Quantum Processor Qubit Topology for Complex Graph Embedding
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Solution Overview
Problem
Existing quantum processor architectures, such as those described in U.S. Pat. No. 8,421,053, have limited interaction between unit cells, restricting the complexity and size of problems that can be solved due to fixed qubit interconnections, which hinders the ability to embed certain problem instances effectively.
Innovation Solution
A new quantum processor architecture is designed with increased inter-cell qubit interconnections by arranging qubits in a multi-layered structure where qubits from one set cross qubits in another set, and using controllable coupling devices to facilitate communicative coupling between qubits in the same and adjacent unit cells, allowing for stronger intra-cell and inter-cell interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If qubits are arranged in fixed interconnections within unit cells, then device structure is simplified and easier to manufacture, but interaction between unit cells is limited and problem embedding capability is restricted
Solution Approach 1:
The quantum processor is divided into multiple unit cells, each containing a set of qubits with fixed internal interconnections. This segmentation maintains manufacturing simplicity while enabling scalable expansion. Each unit cell is a self-contained module that can be replicated and tiled to build larger systems.
Solution Approach 2:
The patent introduces a spatial dimension for inter-cell coupling by positioning unit cells in a two-dimensional array and enabling coupling between adjacent cells in horizontal, vertical, and diagonal directions. This dimensional arrangement transforms the limited one-dimensional connectivity into a rich two-dimensional interaction network, significantly enhancing problem embedding capability without complicating individual unit cell structure.
2Adaptability or versatility
If controllable coupling devices are added between qubits in same and adjacent unit cells, then inter-cell interactions are enhanced and more complex problems can be solved, but device complexity increases
Solution Approach 1:
The coupling devices are designed as universal controllable elements that can mediate interactions between any pair of qubits in adjacent unit cells. The same coupling device structure and control mechanism are used throughout the system, providing multi-functional capability. This universality allows a single type of coupling device to handle various interaction scenarios, reducing the variety of components needed and managing complexity through standardization.
Solution Approach 2:
The coupling devices are made dynamically controllable, allowing the interaction strength and connectivity between qubits to be adjusted in real-time. This dynamic control enables the system to reconfigure its effective connectivity pattern to match different problem requirements, providing adaptability without requiring permanent physical reconfiguration of the device structure.
3Adaptability or versatility
If unit cells are positioned to enable horizontal, vertical, and diagonal adjacency, then qubit interconnections between cells are increased and problem embedding is improved, but manufacturing precision requirements increase
Solution Approach 1:
By segmenting the quantum processor into discrete unit cells with standardized interfaces, the patent enables modular assembly. Each unit cell is fabricated as an independent module with defined connection points, allowing for systematic positioning and coupling. This segmentation approach makes it feasible to achieve the required positioning precision through modular manufacturing and assembly processes.
Solution Approach 2:
The patent utilizes two-dimensional spatial arrangement of unit cells to achieve multiple coupling directions (horizontal, vertical, diagonal). By organizing qubits and unit cells in a planar grid structure, the system naturally supports multi-directional connectivity without requiring three-dimensional positioning. This two-dimensional layout simplifies the manufacturing precision requirements compared to true 3D positioning while still enabling rich inter-cell interactions.
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 architecture enhances the ability to solve complex problems by increasing inter-cell interactions, enabling better embedding of problem instances that were difficult to solve with fixed architectures, and allowing for more flexible and efficient quantum computation.
Implementation Method 1
Each qubit comprises a loop of superconducting material interrupted by at least one Josephson junction
Implementation Method 2
each qubit comprises a loop of superconducting material interrupted by at least one Josephson junction
Data Source
AI summary
A problem graph having one or more odd cycles is embedded in a quantum processor. The quantum processor includes a plurality of qubits and coupling devices, each coupling device operable to provide controllable communicative coupling between a respective pair of the plurality of qubits to form an interconnected topology. Embedding may, for example, be realized by mapping each vertex of the problem graph to a respective single qubit; mapping each edge of the problem graph to a respective single coupling device, where for pairs of qubits, each qubit of the pair is mapped to a respective pair of vertices. The problem graph may include one or more sub-graphs, one or more of the sub-graphs being a bipartite K3,3 graph.