional core array rather than a flat one-dimensional list. This dimensional change allows for efficient memory access patterns and parallel execution of multiple cores, reducing the computational complexity of generating and managing control sequences while maintaining ease of algorithm execution through structured organization.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Device complexity

If a universal set of control parameters is used for all qubits, then system simplicity is maintained, but control accuracy and fidelity decrease for large-scale operations

Engineering Contradiction:
Improvecontrol system simplicityVSAvoidquantum operation fidelity
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent implements local quality by assigning specific control parameters to each core rather than using a universal set for all qubits. Each core develops its own optimized control parameters through OCT routines, allowing for high-fidelity operations tailored to the specific characteristics of each qubit subset. This local customization maintains reliability while managing complexity through the modular core structure.

Inventive Principle:
Principle #3Local quality

4Measurement precision

If full calibration of all qubits is performed, then overall system accuracy is improved, but calibration time and resource consumption scale poorly

Engineering Contradiction:
Improvesystem accuracyVSAvoidcalibration time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent segments the calibration process into independent tasks for each core, allowing parallel calibration of multiple cores simultaneously. This reduces total calibration time from O(N) sequential operations to O(N/P) parallel operations where P is the number of processors, while maintaining system accuracy through comprehensive calibration of all cores. The segmented approach also enables incremental calibration, where cores can be calibrated and tested independently.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary calibration of individual cores before integrating them into the full quantum processor. This preliminary action allows for efficient optimization of each core's control parameters using OCT routines without the computational burden of calibrating the entire system at once. Once cores are pre-calibrated, they can be quickly integrated and tested, significantly reducing total calibration time while maintaining high system accuracy.

Inventive Principle:
Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables efficient compilation and execution of quantum algorithms with high fidelity across large-scale quantum processors, reducing the complexity of large-scale quantum operations and achieving high degrees of parallelism, thereby improving the scalability and adaptability of quantum computing systems.

Implementation Method 1

radio frequency (RF) control drives are applied to the qubits near or on-resonance with a multitude of transitions simultaneously

Methodology Applied
Scientific EffectResonance: Resonance

Data Source

PatentEP3593297B1Modular control in a quantum computing system
Publication Date: 2024.06.19 RIGETTI & CO INC
  • EP3593297B1 patent drawingFigure 1
  • EP3593297B1 patent drawingFigure 2
  • EP3593297B1 patent drawingFigure 3A~3B

AI summary

In a general aspect, a quantum computing method is described. In some aspects, a control system in a quantum computing system assigns subsets of qubit devices in a quantum processor to respective cores. The control system identifies boundary qubit devices residing between the cores in the quantum processor and generates control sequences for each respective core. A signal delivery system in communication with the control system and the quantum processor receives control signals to execute the control sequences, and the control signals are applied to the respective cores in the quantum processor.