Mitigating losses of superconducting qubits strongly coupled to defect modes

Physical Review Applied, Journal Year: 2025, Volume and Issue: 23(4)

Published: April 24, 2025

Language: Английский

---

Mitigation of oxide growth on aluminum thin films: The role of self-assembled monolayers in superconducting quantum circuits

AVS Quantum Science, Journal Year: 2025, Volume and Issue: 7(2)

Published: May 14, 2025

The native oxide layer formed on aluminum (Al) surfaces in superconducting quantum circuits is a significant source of two-level system defects, which couple with electric fields and degrade coherence. Recent research has explored etching, encapsulation, other surface treatments as potential strategies to mitigate the formation oxides at air interfaces these circuits. This study demonstrates novel approach passivate Al–air interface using molecular self-assembled monolayer (SAM). Freshly prepared Al thin films were passivated SAMs by immersing Al-coated silicon substrates SAM solutions. X-ray photoelectron spectroscopy (XPS) confirms successful binding absence further growth. Moreover, passivation remains stable after aging for 15 days ambient conditions, evidenced XPS contact angle measurements. Scanning electron microscopy analyses support mitigation These findings suggest that SAM-based offers promising method reducing microwave loss improving performance Al-based

Language: Английский

---

Characterization of Microwave Loss Using Multimode Superconducting Resonators

Physical Review Applied, Journal Year: 2023, Volume and Issue: 20(2)

Published: Aug. 18, 2023

Understanding the loss mechanisms in materials is crucial to improving coherence superconducting quantum circuits. The authors present a technique based on multimode resonators that distinguishes and quantifies all channels relevant materials. Applying this reveals both chemical etching diamond turning reduce surface losses high-purity aluminum, while coating diamond-turned surfaces with thin-film aluminum significantly improves joint quality. This method can be used design on-chip devices characterize microwave losses, as well quantify effects of fabrication processes.

Language: Английский

---

Characterization of process-related interfacial dielectric loss in aluminum-on-silicon by resonator microwave measurements, materials analysis, and imaging

Deleted Journal, Journal Year: 2024, Volume and Issue: 1(2)

Published: June 1, 2024

We systematically investigate the influence of fabrication process on dielectric loss in aluminum-on-silicon superconducting coplanar waveguide resonators with internal quality factors (Qi) about one million at single-photon level. These devices are essential components quantum processors; they also serve as proxies for understanding energy qubits. By varying several steps, we identify relative importance reducing substrate–metal and substrate–air interfaces. find that it is to clean silicon substrate hydrogen fluoride (HF) prior aluminum deposition. A post-fabrication removal oxides surface film by immersion HF further improves Qi. observe a small, but noticeable, adverse effect omitting either standard cleaning (SC1), pre-deposition heating 300 °C, or situ post-deposition oxidation film’s top surface. no improvement due excessive pumping meant reach background pressure below 6 × 10−8 mbar. correlate measured microscopic properties interface through characterization x-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, transmission electron microscopy, energy-dispersive atomic force microscopy.

Language: Английский

---

Exploring the relationship between deposition method, microstructure, and performance of Nb/Si-based superconducting coplanar waveguide resonators

Acta Materialia, Journal Year: 2024, Volume and Issue: 276, P. 120153 - 120153

Published: July 4, 2024

Superconducting quantum circuits (SQC) are one of the most promising hardware platforms for computing, yet their performance is currently limited by presence various structural defects inside circuit's structure. Despite impressive progress in past decade, a precise understanding origin these from fabrication processes and impact on coherence still lacking. In this study, we performed comprehensive investigation microstructure, superconductivity, resonator quality factor Nb films deposited high-power impulse magnetron sputtering (HiPIMS) direct current (DC) sputtering. A suite characterization techniques, including electron microscopy with spectroscopy, secondary ion mass spectrometry, magneto-optical microscopy, pump-probe reflectivity spectroscopy used. We reveal that niobium (Nb) resonators fabricated using HiPIMS exhibit smaller average grain size, thicker surface oxide larger thickness variations (rougher surface), amorphous Nb/Si interface layer compared to samples DC identified oxides (mainly located at along boundaries) Nb-Si layers (at interface) major potential sources two-level system (TLS), while off-stochiometric suboxides close surface, crystalline (i.e., dislocations boundary, point introduced during deposition) main contributors non-TLS sources. Our findings clarify relationship between different loss mechanisms, highlighting importance material microstructure control optimization SQC.

Language: Английский

---