Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation

npj Quantum Information, Journal Year: 2024, Volume and Issue: 10(1)

Published: April 26, 2024

Language: Английский

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Surpassing millisecond coherence in on chip superconducting quantum memories by optimizing materials and circuit design

Nature Communications, Journal Year: 2024, Volume and Issue: 15(1)

Published: May 1, 2024

The performance of superconducting quantum circuits for computing has advanced tremendously in recent decades; however, a comprehensive understanding relaxation mechanisms does not yet exist. In this work, we utilize multimode approach to characterizing energy losses circuits, with the goals predicting device and improving coherence through materials, process, circuit design optimization. Using approach, measure significant reductions surface bulk dielectric by employing tantalum-based materials platform annealed sapphire substrates. With knowledge predict times aluminum- transmon qubits, find that they are consistent experimental results. We additionally optimize geometry maximize within coaxial tunnel architecture, realize on-chip memories single-photon Ramsey 2.0 - 2.7 ms, limited their 1.0 1.4 ms. These results demonstrate an advancement towards more modular compact architecture bosonic qubits reproducibly high coherence.

Language: Английский

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Improved coherence in optically defined niobium trilayer-junction qubits

Physical Review Applied, Journal Year: 2024, Volume and Issue: 21(2)

Published: Feb. 23, 2024

Niobium offers the benefit of increased operating temperatures and frequencies for Josephson junctions, which are core component superconducting devices. However existing niobium processes limited by more complicated fabrication methods higher losses than now-standard aluminum junctions. Combining recent trilayer advancements, to remove lossy dielectrics modern qubit design, we revisit junctions fabricate all-niobium transmons using only optical lithography. We characterize devices in microwave domain, measuring coherence times up $62~\mu$s an average quality factor above $10^5$: much closer state-of-the-art aluminum-junction find gap energy also results reduced quasiparticle sensitivity $0.16~$K, where junction performance deteriorates. Our process is readily applied standard optical-based foundry processes, opening new avenues direct integration scalability, paves way higher-temperature higher-frequency quantum

Language: Английский

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Fano Interference in Microwave Resonator Measurements

Physical Review Applied, Journal Year: 2023, Volume and Issue: 20(1)

Published: July 26, 2023

Resonator measurements are a simple but powerful tool to characterize material's microwave response. The losses of resonant mode quantified by its internal quality factor ${Q}_{\mathrm{i}}$, which can be extracted from the scattering coefficient in reflection or transmission measurement. Here we show that systematic error on ${Q}_{\mathrm{i}}$ arises Fano interference signal with background path. Limited knowledge interfering paths given setup translates into range uncertainty for increases coupling coefficient. We experimentally illustrate relevance typical resonator and associated pitfalls encountered extracting ${Q}_{\mathrm{i}}$. On other hand, also how utilize eliminate error.

Language: Английский

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Advanced quantum mechanics

Oxford University Press eBooks, Journal Year: 2023, Volume and Issue: unknown, P. 674 - 678

Published: Aug. 25, 2023

Subject Astronomy and Astrophysics Computational Physics Collection: Oxford Scholarship Online

Language: Английский

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Mitigation of frequency collisions in superconducting quantum processors

Physical Review Research, Journal Year: 2023, Volume and Issue: 5(4)

Published: Oct. 2, 2023

The reproducibility of qubit parameters is a challenge for scaling up superconducting quantum processors. Signal cross talk imposes constraints on the frequency separation between neighboring qubits. uncertainty transmon qubits arising from fabrication process attributed to deviations in Josephson junction area, tunnel barrier thickness, and shunt capacitor. We decrease sensitivity these variations by fabricating larger junctions reduce wafer-level standard deviation resistance down 2%. characterize 32 identical demonstrate frequencies with 40 MHz (i.e., 1%) quality factors exceeding 2 million. perform two-level-system (TLS) spectroscopy observe no significant increase number TLSs causing relaxation. further show simulation that our parametric-gate architecture, accounting only errors caused frequency, we can scale 100 an average three collisions quantum-gate transition frequencies, assuming $2%$ $99.9%$ target gate fidelity.

Language: Английский

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Tuning microwave losses in superconducting resonators

Superconductor Science and Technology, Journal Year: 2023, Volume and Issue: 36(6), P. 063002 - 063002

Published: March 7, 2023

Performance of superconducting resonators, particularly cavities for particle accelerators and micro thin film resonators quantum computations photon detectors has been improved substantially by recent materials treatments technological advances. As a result, the niobium have reached quality factors $Q\sim 10^{11}$ at 1-2 GHz 1.5 K breakdown radio-frequency (rf) fields $H$ close to dc superheating field Meissner state. These advances raise question whether state-of-the-art are fundamental limits, what these limits actually are, extent $Q$ can be pushed nano structuring impurity management. issues also relevant many applications using high-Q including single-photon circuits. This topical review outlines basic physical mechanisms rf nonlinear surface impedance controlled quasiparticles, dielectric losses trapped vortices, as well dynamic limit Sections cover ways engineering an optimum quasiparticle density states superfluid reduce kinetic inductance pairbreaking related magnetic impurities, currents, proximity-coupled metallic layers surface. A section focuses on residual resistance which dominates ultra low temperatures. Microwave vortices their reduction optimizing concentration impurities pinning potential discussed.

Language: Английский

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Structure and Formation Mechanisms in Tantalum and Niobium Oxides in Superconducting Quantum Circuits

ACS Nano, Journal Year: 2024, Volume and Issue: unknown

Published: July 21, 2024

Improving the qubit's lifetime (T1) is crucial for fault-tolerant quantum computing. Recent advancements have shown that replacing niobium (Nb) with tantalum (Ta) as base metal significantly increases T1, likely due to a less lossy native surface oxide. However, understanding formation mechanism and nature of both oxides still limited. Using aberration-corrected transmission electron microscopy energy loss spectroscopy, we found Ta oxide has fewer suboxides than Nb We observed an abrupt oxidation state transition from Ta2O5 Ta, opposed gradual shift Nb2O5, NbO2, NbO Nb, consistent thermodynamic modeling. Additionally, amorphous exhibits closer-to-crystalline bonding potentially hindering H atomic diffusion toward oxide/metal interface. Finally, propose arising between two states within distorted octahedron in structure, causing two-level system loss. Our findings offer deeper differences oxides, providing valuable insights advancing superconducting qubits through engineering.

Language: Английский

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Formation and Microwave Losses of Hydrides in Superconducting Niobium Thin Films Resulting from Fluoride Chemical Processing

Advanced Functional Materials, Journal Year: 2024, Volume and Issue: 34(36)

Published: April 10, 2024

Superconducting Nb thin films have recently attracted significant attention due to their utility for quantum information technologies. In the processing of films, fluoride-based chemical etchants are commonly used remove surface oxides that known affect superconducting devices adversely. However, these same can also introduce hydrogen form hydrides, potentially negatively impacting microwave loss performance. Here, we present comprehensive materials characterization hydrides formed in as a function fluoride treatments. particular, secondary-ion mass spectrometry, X-ray scattering, and transmission electron microscopy reveal spatial distribution phase transformation hydrides. The rate hydride formation is determined by solution acidity etch Nb2O5, which acts diffusion barrier into Nb. resulting detrimental properties lead increased power-independent coplanar waveguide resonators. do not correlate with two-level system or device aging mechanisms. Overall, this work provides insight role loss, thus guiding ongoing efforts maximize coherence time devices.

Language: Английский

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Microwave characterization of tantalum superconducting resonators on silicon substrate with niobium buffer layer

APL Materials, Journal Year: 2024, Volume and Issue: 12(2)

Published: Feb. 1, 2024

Tantalum thin films sputtered on unheated silicon substrates are characterized with microwaves at around 10 GHz in a mK environment. We show that the phase of tantalum body-centered cubic lattice (α-Ta) can be grown selectively by depositing niobium buffer layer prior to film. The physical properties films, such as superconducting transition temperature and crystallinity, change markedly addition layer. Coplanar waveguide resonators based composite film exhibit significantly enhanced internal quality factors compared without factor approaches 2 × 107 large-photon-number limit. While decreases single-photon level owing two-level system (TLS) loss, we have deduced one causes TLS loss is amorphous film–substrate interface, which originates from substrate cleaning before deposition rather than itself. dependence shows marked rise below 200 mK, suggesting presence TLS–TLS interactions. present low-loss deposited heating thus various potential applications quantum electronics.

Language: Английский

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