Superinductance for very long-lived quantum coherence

Research Project, 2013 – 2014

I will develop a “superinductor” – a very-high kinetic inductance superconducting nanowire of thin-film niobium nitride. Its reactive impedance will exceed the quantum resistance (6.5 kΩ) at microwave frequencies, while being nearly lossless at dc. I shall first make this new component, and then design a new type of superconducting qubit (quantum bit of information) – the “metastable flux qubit” – consisting of a nanoscale Josephson junction (JJ) shunted by a superinductance.

This qubit has a very small transition dipole matrix element between its metastable quantum ground states, and therefore extremely small coupling to any noise sources. This enables a projected energy-relaxation coherence time approaching one second – more than three orders of magnitude better than any existing device. Since decoherence is the worst problem impeding the advancement of quantum-information processing (QIP) technology, the successful realization of this long-lived qubit would represent a breakthrough in superconducting quantum engineering.