Publications (42)
Discovery of Nb hydride precipitates in superconducting qubits
Jaeyel Lee, Zuhawn Sung, Akshay A. Murthy +3
We report the first evidence of the formation of niobium hydrides within niobium films on silicon substrates in superconducting qubits fabricated at Rigetti Computing. We combine c…
Ultracoherent superconducting cavity-based multiqudit platform with error-resilient control
Taeyoon Kim, Tanay Roy, Xinyuan You +26
Realizing the promise of quantum computing requires simultaneously increasing Hilbert-space size and coherence times. While qubit-based architectures have long been the dominant pa…
Stabilizing and improving qubit coherence by engineering noise spectrum of two-level systems
Xinyuan You, Ziwen Huang, Ugur Alyanak +3
Superconducting circuits are a leading platform for quantum computing. However, their coherence times are still limited and exhibit temporal fluctuations. Those phenomena are often…
High-efficiency microwave-optical quantum transduction based on a cavity electro-optic superconducting system with long coherence time
Changqing Wang, Ivan Gonin, Anna Grassellino +4
Frequency conversion between microwave and optical photons is a key enabling technology to create links between superconducting quantum processors and to realize distributed quantu…
Two-Level System Spectroscopy from Correlated Multilevel Relaxation in Superconducting Qubits
Tanay Roy, Xinyuan You, David van Zanten +5
Transmon qubits are a cornerstone of modern superconducting quantum computing platforms. Temporal fluctuations of energy relaxation in these qubits are widely attributed to microsc…
Identifying Materials-Level Sources of Performance Variation in Superconducting Transmon Qubits
Akshay A. Murthy, Mustafa Bal, Michael J. Bedzyk +46
The Superconducting Materials and Systems (SQMS) Center, a DOE National Quantum Information Science Research Center, has conducted a comprehensive and coordinated study using super…
Measurement of the Low-temperature Loss Tangent of High-resistivity Silicon with a High Q-factor Superconducting Resonator
Mattia Checchin, Daniil Frolov, Andrei Lunin +2
In this letter, we present the direct loss tangent measurement of a high-resistivity intrinsic (100) silicon wafer in the temperature range from ~ 70 mK to 1 K, approaching the qua…
Squeezing enhanced sensing at an exceptional point
Changqing Wang, Deyuan Hu, Silvia Zorzetti +3
Pushing the boundaries of measurement precision is central for sensing and metrology, pursued by nonclassical resources such as squeezing, and non-Hermitian degeneracies with disti…
Two-tooth bosonic quantum comb for temporal-correlation sensing
Shaojiang Zhu, Xinyuan You, Alexander Romanenko +1
We introduce a two-tooth bosonic quantum comb that captures the sequential interactions between a thermal absorber and a long-lived coherent probe. The comb provides a causal, mult…
Vortex-Controlled Quasiparticle Multiplication and Self-Growth Dynamics in Superconducting Resonators
Joong M. Park, Martin Mootz, Richard H. J. Kim +11
Even in the quantum limit, non-equilibrium quasiparticle (QP) populations induce QP poisoning that irreversibly relaxes the quantum state and significantly degrades the coherence o…
Analysis of RF Surface Loss in a Planar 2D Qubit
Andrei Lunin, Mustafa Bal, Akshay Murthy +3
The Josephson junction and shunt capacitor form a transmon qubit, which is the cornerstone of modern quantum computing platforms. For reliable quantum computing, it is important ho…
Oxygen Vacancies in Niobium Pentoxide as a Source of Two-Level System Losses in Superconducting Niobium
Daniel Bafia, Akshay Murthy, Anna Grassellino +1
We identify a major source of quantum decoherence in three-dimensional superconducting radio-frequency (SRF) resonators and two-dimensional transmon qubits composed of oxidized nio…
Coherence-Mediated Quantum Thermometry in a Hybrid Circuit-QED Architecture
Shaojiang Zhu, Xinyuan You, Alexander Romanenko +1
Quantum thermometry plays a critical role in the development of low-temperature sensors and quantum information platforms. In this work, we propose and theoretically analyze a hybr…
Effect of metal encapsulation on bulk superconducting properties of niobium thin films used in qubits
Amlan Datta, Kamal R. Joshi, Sunil Ghimire +18
Niobium metal occupies nearly 100\% of the volume of a typical 2D transmon device. While the aluminum Josephson junction is of utmost importance, maintaining quantum coherence acro…
Overlap junctions for superconducting quantum electronics and amplifiers
Mustafa Bal, Junling Long, Ruichen Zhao +10
Due to their unique properties as lossless, nonlinear circuit elements, Josephson junctions lie at the heart of superconducting quantum information processing. Previously, we demon…
High-Order Qubit Dephasing at Sweet Spots by Non-Gaussian Fluctuators: Symmetry Breaking and Floquet Protection
Ziwen Huang, Xinyuan You, Ugur Alyanak +3
Although the Gaussian-noise assumption is widely adopted in the study of qubit decoherence, non-Gaussian noise sources, especially the strong discrete fluctuators, have been detect…
Quantum Sensing for High Energy Physics
Zeeshan Ahmed, Yuri Alexeev, Giorgio Apollinari +113
Report of the first workshop to identify approaches and techniques in the domain of quantum sensing that can be utilized by future High Energy Physics applications to further the s…
Model for Diffusion-Induced Ramsey Narrowing
Alexander Romanenko, Leonid Yatsenko
Diffusion-induced Ramsey narrowing that appears when atoms can leave the interaction region and repeatedly return without lost of coherence is investigated using strong collisions…
Demonstrating magnetic field robustness and reducing temporal T1 noise in transmon qubits through magnetic field engineering
Bektur Abdisatarov, Tanay Roy, Daniel Bafia +10
The coherence of superconducting transmon qubits is often disrupted by fluctuations in the energy relaxation time (T1), limiting their performance for quantum computing. While back…
Evaluating radiation impact on transmon qubits in above and underground facilities
Francesco De Dominicis, Tanay Roy, Ambra Mariani +20
Superconducting qubits can be sensitive to abrupt energy deposits caused by cosmic rays and ambient radioactivity. While previous studies have explored correlated effects in time a…
Crosstalk-Robust Quantum Control in Multimode Bosonic Systems
Xinyuan You, Yunwei Lu, Taeyoon Kim +10
High-coherence superconducting cavities offer a hardware-efficient platform for quantum information processing. To achieve universal operations of these bosonic modes, the requisit…
Frequency dependence of trapped flux sensitivity in SRF cavities
Mattia Checchin, Martina Martinello, Anna Grassellino +6
In this letter, we present the frequency dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treat…
Enhanced Superconducting Qubit Performance Through Ammonium Fluoride Etch
Cameron J. Kopas, Dominic P. Goronzy, Thang Pham +19
The performance of superconducting qubits is often limited by dissipation and two-level systems (TLS) losses. The dominant sources of these losses are believed to originate from am…
Systematic Improvements in Transmon Qubit Coherence Enabled by Niobium Surface Encapsulation
Mustafa Bal, Akshay A. Murthy, Shaojiang Zhu +37
We present a novel transmon qubit fabrication technique that yields systematic improvements in T relaxation times. We fabricate devices using an encapsulation strategy that inv…
Discovery of Niobium Hydride Precipitates in Superconducting Qubits
Zuhawn Sung, Daniel Bafia, Arely Cano +6
We report the evidence of the formation of niobium hydride phase within niobium films on silicon substrates in superconducting qubits fabricated at Rigetti Computing. For this stud…
Fast ZZ-Free Entangling Gates for Superconducting Qubits Assisted by a Driven Resonator
Ziwen Huang, Taeyoon Kim, Tanay Roy +4
Engineering high-fidelity two-qubit gates is an indispensable step toward practical quantum computing. For superconducting quantum platforms, one important setback is the stray int…
Loss tangent fluctuations due to two-level systems in superconducting microwave resonators
André Vallières, Megan E. Russell, Xinyuan You +10
Superconducting microwave resonators are critical to quantum computing and sensing technologies. Additionally, they are common proxies for superconducting qubits when determining t…
Quasiparticle spectroscopy in technologically-relevant niobium using London penetration depth measurements
Sunil Ghimire, Kamal R. Joshi, Amlan Datta +10
London penetration depth was measured in niobium foils, thin films, single crystals, and superconducting radio-frequency (SRF) cavity pieces cut out from different places. The low-…
Completely Positive Map for Noisy Driven Quantum Systems Derived by Keldysh Expansion
Ziwen Huang, Yunwei Lu, Anna Grassellino +3
Accurate modeling of decoherence errors in quantum processors is crucial for analyzing and improving gate fidelities. To increase the accuracy beyond that of the Lindblad dynamical…
Selective thermal evolution of native oxide layer in Nb and Nb3Sn-coated SRF grade Nb: An in-situ angular XPS study
Arely Cano, Grigory V. Eremeev, Juan R. Zuazo +5
This contribution discusses the results of an in-situ angular XPS study on the thermal evolution of the native oxide layer on Nb3Sn and pure Nb. XPS data were recorded with convent…
TOF-SIMS Analysis of Decoherence Sources in Nb Superconducting Resonators
Akshay A. Murthy, Jae-Yel Lee, Cameron Kopas +6
Superconducting qubits have emerged as a potentially foundational platform technology for addressing complex computational problems deemed intractable with classical computing. Des…
Internal Friction Measures to Study Precipitates Formation in EP and N-Doped Bulk Nb for SRF Applications
Tiziana Spina, Anna Grassellino, Alexander Romanenko
Main focus of this study is the investigation of thermodynamics phenomena responsible for the High Field Q Slope (HFQS) in SRF cavities by Internal Friction (IF) measurement. Mecha…
Millikelvin measurements of permittivity and loss tangent of lithium niobate
Silvia Zorzetti, Changqing Wang, Ivan Gonin +5
Lithium Niobate is an electro-optic material with many applications in microwave signal processing, communication, quantum sensing, and quantum computing. In this letter, we presen…
Quantum computing hardware for HEP algorithms and sensing
M. Sohaib Alam, Sergey Belomestnykh, Nicholas Bornman +37
Quantum information science harnesses the principles of quantum mechanics to realize computational algorithms with complexities vastly intractable by current computer platforms. Ty…
Floquet-engineered fast SNAP gates in weakly coupled circuit-QED systems
Xinyuan You, Andy C. Y. Li, Tanay Roy +5
Superconducting cavities with high quality factors, coupled to a fixed-frequency transmon, provide a state-of-the-art platform for quantum information storage and manipulation. The…
Developing a Chemical and Structural Understanding of the Surface Oxide in a Niobium Superconducting Qubit
Akshay A. Murthy, Paul Masih Das, Stephanie M. Ribet +11
Superconducting thin films of niobium have been extensively employed in transmon qubit architectures. Although these architectures have demonstrated remarkable improvements in rece…
Nitrogen-Doped 9-Cell Cavity Performance in a Test Cryomodule for LCLS-II
Dan Gonnella, Ralf Eichhorn, Fumio Furuta +13
The superconducting RF linac for LCLS-II calls for 1.3 GHz 9-cell cavities with an average intrinsic quality factor Q0 of 2.7x10^10 at 2 K and 16 MV/m accelerating gradient. Two ni…
Improved Dark Photon Sensitivity from the Dark SRF Experiment
Saarik Kalia, Zhen Liu, Bianca Giaccone +15
We report the refined dark-photon exclusion bound from Dark SRF's pathfinder run. Our new result is driven by improved theoretical modeling of frequency instability in high-quality…
Deepest sensitivity to wavelike dark photon dark matter with superconducting radio frequency cavities
Raphael Cervantes, Jose Aumentado, Caterina Braggio +9
Wavelike, bosonic dark matter candidates like axions and dark photons can be detected using microwave cavities known as haloscopes. Traditionally, haloscopes consist of tunable cop…
Disentangling the Impact of Quasiparticles and Two-Level Systems on the Statistics of Superconducting Qubit Lifetime
Shaojiang Zhu, Xinyuan You, Ugur Alyanak +8
Temporal fluctuations in the superconducting qubit lifetime, , bring up additional challenges in building a fault-tolerant quantum computer. While the exact mechanisms remain…
First Direct Observation of Nanometer size Hydride Precipitations on Superconducting Niobium
Zu Hawn Sung, Arely Cano, Akshay Murthy +5
Superconducting niobium serves as a key enabling material for superconducting radio frequency (SRF) technology as well as quantum computing devices. At room temperature, hydrogen c…
Phase-controlled improvement of photon lifetime in coupled superconducting cavities
Changqing Wang, Oleksandr S Melnychuk, Crispin Contreras-Martinez +9
High-quality cavities are crucial for various fundamental physical studies and applications. Here we find that by coupling two cavities directly or via a phase-tunable coupling cha…