Qubit Chip Stud Bump Assembly for Post-Measurement Frequency Tuning
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Solution Overview
Problem
The challenge in producing quantum computer chips is the innate frequency spread of fixed-frequency qubits, leading to frequency collisions and slow cross resonance gates due to large detuning, which is exacerbated by the inability to access qubits for post-measurement frequency modification after flip chip bonding to an interposer chip.
Innovation Solution
A method involving bonding a qubit chip to a test interposer chip, performing frequency measurements at low temperature, pulling apart, modifying qubit frequencies, and then bonding to a device interposer chip, allowing for precise frequency adjustment and preventing frequency collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flip chip bonding is used to assemble qubit chip to interposer chip, then measurement capability is achieved, but post-measurement frequency modification becomes impossible
Solution Approach 1:
The bonding interface is segmented into two distinct types: study bumps for electrical connection and metallic pads without bumps for access points. This segmentation allows simultaneous achievement of measurement capability through study bumps and post-measurement modification capability through accessible metallic pads, resolving the contradiction between bonding integrity and future accessibility.
Solution Approach 2:
Metallic pads serve as intermediary elements that provide dual functionality: they enable electrical connection through study bumps while also serving as accessible interfaces for post-measurement frequency modification. These intermediary pads bridge the gap between the need for stable bonding and the need for future accessibility.
2Ease of manufacture
If qubit frequency is not modified after fabrication, then manufacturing process is simple, but frequency collisions occur reducing chip functionality
Solution Approach 1:
Frequency modification capability is built into the manufacturing process from the beginning through the design of accessible metallic pads and study bumps. This preliminary preparation enables post-measurement tuning without requiring complex additional steps, maintaining ease of manufacture while ensuring reliability by preventing frequency collisions.
Solution Approach 2:
The system allows for parameter changes (qubit frequency) after fabrication by providing accessible metallic pads that enable post-measurement frequency modification. This resolves the contradiction by showing that frequency adjustment is integrated into the manufacturing process rather than being a separate complex operation.
3Measurement precision
If all metallic studs are bonded to test solder bumps, then measurement access is achieved, but subsequent device bonding becomes difficult
Solution Approach 1:
The bonding interface is segmented into two distinct types: study bumps for electrical connection and metallic pads without bumps for access points. This segmentation allows simultaneous achievement of measurement capability through study bumps and post-measurement modification capability through accessible metallic pads, resolving the contradiction between bonding integrity and future accessibility.
Data Source
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AI summary
According to an embodiment of the present invention, a method of producing a quantum computer chip includes performing a frequency measurement on a qubit chip bonded to a test interposer chip for qubits on the qubit chip at an operating temperature of the qubit chip. The method further includes pulling the qubit chip apart from the test interposer chip after performing the frequency measurement, and modifying a frequency of a subset of qubits after pulling the qubit chip apart from the test interposer chip. The method further includes bonding the qubit chip to a device interposer chip after modifying the frequency of the subset of qubits.