Characterization and Reduction of Capacitive Loss Induced by Sub-Micron Josephson Junction Fabrication in Superconducting Qubits

Abstract

Josephson junctions form the essential non-linearity for almost all superconducting qubits. The junction is formed when two superconducting electrodes come within $\sim$1 nm of each other. Although the capacitance of these electrodes is a small fraction of the total qubit capacitance, the nearby electric fields are more concentrated in dielectric surfaces and can contribute substantially to the total dissipation. We have developed a technique to experimentally investigate the effect of these electrodes on the quality of superconducting devices. We use $\lambda$/4 coplanar waveguide resonators to emulate lumped qubit capacitors. We add a variable number of these electrodes to the capacitive end of these resonators and measure how the additional loss scales with number of electrodes. We then reduce this loss with fabrication techniques that limit the amount of lossy dielectrics. We then apply these techniques to the fabrication of Xmon qubits on a silicon substrate to improve their energy relaxation times by a factor of 5.

References in corpus (6)

• Surface codes: Towards practical large-scale quantum computation
• Detecting arbitrary quantum errors via stabilizer measurements on a sublattice of the surface code
• Observation of classical-quantum crossover of 1/f flux noise and its paramagnetic temperature dependence
• Characterization and reduction of microfabrication-induced decoherence in superconducting quantum circuits
• Dielectric surface loss in superconducting resonators with flux-trapping holes
• Complete stabilization and improvement of the characteristics of tunnel junctions by thermal annealing

Cited by in corpus (35)

• Simplified Josephson-junction fabrication process for reproducibly high-performance superconducting qubits
• Quantum dynamics of a few-photon parametric oscillator
• Inductively shunted transmon qubit with tunable transverse and longitudinal coupling
• Precision measurement of the microwave dielectric loss of sapphire in the quantum regime with parts-per-billion sensitivity
• Mitigation of interfacial dielectric loss in aluminum-on-silicon superconducting qubits
• Coherent superconducting qubits from a subtractive junction fabrication process
• Enhancing the Coherence of Superconducting Quantum Bits with Electric Fields
• Magnetic imaging of superconducting qubit devices with scanning SQUID-on-tip
• An argon ion beam milling process for native ${\text{AlO}}_{\text{x}}$ layers enabling coherent superconducting contacts
• Bidirectional multi-photon communication between remote superconducting nodes
• Coupler-Assisted Leakage Reduction for Scalable Quantum Error Correction with Superconducting Qubits
• Circle fit optimization for resonator quality factor measurements: point redistribution for maximal accuracy
• Microwave characterization of tantalum superconducting resonators on silicon substrate with niobium buffer layer
• Mitigating Losses of Superconducting Qubits Strongly Coupled to Defect Modes
• Argon milling induced decoherence mechanisms in superconducting quantum circuits
• Compact superconducting microwave resonators based on Al-AlOx-Al capacitor
• Characterization of process-related interfacial dielectric loss in aluminum-on-silicon by resonator microwave measurements, materials analysis, and imaging
• Josephson traveling-wave parametric amplifier based on low-intrinsic-loss coplanar lumped-element waveguide
• Preserving phase coherence and linearity in cat qubits with exponential bit-flip suppression
• Enhanced Superconducting Qubit Performance Through Ammonium Fluoride Etch
• Realizing a Continuous Set of Two-Qubit Gates Parameterized by an Idle Time
• Superconducting Quantum Simulation for Many-Body Physics beyond Equilibrium
• Material matters in superconducting qubits
• Optical Direct Write of Dolan--Niemeyer-Bridge Junctions for Transmon Qubits
• Fast microwave-driven two-qubit gates between fluxonium qubits with a transmon coupler
• Control and readout of a transmon using a compact superconducting resonator
• Niobium Air Bridges as Low-Loss Components for Superconducting Quantum Hardware
• A practical guide for building superconducting quantum devices
• Optimal design of a superconducting transmon qubit with tapered wiring
• Review of Superconducting Qubit Devices and Their Large-Scale Integration
• Optimizing CMOS-compatible, superconducting titanium nitride resonators: Deposition conditions and structuring processes
• Interacting Defects Generate Stochastic Fluctuations in Superconducting Qubits
• Detecting spins with a microwave photon counter
• Aluminum air bridges for superconducting quantum devices realized using a single step electron-beam lithography process
• Surface Optimization of Superconducting Aluminum Resonators for Robust Quantum Device Fabrication