A method for fabricating a superconducting coaxial cable for quantum computers includes the following steps: placing an NbTi alloy melt in the lower chamber of a vacuum furnace; preheating a metal capillary mold and placing it in the upper chamber of the vacuum furnace; adjusting the vacuum levels in the lower and upper chambers of the vacuum furnace to draw the NbTi alloy melt into the metal capillary mold; cooling and then opening the mold to remove the NbTi capillary; cold-drawing an NbTi/Cu single-core assembly rod, etching away the copper to obtain NbTi filaments; repeatedly coating and curing the NbTi filaments with PTFE coating material to obtain NbTi filaments with an insulating layer; embedding the NbTi filaments with the insulating layer into the NbTi capillary and welding the joint to obtain the superconducting coaxial cable. This application reduces the fabrication difficulty of the superconducting coaxial cable by combining vacuum casting and coating curing technologies.
The superconducting coaxial cable is obtained by inserting a central conductor into an outer conductor tube, maintaining their coaxial alignment; filling the space between the central conductor and outer conductor tube with resin material and compacting the resin; heating the semi-finished coaxial cable body to foam the resin material and form a dielectric layer; then evacuating the semi-finished product and filling it with inert gas to form an inert gas layer.
However, the above-mentioned prior art focuses on the subsequent processing of the central conductor and outer conductor tube, without addressing the fabrication process of the central conductor and outer conductor tube themselves. Furthermore, the fabrication process of the prior art is relatively complex, making the fabrication of superconducting coaxial cables difficult.
This invention proposes a method for fabricating a superconducting coaxial cable for quantum computers, aiming to address the problem that existing technologies lack reliable fabrication processes that do not address the central conductor and outer conductor tube themselves, resulting in complex fabrication processes and the high difficulty in fabricating superconducting coaxial cables.
On one hand, this invention provides a method for preparing a superconducting coaxial cable for quantum computers, comprising the following steps:
Step 1: Placing purified NbTi alloy melt in a crucible within the lower chamber of a vacuum furnace.
Step 2: Preheating a metal capillary mold and placing it within the upper chamber of the vacuum furnace.
Step 3: Adjusting the vacuum levels in the lower and upper chambers of the vacuum furnace to draw the NbTi alloy melt into the metal capillary mold. After cooling, the mold is opened, and the NbTi capillary is removed.
Step 4: Cold-drawing an NbTi/Cu single-core assembly rod as raw material to obtain an NbTi/Cu single-core wire. After etching away the copper, NbTi filaments are obtained.
Step 5: Repeatedly coating and curing the NbTi filaments with a PTFE coating material to obtain an NbTi filament with an insulating layer.
Step 6: Embedding the NbTi filament with the insulating layer into the NbTi capillary and welding joints at both ends to obtain a superconducting coaxial cable for quantum computers.
In one possible implementation, in step one, the vacuum degree of the lower chamber of the vacuum furnace is controllable within the range of 0.003-0.09 Pa, and the mass ratio of impurities in the purified NbTi alloy melt is less than 0.1%.
In one possible implementation, in step two, the preheating temperature of the metal capillary mold is 1300-1800℃, and the vacuum degree of the upper chamber of the vacuum furnace is controllable within the range of 0.000003-0.003 Pa.
In one possible implementation, in step three, the vacuum degrees of the lower chamber and the upper chamber of the vacuum furnace are adjusted, the vacuum degree ratio of the lower chamber to the upper chamber is between 400-1000, and the rate at which the NbTi alloy melt is drawn into the metal capillary mold is between 1-5 mm/s.
In one possible implementation, in step four, the cold drawing pass rate of the NbTi/Cu single-core assembly rod as raw material is between 5% and 15%, and the final diameter of the NbTi/Cu single-core wire is between 0.1 and 0.9 mm.
In one possible implementation, in step four, the copper removal etching uses a 5-8 mol/L sulfuric acid solution, and the etching time is between 10 and 30 minutes.
In one possible implementation, in step five, the PTFE coating material comprises: 60%-75% PTFE emulsion by mass, 0.2%-0.6% defoamer by mass, 0.2%-0.6% wetting agent by mass, and the balance being high-purity water.
The electrical conductivity of the PTFE coating material at 25°C is less than 0.1 μS/cm.
In one possible implementation, in step five, the curing temperature is 100-250°C, and the number of coating and curing cycles is between 5 and 15.
In one possible implementation, in step six, the NbTi filament with the insulating layer is embedded into the NbTi capillary using a magnetic screwing method.
