Flux Qubit Coupling Lattice for Dense Low-Crosstalk Interconnects
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Solution Overview
Problem
Existing quantum computing architectures face challenges in achieving high qubit density, interconnectedness, and computational power due to limitations in qubit coupling and hardware requirements, leading to inefficiencies in problem-solving capabilities.
Innovation Solution
The use of co-planar waveguide flux qubits with inductive coupling and specific lattice structures, such as orthogonal arrays and tiling of unit cells, to increase qubit density and interconnectedness, reducing hardware requirements and crosstalk while maintaining flexibility for scalable designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional qubit coupling architectures are used, then hardware requirements are met, but qubit density and interconnectedness are limited
Solution Approach 1:
The patent transitions from conventional one-dimensional or two-dimensional qubit arrangements to a three-dimensional lattice structure. Multiple arrays of qubits are positioned at different heights (z-dimension) and coupled through vertical couplers, enabling spatial utilization in three dimensions. This dimensional expansion allows significantly higher qubit density without proportionally increasing horizontal hardware footprint, resolving the contradiction between qubit quantity and device complexity.
Solution Approach 2:
The patent implements a hierarchical nesting structure where unit cells containing multiple qubits and couplers are arranged in repeating patterns. Each unit cell is a self-contained module that can be nested within larger arrays, with inner qubits coupled to outer qubits through shared couplers. This nesting approach enables scalable expansion of qubit density while reusing coupling infrastructure, reducing the proportional increase in hardware requirements.
2Adaptability or versatility
If qubit arrays are arranged to form lattice structures, then interconnectedness and treewidth are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent divides the quantum processor into discrete unit cells, each containing a specific arrangement of qubits and couplers. Each unit cell is designed as an independent manufacturable module with standardized dimensions and coupling interfaces. This segmentation allows manufacturing precision to be achieved at the unit cell level rather than requiring precision across the entire large-scale array, making high interconnectedness achievable without proportionally increasing overall manufacturing difficulty.
Solution Approach 2:
The patent employs different coupling configurations at different locations within the lattice structure. Vertical couplers connect qubits across different z-heights, while horizontal couplers connect qubits within the same array plane. The coupling strength and geometry are locally optimized based on position, with closer qubits using stronger coupling and farther qubits using weaker coupling. This local quality approach enables high interconnectedness while accommodating variations in manufacturing precision across different regions of the device.
3Power
If couplers are positioned adjacent to qubit pairs, then coupling efficiency is improved, but crosstalk between qubits increases
Solution Approach 1:
The patent introduces couplers as intermediary elements between qubits that mediate the interaction. Rather than direct qubit-to-qubit coupling, the couplers act as controlled intermediaries that enable coupling only when activated. The couplers are positioned to provide strong coupling when needed but can be decoupled to eliminate unwanted interactions. This intermediary approach maintains high coupling efficiency for intended interactions while preventing crosstalk between non-intended qubit pairs.
Solution Approach 2:
The patent implements dynamically controllable coupling through flux-biased SQUID couplers that can be switched between coupled and decoupled states. The coupling strength is not fixed but can be adjusted in real-time based on computational requirements. This dynamic control allows the system to activate coupling only when and where needed for the current computational step, maintaining high efficiency while minimizing crosstalk during different phases of quantum annealing or gate operations.
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 enhances qubit density, improves computational power by increasing treewidth and conductance, and reduces the probability of getting trapped in undesired states, enabling more complex problem-solving capabilities in quantum computers.
Implementation Method 1
A coupler is positioned adjacent to a pair of qubits such that the coupler inductively couples a co-planar waveguide of the first qubit to a co-planar waveguide of the second qubit
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A quantum computing device includes: a first array of qubits arranged along a first axis; and a second array of qubits arranged along a second axis different from the first axis so that the qubits of the second array intersect with the qubits of the first array to form a lattice structure, in which each qubit in the first array is offset along the second axis relative to a directly adjacent qubit in the first array, each qubit in the second array is offset along the first axis relative to a directly adjacent qubit in the second array, and each intersection between a qubit from the first array and a qubit from the second array in the lattice structure comprises a coupler arranged to inductively couple the qubit from the first array to the qubit from the second array.