Surface Code Qubit Parameter Layout to Reduce Frequency Crowding

Solution Overview

Problem

Existing quantum computing technologies face challenges in optimizing physical parameters for fault-tolerant quantum computing, particularly in reducing frequency crowding and addressing the intrinsic functionality of different qubits in surface code architectures, which affects the performance of quantum error correction.

Innovation Solution

The proposed solution involves configuring quantum error correction circuits with code qubits as long coherence qubits and syndrome qubits as large anharmonicity qubits, where the syndrome qubits are designated as control qubits for all two-qubit gates, optimizing the lattice arrangement to minimize frequency crowding and tolerating measurement errors over gate errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If syndrome qubits are configured as control qubits with large anharmonicity, then frequency crowding is reduced and fault tolerance is improved, but dephasing time decreases

Engineering Contradiction:

Improvefault toleranceVSAvoiddephasing time

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent applies local quality by assigning different functional roles and physical characteristics to different qubit types within the same quantum error correction circuit. Syndrome qubits are configured with large anharmonicity to serve as control qubits for CNOT gates, which reduces frequency crowding and improves fault tolerance. Code qubits are configured with long coherence times to preserve quantum information. This differentiation of local properties (anharmonicity vs. coherence time) based on functional requirements resolves the contradiction between fault tolerance and dephasing time.

Inventive Principle:

Principle #3Local quality

2Duration of action of moving object

If code qubits are configured as target qubits with long coherence times, then quantum information is preserved, but anharmonicity is reduced

Engineering Contradiction:

Improvecoherence timeVSAvoidanharmonicity

Core Design Contradiction:

Duration of action of moving objectVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by assigning different functional roles and physical characteristics to different qubit types within the same quantum error correction circuit. Syndrome qubits are configured with large anharmonicity to serve as control qubits for CNOT gates, which reduces frequency crowding and improves fault tolerance. Code qubits are configured with long coherence times to preserve quantum information. This differentiation of local properties (anharmonicity vs. coherence time) based on functional requirements resolves the contradiction between fault tolerance and dephasing time.

Inventive Principle:

Principle #3Local quality

3Device complexity

If all qubits are configured with similar parameters, then circuit design is simplified, but frequency crowding increases and performance deteriorates

Engineering Contradiction:

Improvecircuit designVSAvoiderror correction performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies local quality by assigning different functional roles and physical characteristics to different qubit types within the same quantum error correction circuit. Syndrome qubits are configured with large anharmonicity to serve as control qubits for CNOT gates, which reduces frequency crowding and improves fault tolerance. Code qubits are configured with long coherence times to preserve quantum information. This differentiation of local properties (anharmonicity vs. coherence time) based on functional requirements resolves the contradiction between fault tolerance and dephasing time.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies segmentation by dividing the quantum error correction circuit into two distinct qubit categories with different optimized parameters: syndrome qubits (control qubits) and code qubits (target qubits). Each segment is independently optimized for its specific function, with syndrome qubits having large anharmonicity for frequency separation and code qubits having long coherence times for information preservation. This segmentation resolves the contradiction between design simplicity and performance by creating specialized subsystems.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9978020B1Optimizing physical parameters in fault-tolerant quantum computing to reduce frequency crowding

Publication Date: 2018.05.22 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A technique relates to quantum error correction. Code qubits are configured as target qubits, and the code qubits have a first dephasing time and a first anharmonicity. Syndrome qubits are configured as control qubits, and the syndrome qubits have a second dephasing time and a second anharmonicity. The target qubits and the control qubits are configured to form one or more controlled not (CNOT) gates. The first dephasing time is greater than the second dephasing time and the second anharmonicity is greater than the first anharmonicity.