Latest publications

A new approach to encoding information in a fluxonium qubit extends its relaxation and coherence times, making this platform a promising candidate for future quantum computing applications. The fluxonium quantum bit, or qubit, consists of a superconducting loop interrupted by a Josephson junction, a thin layer of nonsuperconducting material sandwiched between two superconducting layers. Like all qubits, fluxoniums are easily affected by noise and decoherence, which hampers their ability to store information. Even though this qubit was introduced 10 years ago, we have discovered a new way to operate it that can potentially extend its lifetime. The main idea is to encode the two logical states, 0 and 1, using two different parities of the magnetic flux quanta, or fluxons, that enter the superconducting loop. The ground state corresponds to zero fluxon in the loop, while the first excited states are encoded with an odd fluxon number. As the wave functions of 0 and 1 display minimal overlap, our fluxonium has better protection from relaxation compared to a standard fluxonium with the same 0-1 transition frequency while keeping the same order of protection from dephasing. This encoding of quantum information is enabled by a very large inductance, or superinductance, of 1 μH over a few hundred microns. Despite the challenges in fabricating this circuit, our experiments show impressive stability, with qubits exhibiting long relaxation and coherence times (in the 100-microsecond range). This resilience makes our fluxonium qubit a promising candidate for future quantum computing applications. Additionally, this work demonstrates that large superinductances are a powerful tool in developing robust superconducting qubits, expanding their potential for diverse quantum computing applications.