Cryogenic Microwave Filter Structure for Thermal Decoupling
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Solution Overview
Problem
Existing microwave filters fail to operate effectively at cryogenic temperatures below 77 K due to thermal noise from heat flow within conductive materials and significant Kapitza resistance at material interfaces, leading to degraded performance of superconducting qubits in quantum computing devices.
Innovation Solution
A thermally decoupled cryogenic microwave filter device with discontinuous conductive lines separated by a dielectric wall, reducing heat flow and Kapitza resistance by increasing surface contact area between the conductive line and substrate, utilizing materials with high thermal conductivity like sapphire or diamond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous conductive lines are used in microwave filters at cryogenic temperatures, then electrical connectivity is maintained, but thermal noise increases due to heat flow along the conductive path
Solution Approach 1:
The conductive line is divided into multiple discrete segments separated by dielectric materials. This segmentation breaks the continuous thermal conduction path while maintaining electrical functionality through capacitive coupling between segments, thereby reducing thermal noise while preserving electrical connectivity.
2Productivity
If conventional microwave filters are used at cryogenic temperatures below 77 K, then filter operation is attempted, but performance degrades due to Kapitza resistance at material interfaces
Solution Approach 1:
The patent changes the thermal and electrical parameters of the filter structure by using superconducting materials with specific critical temperatures and dielectric materials with optimized thermal conductivity. This parameter optimization reduces Kapitza resistance effects and improves filter performance at cryogenic temperatures below 77 K.
3Loss of energy
If elements of microwave filter become superconductive at cryogenic temperatures, then electrical resistance decreases, but the filter loses its ability to pass, filter, or attenuate signals based on frequency
Solution Approach 1:
Different parts of the filter structure are assigned different material properties: superconducting materials are used for conductive elements where low resistance is needed, while dielectric materials with appropriate loss tangent are used in resonant structures where frequency selectivity is required. This local differentiation maintains both low loss and frequency filtering capabilities.
4Ease of operation
If signal conductors cross temperature zones from room temperature to cryogenic environments, then signal transmission is enabled, but thermal noise degrades performance due to temperature differences of up to 300 K
Solution Approach 1:
Dielectric materials serve as thermal intermediaries between the room-temperature and cryogenic portions of the signal conductor. These dielectrics have low thermal conductivity that blocks heat flow while allowing electrical signal transmission through capacitive coupling, thereby reducing thermal noise in the cryogenic section.
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
The solution significantly reduces thermal noise and Kapitza resistance, enhancing the performance of microwave filters at low temperatures, leading to improved coherence times and reduced qubit errors in quantum computing architectures.
Implementation Method 1
The wall can facilitate propagation of a microwave signal between the first segment and the second segment and can reduce heat flow between the first segment and the second segment of the conductive line
Implementation Method 2
a second distinct technical problem arises due to difficulties associated with heat flow between different materials. The second technical problem arises due to a phenomenon known as Kapitza resistance, which tends to be negligible at room temperature or above cryogenic temperatures but can become very significant at cryogenic temperatures
Implementation Method 3
utilizing materials with high thermal conductivity like sapphire or diamond
Implementation Method 4
The wall can facilitate propagation of a microwave signal between the first segment and the second segment
Data Source
AI summary
An architecture for, and techniques for fabricating, a thermal decoupling device are provided. In some embodiments, thermal decoupling device can be included in a thermally decoupled cryogenic microwave filter. In some embodiments, the thermal decoupling device can comprise a dielectric material and a conductive line. The dielectric material can comprise a first channel that is separated from a second channel by a wall of the dielectric material. The conductive line can comprise a first segment and a second segment that are separated by the wall. The wall can facilitate propagation of a microwave signal between the first segment and the second segment and can reduce heat flow between the first segment and the second segment of the conductive line.