Millimetre-Wave Superconducting Quantum Circuits

I propose an experimental program to investigate quantum-coherent properties of superconducting circuits at frequencies one order of magnitude larger than those demonstrated until now.

My idea is to develop a new generation of superconducting qubits with significantly increased energy level separation between their ground and the first excited states. Pushing the operation frequency of superconducting qubits up offers a number of potential technological advantages.

Due to the increased level separation, such novel millimetre-wave quantum processors could be operated at much higher temperatures than their present counterparts.

Even at millikelvin temperatures, the higher qubit resonance frequency will offer better protection from non-thermal noise. Furthermore, qubit logic gates can be performed faster at higher frequencies.

Quantum circuit components can be reduced in size due to smaller wavelength at higher frequencies, thus allowing for a smaller footprint, denser packaging and better integration.

These numerous potential advantages face nevertheless a number of challenges and pose open questions that will be addressed and are aimed to be answered in the proposed project.

The goal is to develop prototype qubits for the 100 GHz frequency range and to demonstrate their manipulation and quantum state tomography. This challenging project will unearth fundamental knowledge about decoherence in this yet unexplored frequency range. We will study dielectric loss and other decoherence sources as functions of frequency and temperature.

Once successful, this approach will open a new way of building a superconducting quantum computer.