Increasing grain size of polycrystalline superconducting materials for superconducting circuits

A method of increasing grain size of polycrystalline superconducting materials for superconducting circuits, comprising:

• forming an initial superconducting epitaxial layer lattice matched to a substrate formed of a substrate material, the initial superconducting epitaxial layer formed of a compound including the substrate material and a first metal;
• and
• forming a second layer of the first metal on the initial superconducting epitaxial layer and heating the layers to increase a thickness of the initial superconducting epitaxial layer formed of the compound.

A method of increasing grain size of polycrystalline superconducting materials for superconducting circuits, comprising:

• forming a diffusion enhancer layer, comprising a first superconducting metal, on a substrate;
• depositing a second superconducting material on the diffusion enhancer layer at a deposition temperature in a temperature range including the melting temperature of the diffusion enhancer layer such that diffusion of the second superconducting material is enhanced within the diffusion enhancer layer, and a grain size of the second superconducting material is increased.

A method of increasing grain size of polycrystalline superconducting materials for superconducting circuits, comprising:

• setting a grain structure of superconducting elements in a quantum circuit using a separation of phase of elements in the superconducting elements which are fully miscible at higher temperatures and not miscible at lower temperatures.

A method of increasing grain size of polycrystalline superconducting materials for superconducting circuits, comprising:

• heating a mixture, the mixture including a first superconducting material and a second material that does not form intermetallic and are not miscible at room temperature, to a first temperature where the first superconducting material and the second material become miscible;
• and
• cooling the mixture to a second temperature where the first superconducting material and the second material are not miscible any longer, wherein the cooling is performed such that two materials phase separate into their respective crystal structures.