Gralmonium: Granular Aluminum Nano-Junction Fluxonium Qubit

Abstract

Mesoscopic Josephson junctions (JJs), consisting of overlapping superconducting electrodes separated by a nanometer thin oxide layer, provide a precious source of nonlinearity for superconducting quantum circuits and are at the heart of state-of-the-art qubits, such as the transmon and fluxonium. Here, we show that in a fluxonium qubit the role of the JJ can also be played by a lithographically defined, self-structured granular aluminum (grAl) nano-junction: a superconductor-insulator-superconductor (SIS) JJ obtained in a single layer, zero-angle evaporation. The measured spectrum of the resulting qubit, which we nickname gralmonium, is indistinguishable from the one of a standard fluxonium qubit. Remarkably, the lack of a mesoscopic parallel plate capacitor gives rise to an intrinsically large grAl nano-junction charging energy in the range of tens of $\mathrm{GHz}$, comparable to its Josephson energy $E_{\mathrm{J}}$. We measure average energy relaxation times of $T_1=10\mu \mathrm{s}$ and Hahn echo coherence times of $T_2^{\text{echo}}=9\mu \mathrm{s}$. The exponential sensitivity of the gralmonium to the $E_{\text{J}}$ of the grAl nano-junction provides a highly susceptible detector. Indeed, we observe spontaneous jumps of the value of $E_{\text{J}}$ on timescales from milliseconds to days, which offer a powerful diagnostics tool for microscopic defects in superconducting materials.

References in corpus (20)

• Charge insensitive qubit design derived from the Cooper pair box
• Circuit Quantum Electrodynamics
• Microwave photonics with superconducting quantum circuits
• Quantum technologies with hybrid systems
• Resolving catastrophic error bursts from cosmic rays in large arrays of superconducting qubits
• Coherent manipulation of an Andreev spin qubit
• Electric field spectroscopy of material defects in transmon qubits
• Quantum breakdown of superconductivity in low-dimensional materials
• Fluxonium: an alternative qubit platform for high-fidelity operations
• Improving wafer-scale Josephson junction resistance variation in superconducting quantum coherent circuits
• Implementation of a transmon qubit using superconducting granular aluminum
• Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes
• A gate-tunable, field-compatible fluxonium
• Superconducting granular aluminum resonators resilient to magnetic fields up to 1 Tesla
• Non-degenerate parametric amplifiers based on dispersion engineered Josephson junction arrays
• Quantum non-demolition dispersive readout of a superconducting artificial atom using large photon numbers
• Granular superconductors for high kinetic inductance and low loss quantum devices
• Magnetic-field resilience of 3D transmons with thin-film Al/AlO${}_x$/Al Josephson junctions approaching 1 T
• Geometric superinductance qubits: Controlling phase delocalization across a single Josephson junction
• Onset of phase diffusion in high kinetic inductance granular aluminum micro-SQUIDs

Cited by in corpus (25)

• Fano Interference in Microwave Resonator Measurements
• Observation of giant two-level systems in a granular superconductor
• Granular Aluminum Parametric Amplifier for Low-Noise Measurements in Tesla Fields
• Strong Charge-Photon Coupling in Planar Germanium Enabled by Granular Aluminium Superinductors
• Thermometry Based on a Superconducting Qubit
• Spin Environment of a Superconducting Qubit in High Magnetic Fields
• Dephasing in Fluxonium Qubits from Coherent Quantum Phase Slips
• The effects of disorder in superconducting materials on qubit coherence
• Bloch oscillations in a transmon embedded in a resonant electromagnetic environment
• Temperature dependence of microwave losses in lumped-element resonators made from superconducting nanowires with high kinetic inductance
• Pure kinetic inductance coupling for cQED with flux qubits
• Operation of a high-frequency, phase-slip qubit
• Quantum Coherence in Superconducting Vortex States
• Observation of Perfect Absorption in Hyperfine Levels of Molecular Spins with Hermitian Subspaces
• Kinetic inductance coupling for circuit QED with spins
• Parameter optimization for the unimon qubit
• Study of Magnetic Field Resilient High Impedance High-Kinetic Inductance Superconducting Resonators
• Influence of growth parameters on the superconducting transition temperature in granular aluminum films
• Development of TiN/AlN-based superconducting qubit components
• Time domain non-linear quantum interferometry
• Scalable Low-overhead Superconducting Non-local Coupler with Exponentially Enhanced Connectivity
• Encapsulation epitaxy of air-stable monolayer superconducting films for quantum circuits and qubits
• Scanning tunneling spectroscopy of superconducting nitridized aluminum thin films
• Tuning of superconducting properties with disorder in NbxSn nanocrystalline thin films
• Thermal cycling -- evidence for a generalized tunneling model and a tool to distinguish noise sources in quantum circuits