arXiv subjects

H. Douglas Pinckney

Publications and source records attributed to H. Douglas Pinckney.

7 recordsLinked to original sources

arXiv2026

Distinguishing types of correlated errors in superconducting qubits

Errors in superconducting qubits that are correlated in time and space can pose problems for quantum error correction codes. Radiation from cosmic and terrestrial sources can increase the quasiparticle (QP) density in a superconducting qubit device, resulting in an increased rate of QPs tunneling across proximal Josephson junctions (JJs) and causing correlated errors. Mechanical vibrations, such as those induced by the pulse tube (PT) in a dry dilution refrigerator, are also a known source of correlated errors. We measure two types of errors in the same device, linking the first to ionizing radiation and the second to PT operation. We present a method for distinguishing these two types of errors by their temporal, spatial, and frequency domain features, enabling physically motivated error-mitigation strategies. We also present accelerometer data to study the correlation between PT-induced vibrations and the errors. We measure arrays of transmon qubits where the difference in superconducting gap across the JJ is less than the qubit energy, as well as those where the gap is greater than the qubit energy, which has been shown to mitigate radiation-induced errors. The rate of both types of errors is reduced in these latter devices, suggesting that gap engineering is also protective against PT-induced errors.

quant-ph↗

arXiv2026

Characterization of Aluminum Microwave SQUID Multiplexers for CE$ν$NS Detection

We present the design, fabrication, and characterization of an aluminum-based six-channel microwave SQUID multiplexer ($μ$MUX) prototype for transition-edge sensor (TES) readout in the RICOCHET experiment. The device consists of aluminum coplanar-waveguide resonators and RF SQUIDs with Dolan-style Al/AlO$_x$/Al Josephson junctions. By measuring the resonator scattering parameters at a range of probe tone frequencies, powers, and flux bias points, we demonstrate agreement between the device response and existing multiplexer models. We also characterize the noise performance in both open-loop and flux-ramping modes. With a high electron mobility transistor (HEMT) amplifier, open-loop measurements yield a flux sensitivity of 1-1.5 $μΦ_0/\sqrt{Hz}$. With flux-ramp modulation, low-frequency 1/f noise is suppressed, and the flux sensitivity is around 3-4 $μΦ_0/\sqrt{Hz}$, corresponding to a current sensitivity of 24-33 $pA/\sqrt{Hz}$ at the input coil. We further demonstrate a reduction in readout noise by incorporating a Josephson traveling-wave parametric amplifier (JTWPA) between the $μ$MUX and the HEMT. This achieves an open-loop flux sensitivity of 0.3-0.6 $μΦ_0/\sqrt{Hz}$ and an effective system noise temperature below 1 K. These results establish aluminum $μ$MUX devices as a viable and extensible readout technology for low-noise cryogenic detector arrays.

physics.ins-det↗

arXiv2026

Characterization of Radiation-Induced Errors in Superconducting Qubits Protected with Various Gap-Engineering Strategies

Impacts from high-energy particles cause correlated errors in superconducting qubits by increasing the quasiparticle density in the vicinity of the Josephson junctions (JJs). Such errors are particularly harmful as they cannot be easily remedied via conventional error correcting codes. Recent experiments reduced correlated errors by making the difference in superconducting gap energy across the JJ larger than the qubit transition energy. In this work, we assess gap engineering near the JJ ($δΔ_{\mathrm{JJ}}$) and the capacitor/ground-plane ($δΔ_{\mathrm{M1}}$) by exposing arrays of transmon qubits to two sources of radiation. For $α$-particles from an $^{241}$Am source, we observe $T_1$ errors correlated in space and time, supporting a hypothesis that hadronic cosmic rays are a major contributor to the $10^{-10}$ error floor observed in Ref. 1. For electrons from a pulsed linear accelerator, we observe temporally correlated $T_1$ and $T_2$ errors, this measurement is insensitive to spatial correlations. We observe that the severity of correlated $T_1$ errors is reduced for qubit arrays with a greater degree of gap engineering at the JJ. For both $T_1$ and $T_2$ errors, the recovery time is hastened by an increased $δΔ_{\mathrm{M1}}$, which we attribute to the trapping of quasiparticles into the capacitor/ground-plane. We construct a model of quasiparticle dynamics that qualitatively agrees with our observations. This work reinforces the multifaceted influence of radiation on superconducting qubits and provides strategies for improving radiation resilience.

quant-ph↗

arXiv2024

A Stress Induced Source of Phonon Bursts and Quasiparticle Poisoning

The performance of superconducting qubits is degraded by a poorly characterized set of energy sources breaking the Cooper pairs responsible for superconductivity, creating a condition often called ``quasiparticle poisoning". Both superconducting qubits and low threshold dark matter calorimeters have observed excess bursts of quasiparticles or phonons that decrease in rate with time. Here, we show that a silicon crystal glued to its holder exhibits a rate of low-energy phonon events that is more than two orders of magnitude larger than in a functionally identical crystal suspended from its holder in a low-stress state. The excess phonon event rate in the glued crystal decreases with time since cooldown, consistent with a source of phonon bursts which contributes to quasiparticle poisoning in quantum circuits and the low-energy events observed in cryogenic calorimeters. We argue that relaxation of thermally induced stress between the glue and crystal is the source of these events.

physics.ins-det↗

arXiv2024

Synchronous Detection of Cosmic Rays and Correlated Errors in Superconducting Qubit Arrays

Quantum information processing at scale will require sufficiently stable and long-lived qubits, likely enabled by error-correction codes. Several recent superconducting-qubit experiments, however, reported observing intermittent spatiotemporally correlated errors that would be problematic for conventional codes, with ionizing radiation being a likely cause. Here, we directly measured the cosmic-ray contribution to spatiotemporally correlated qubit errors. We accomplished this by synchronously monitoring cosmic-ray detectors and qubit energy-relaxation dynamics of 10 transmon qubits distributed across a 5x5x0.35 mm$^3$ silicon chip. Cosmic rays caused correlated errors at a rate of 1/(10 min), accounting for 17$\pm$1% of all such events. Our qubits responded to essentially all of the cosmic rays and their secondary particles incident on the chip, consistent with the independently measured arrival flux. Moreover, we observed that the landscape of the superconducting gap in proximity to the Josephson junctions dramatically impacts the qubit response to cosmic rays. Given the practical difficulties associated with shielding cosmic rays, our results indicate the importance of radiation hardening -- for example, superconducting gap engineering -- to the realization of robust quantum error correction.

quant-ph↗

arXiv2022

Transition Edge Sensor Chip Design of Modular CEνNS Detector for the Ricochet Experiment

Coherent elastic neutrino-nucleus scattering (CE$ν$NS) offers a valuable approach in searching for physics beyond the Standard Model. The Ricochet experiment aims to perform a precision measurement of the CE$ν$NS spectrum at the Institut Laue-Langevin (ILL) nuclear reactor with cryogenic solid-state detectors. The experiment will employ an array of cryogenic thermal detectors, each with a mass of around 30 g and an energy threshold of 50 eV. One section of this array will contain 9 Transition Edge Sensor (TES) based calorimeters. The design will not only fulfill requirements for Ricochet, but also act as a demonstrator for future neutrino experiments that will require thousands of macroscopic detectors. In this article we present an updated TES chip design as well as performance predictions based on a numerical modeling.

physics.ins-det↗

arXiv2020

Single Electron-Hole Pair Sensitive Silicon Detector with Surface Event Rejection

We demonstrate single electron-hole pair resolution in a single-sided, contact-free 1 cm$^2$ by 1 mm thick Si crystal operated at 48 mK, with a baseline energy resolution of 3 eV. This crystal can be operated at voltages in excess of $\pm50$ V, resulting in a measured charge resolution of 0.06 electron-hole pairs. The high aluminum coverage ($\sim$70%) of this device allows for the discrimination of surface events and separation of events occurring near the center of the detector from those near the edge. We use this discrimination ability to show that non-quantized dark events seen in previous detectors of a similar design are likely dominated by charge leakage along the side wall of the device.

physics.ins-det↗