Quantum Chip Unit-Cell Layout for Higher Qubit Connectivity
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Solution Overview
Problem
Existing quantum chips face limitations in connectivity between qubits, particularly due to the maximum number of qubits that can couple to a coupling structure, which restricts the chip's performance and requires additional layers or technologies that degrade performance.
Innovation Solution
A quantum chip design with at least three adjacent unit cells, where only a single qubit from each cell is coupled to a coupling structure, enhancing connectivity without the need for multiple layers or direct qubit-qubit coupling, allowing for higher parallelism and reduced SWAP or MOVE gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple qubits are coupled to the same coupling structure to increase connectivity, then the connectivity between qubits is improved, but the maximum number of qubits that can couple to the coupling structure is limited, restricting further connectivity enhancement
Solution Approach 1:
The quantum chip is divided into multiple unit cells, each containing a coupling structure with a limited number of qubits (e.g., 2-6 qubits per coupling structure). This segmentation allows the overall system to achieve high connectivity through the network of distributed unit cells rather than overloading a single coupling structure, resolving the contradiction between connectivity and coupling capacity limits.
Solution Approach 2:
Unit cells are arranged in a two-dimensional pattern, transitioning from one-dimensional linear coupling to two-dimensional spatial organization. This dimensional expansion enables qubits in different unit cells to interact through multiple pathways, achieving enhanced connectivity without increasing the number of qubits per coupling structure beyond technological limits.
2Adaptability or versatility
If additional layers or flip-chip technology are used to provide long-range connectivity, then the connectivity between spatially distant qubits is enhanced, but the performance of the quantum chip deteriorates due to distribution of elements on different layers
Solution Approach 1:
The patent implements a two-dimensional arrangement of unit cells on a single layer, using spatial distribution in the plane rather than vertical stacking across multiple layers. This approach achieves long-range connectivity through in-plane coupling structures and tunable couplers while maintaining all elements on one layer, avoiding the performance degradation associated with multi-layer architectures.
3Adaptability or versatility
If airbridges are used to provide connectivity, then the connection between qubits is established, but the performance of the quantum chip is reduced
Solution Approach 1:
The patent removes airbridges from the architecture entirely, extracting this harmful element that degrades performance. Instead, conventional planar coupling structures and tunable couplers are used to provide all necessary connectivity, achieving both high connectivity and maintained performance by eliminating the performance-reducing airbridge technology.
4Device complexity
If direct qubit-qubit coupling is used between spatially neighboring qubits, then the simplicity of the structure is maintained, but the connectivity beyond nearest neighbors is limited
Solution Approach 1:
Coupling structures and tunable couplers are introduced as intermediary elements between qubits. These intermediaries enable indirect coupling between qubits that are not spatially adjacent, extending connectivity beyond nearest neighbors while maintaining a relatively simple modular unit cell structure. The intermediaries facilitate long-range interactions without requiring direct qubit-qubit coupling paths.
Data Source
AI summary
A quantum chip including a number of unit cells arranged in a two-dimensional pattern, each unit cell including at least one coupling structure and at least two qubits coupled thereto, wherein there are at least three adjacent unit cells with only a single qubit of the qubits of the at least three adjacent unit cells coupled to the at least one coupling structure of each of the three adjacent unit cells.