Surface Engineering for Qubits - White Paper

White Paper
Surface Engineering for High Performance Qubits

Many of quantum computing’s leading researchers and companies have studied the impact of surface engineering on superconducting resonator and qubit performance.

The body of literature in this area shows that the performance of even the simplest element of quantum computers, the superconducting LC resonator, is dramatically impacted by subtle details of device fabrication. Surfaces are known to be critical to the fabrication of high-performance quantum devices of all kinds, including colour centres, ion traps (which can suffer from surface electric field noise), photonics, and quantum dots.

There are three critical surfaces, or interfaces, that must be controlled in order to make high quality superconducting resonators and qubits. These are:

the superconducting metal-substrate interface (MS),
the superconducting metal-air interface (MA) and
the substrate-air interface (SA).

This whitepaper will focus on superconducting quantum devices, but many of the principles and strategies used to optimize interfaces for these systems are also relevant for devices of all kinds, both quantum and classical. Also, we will review how surfaces and interfaces have a strong effect on losses and how plasma processing can be used to control those losses.