Radiation Impact on Superconducting Qubits (RISQ 2024)

Session

Poster Session

Not scheduled

2nd Floor Crossover (Wiilson Hall)

Contribution list Timetable

42. Applications of Strain Sensing for Superconducting Qubit Devices

Optomechanical strain sensing provides attractive opportunities for studying stress-induced (i.e. non-radiogenic) phonon bursts, which have been demonstrated to limit the coherence times and minimum charge jump rates of superconducting qubits [1,2,3]. We are investigating SiN microring optical resonator strain sensors, developed at Purdue University [4], for applications in QIS and fundamental...

2. Controllably irradiating superconducting qubits with gamma rays to characterize quasiparticle poisoning

High-energy radiation, such as gamma rays or muons, poses a threat to the use of superconducting qubit arrays to create a fault-tolerant quantum computer. When such radiation impacts a superconducting qubit chip, many electron-hole pairs and energetic phonons are produced. The electrons and holes can travel some distance and affect the charge environment for the qubits nearby. However, the...

10. Creating Correlated Errors on Transmon Qubits Using an Electron Linear Accelerator

Superconducting transmon qubits are known to be susceptible to errors due to ionizing radiation from ambient radioactive decay and cosmic ray sources (muons). Here, we use a ~22 MeV electron linear accelerator (linac) as an on-demand high-energy particle source to study deleterious effects on a multi-qubit transmon system. The linac provides a pulsed, microsecond burst of radiation that can be...

12. Development of qubit-based light dark matter detector on sapphire substrate

One of the challenges in exploring target materials for dark matter searches is the detection of sub-eV energy excitations from light dark matter interaction with a target material. Dark matter interaction can excite sub-eV optical phonon modes in polar materials like sapphire. Furthermore, the anisotropy of sapphire crystal could provide a signature of daily modulation of the dark matter...

41. Disentangling the sources of ionizing radiation in superconducting qubits

Radioactivity was recently discovered as a source of decoherence and correlated errors for the real-world imple- mentation of superconducting quantum processors. In this work, we measure levels of radioactivity present in a typical laboratory environment (from muons, neutrons, and γ -rays emitted by naturally occurring radioactive isotopes) and in the most commonly used materials for the...

47. Estimating the Energy Threshold of Qubit-based Detectors in a Relaxation Sensing Scheme

Over the last decade, several low-energy physics searches, including the hunt for particle dark matter, have driven interest in developing increasingly sensitive particle detectors. Superconducting quantum sensors based on Cooper Pairs provide a possible channel for sensing O(meV) energy depositions, and therefore could represent a significant step in developing such low-threshold detectors....

8. eV-scale Modelling of Low-Energy Backgrounds in Superconducting Tunnel Junctions utilizing GEANT4 and G4CMP

The BeEST experiment searches for physics beyond the standard model (BSM) in the neutrino sector by utilizing the electron capture (EC) decay of 7Be. The 7Be is embedded in superconducting tunnel junction (STJ) sensors such that the low-energy (eV-scale) radiation is detected with high energy resolution and efficiency. Modelling of low-energy backgrounds is crucial to understanding potential...

44. First Measurement of Correlated Charge Noise in Superconducting Qubits at an Underground Facility

Recent work indicates that non-equilibrium quasiparticles can contribute to decoherence effects in superconducting qubits. Ionizing radiation, for example, has been shown to create errors in qubit arrays that are correlated in both space and time. For quantum computing, such correlated errors create problems for standard error-correcting codes. For quantum sensing, these same phenomena can...

46. Incorporating Phonon Kinematics of Novel Materials in G4CMP to Study Qubit Chip Response to Energy Deposits

The Geant4 Condensed Matter Physics (G4CMP) toolkit was designed to simulate the transport of charge and phonons in detectors made of Silicon and Germanium. Through these simulations, the toolkit effectively reproduces phenomena such as heat-pulse propagation times, average charge-carrier drift velocities, and phonon caustics. However, its limitation to Silicon and Germanium restricts its...

4. Investigation of coherence of niobium-based resonators enabled by a fast-sealing microwave cavity

We present our recent work exploring the coherence of niobium-based superconducting devices, with a focus on two aspects. The first aspect is the role of the niobium and substrate surfaces. We use an approach for sample packaging where devices can be quickly isolated in vacuum after metal oxide removal, using a special purpose sealable microwave cavity. The second aspect is the role of film...

5. Low Tc Hafnium Kinetic Inductance Device for Dark Matter Search

Closely related but contrary to Qubits, dark matter detectors are built to be ultra-sensitive to phonons created from impacts in the substrate. TESs have been successfully implemented as phonon sensors on gram-scale detectors. Kinetic inductance devices (KIDs) are naturally suitable for multiplexing readout, which can scale detectors to kilogram scale.
At LBL we focus on low Tc Hafnium KIDs...

3. Optimal Experimental Design for Quantum Circuits: A case study for the mitigation of quasiparticle poisoning

Superconducting circuits are the most widely used system for quantum computing, and many of the key accomplishments in this field have been performed using superconducting-based quantum processors. The improvement of device performance through the mitigation and control of qubit errors is currently a critical step for executing complex quantum algorithms. However, the experimental routines...

7. Quantum Opportunities at the Sanford Underground Research Facility

The Sanford Underground Research Facility (SURF) has been operating for 17 years as an international facility dedicated to advancing compelling multidisciplinary underground scientific research in rare-process physics, as well as offering research opportunities in other disciplines. SURF laboratory facilities include a Surface Campus as well as access to different elevations down to the...

6. Quasiparticle Posioning, the Low Energy Excess and Stress Relaxation

Both superconducting qubits and low threshold calorimeters see unexpected bursts of energy in their superconductors which decrease in rate after cooldown, often called the "Low Energy Excess" (LEE) in calorimeters and associated with the "Quasiparticle Poisoning" problem in superconducting qubits. I will discuss the evidence linking these two phenomona, and show that the relaxation of glue on...

45. Simulation Framework for Non-equilibrium Mode-resolved Phonon-mediated Quasiparticle Poisoning in Superconducting Qubits

Superconducting qubits are susceptible to non-equilibrium phonon excitations which incite chip-wide quasiparticle burst events responsible for the energy relaxation and dephasing of the qubit states. In this work, we demonstrate a phonon-mode resolved simulation framework governed by ab initio data (force constants, phonon lifetimes, electron-phonon coupling matrix, etc.) to describe...

11. Spectroscopic measurements and models of energy deposition in the substrate of quantum circuits by natural ionizing radiation

Naturally occurring background radiation is a potential source of correlated decoherence events in superconducting qubits that will challenge error-correction schemes. To characterize the radiation environment in an unshielded laboratory, we performed broadband, spectroscopic measurements of background events in silicon substrates located inside a millikelvin refrigerator, an environment...

48. Study of Two-Level System Defects in Transmon Qubits

A major source of decoherence in superconducting qubits is believed to be due to defects that manifest as two-level systems (TLS) present in qubit materials. In this work, we have investigated TLS defects in planar transmon qubits. We probed TLS defects in our qubits spectroscopically by utilizing microwave pulse sequences that shift the qubit g-e transition into resonance with the defects. We...

1. Superconducting qubit dephasing correlated with radiating events

A major issue currently impeding qubit error-correction is spatially correlated qubit decoherence which is likely caused by cosmic radiation. Superconducting microwave kinetic inductance detectors (MKIDs) are a promising candidate for detection of these events due to their sensitivity to phonon bursts in a substrate. We surrounded a qubit sample with two, three by three arrays of MKIDs which...

9. Superconducting Qubits as Quantum Sensors for the Detection of Ionizing Radiation

We present measurements directed toward utilizing a superconducting qubit, not for quantum information processing, but as a quantum sensor for the detection of ionizing radiation. Whereas ionizing radiation presents a potentially serious problem for quantum error correction due to spatially and temporally correlated errors, it represents an opportunity for quantum sensing. A parameter...

43. Ta Based Damascene Resonators

The latest performance improvement in superconducting transmon qubits is associated to changes in materials and surface engineering. These approaches yield coherence time up to 0.5 milliseconds for Ta based devices, with Nb-based qubits following closely. This improvement is attributed to the oxidation state of Ta vs Nb, which effect the Two-Level-System (TLS) noise in associated devices. As...