Why Superconducting Ta Qubits Have Fewer Tunneling Two-Level Systems at the Air-Oxide Interface Than Nb Qubits
arXiv:2405.09842 · doi:10.1103/PhysRevApplied.23.024017
Abstract
Superconducting qubits are a key contender for quantum computing elements, but they often face challenges like noise and decoherence from two-level systems (TLS). Tantalum (Ta) qubits are notable for their long T coherence times nearing milliseconds, mainly due to fewer TLS, though the cause was unclear. Our research explored this by analyzing the air-oxide interface with density functional theory, particularly comparing Nb oxide (NbO) and Ta oxide (TaO). We discovered that TaO forms a smoother surface with fewer dangling O atoms and TLS than NbO. The greater atomic mass of Ta also lowers the TLS tunnel splittings below the qubit's operating frequency. Furthermore, using external electric fields or SO passivation can significantly reduce TLS on Nb surfaces, potentially improving their coherence times.
References in corpus (27)
- Superconducting Qubits: Current State of Play
- Superconducting Circuits and Quantum Information
- Decoherence in Josephson Qubits from Dielectric Loss
- On-the-fly machine learning force field generation: Application to melting points
- Phase transitions of hybrid perovskites simulated by machine-learning force fields trained on-the-fly with Bayesian inference
- New material platform for superconducting transmon qubits with coherence times exceeding 0.3 milliseconds
- Towards understanding two-level-systems in amorphous solids -- Insights from quantum circuits
- Transmon qubit with relaxation time exceeding 0.5 milliseconds
- Electric field spectroscopy of material defects in transmon qubits
- Systematic Improvements in Transmon Qubit Coherence Enabled by Niobium Surface Encapsulation
- Two-level systems in superconducting quantum devices due to trapped quasiparticles
- Investigation of microwave loss induced by oxide regrowth in high-Q Nb resonators
- Bulk and Surface Tunneling Hydrogen Defects in Alumina
- Projected dipole moments of individual two-level defects extracted using circuit quantum electrodynamics
- Candidate source of flux noise in SQUIDs: adsorbed oxygen molecules
- Polaronic model of Two Level Systems in amorphous solids
- Resolving the positions of defects in superconducting quantum bits
- Path toward manufacturable superconducting qubits with relaxation times exceeding 0.1 ms
- Microscopic Model of Critical Current Noise in Josephson Junctions
- Saturation of Two Level Systems and Charge Noise in Josephson Junction Qubits
- Nitrogen Plasma Passivated Niobium Resonators for Superconducting Quantum Circuits
- Probing defect densities at the edges and inside Josephson junctions of superconducting qubits
- Identification of structural motifs as tunneling two-level systems in amorphous alumina at low temperatures
- Enhancing the Coherence of Superconducting Quantum Bits with Electric Fields
- Why phonon scattering in glasses is universally small at low temperatures
- Hydrogen as a Source of Flux Noise in SQUIDs
- Acceptor-induced bulk dielectric loss in superconducting circuits on silicon