Understanding energy transport in low-temperature detectors is essential for rare-event searches, quantum sensing applications, and studies of radiation-induced effects in matter. In this work, we extend the G4CMP framework to describe charge transport in sapphire, motivated by applications in dark matter searches and cryogenic radiation detection. For sapphire, a material of growing interest...
One of the roadblocks towards the implementation of a fault-tolerant superconducting quantum processor is impacts of ionizing radiation with the qubit substrate. Such impacts temporarily elevate the density of quasiparticles (QPs) across the device, leading to correlated qubit error bursts. The most damaging errors—T1 errors—stem from QP tunneling across the qubit Josephson junctions (JJs)....
We will discuss devices that have microwave kinetic inductance detectors (MKIDs) fabricated on the same substrate as qubits to assessing the impact of ionizing radiation. We will present our results using the MKIDs as a radiation sensor to look for correlations between detected events and two-level system dynamics: we observe no correlation in our data. We will also compare the recovery time...
Ionizing radiation impacts create bursts of quasiparticle density in superconducting qubits. These bursts temporarily degrade qubit coherence, which can be detrimental for quantum error correction. Here, we experimentally resolve quasiparticle bursts in 3D gap-engineered transmon qubits by continuously monitoring qubit transitions. Gap engineering allows us to reduce the burst detection rate...
Spatiotemporally correlated error bursts, arising from quasiparticles generated by ionizing radiation and mechanical noise, pose significant challenges to implementing quantum error correction in superconducting quantum processors. In this work, we explore methods for detecting these errors in two superconducting circuits: offset charge sensitive (OCS) transmons and Fluxonium. In OCS...
In addition to radiation impacts, superconducting qubit arrays can be subject to correlated quasiparticle poisoning from nonionizing sources that also result in bursts of pair-breaking phonons. We observe elevated correlated and single-qubit poisoning rates in superconducting qubit arrays at the start of a cooldown followed by power-law reductions in time, while the rate of offset charge...
In the last decade, the sensitivity of superconducting athermal phonon detectors has improved by nearly two orders of magnitude, driven largely by the scientific need to search for dark matter with smaller masses and thus smaller energy depositions. Though these detectors are fabricated using nearly identical materials and fabrication techniques as those used for superconducting qubits, they...
We investigate qubit error bursts in 5- and 7-transmon processors of similar design, fabrication and packaging, but with different types of qubit Josephson junctions. The duration and rate of bursts are device specific but within the range of prior experiments and consistent with ionizing radiation. We observe two unforeseen signatures specifically in the processor with Dolan junctions. First,...
The QUAntum LImited PHotons In the Dark Experiment (QUALIPHIDE) is a cryogenic broadband search for light dark matter candidates, primarily looking for signatures of massive hidden photons kinetically mixing with Standard Model photons. We report results from an experimental campaign coupling a focusing metallic dish to a pixelated array of energy-resolving $\sim$3 to $\sim$120THz sensitive...
We evaluate the quasiparticle contribution to the frequency shift and relaxation rates of a transmon with the Josephson junctions connecting superconductors that have unequal energy gaps. The gap difference substantially affects the transmon characteristics. We investigate their dependence on the density and effective temperature of the quasiparticles, and on the nominal (unperturbed by the...
Quantum error correction fundamentally requires that physical errors are sufficiently uncorrelated in time and space. In superconducting qubit processors, impacts from ionizing radiation violate this assumption by elevating quasiparticle density across the substrate, triggering correlated qubit error bursts. Previously, we demonstrated that the most damaging of these—correlated T1 errors...
The CLIQUE (Controlled Linac Irradiation of Quantum Experiments) Facility at Johns Hopkins Applied Physics Laboratory is an experimental user facility that contains an electron linear accelerator (linac) used as an on-demand high-energy particle source to study deleterious effects on quantum systems. The linac provides a pulsed, microsecond burst of ~20 MeV electrons that are redirected at a...
Correlated error bursts causing decoherence in superconducting qubits have been detrimental to quantum error correction schemes, with recent work by Google showing approximately once per hour correlated bursts in their qubits. Over the past decade, it has been shown that ionizing radiation contributes to this effect, with cosmic rays being commonly identified. However, with advent of...
In this talk we report the observation of offset charge jumps induced by external radiation in Si/SiGe quantum dots that serve as spin qubits. Such charge jumps are important for quantum dot qubits, because they directly alter the operating point of the qubit in gate voltage space, and such uncontrolled shifts can induce errors in qubit initialization, readout, and manipulation. Using the...
Spin qubits have seen much progress over recent years, proving to be an appealing candidate for scalable quantum computing with small footprints, electrical control, promising coherence times, and the industry-compatible silicon material platform. As advances are made in the spaces of control and scaling, addressing noise from various origins becomes increasingly pertinent. It has been shown...
Superconducting qubits are susceptible to transient energy deposition arising from cosmic rays and environmental radioactivity. High-energy phonons generated by particle interactions in the qubit chip substrate can create quasiparticles that temporarily degrade qubit coherence.
We investigate the qubit response under controlled irradiation using a proximal Radium-224 source. To identify...
When an ionizing particle interacts with the substrate of a superconducting qubit chip, it generates high-energy athermal phonons that propagate through the material, breaking Cooper pairs in the superconducting films and inducing quasiparticle poisoning. These non-equilibrium quasiparticles limit qubit coherence times and introduce correlated errors across large qubit arrays, posing a major...
The Superconducting Quasiparticle-Amplifying Transmon (SQUAT) is a sensor architecture targeting meV (THz) detection based on a weakly charge-sensitive transmon qubit directly coupled to a transmission line. Energy depositions in the qubit capacitor generate quasiparticles that tunnel across the Josephson junction. Each tunnel changes the qubit parity and produces a measurable signal in CW...
Radiation impacts are a leading cause of information degradation in superconducting quantum devices due to their frequency in occurrence and instigation of widespread correlated errors. Recent developments [1] have built Monte-Carlo models using Geant4 and G4CMP to track the generation of e/h pairs, phonons, and superconducting quasiparticles. Building upon this work, we have developed...
Calibrating ultra-sensitive THz/meV detectors in cryogenic environments is a challenging pursuit, as conventional fiber optics suffer greatly from loss and tunable sources are limited. A system composed of a high-frequency photomixer coupled to a hollow cylindrical waveguide is being developed to deliver tunable frequency THz photons to cryogenic sensors. This work is motivated by the need to...
The Quantum Underground Instrumentation Experimental Testbed (QUIET) is a laboratory 100 meters underground at Fermilab designed to support advanced research in quantum computing and cryogenic detectors. Equipped with a 10 mK dilution refrigerator, QUIET enables the low-background characterization of superconducting qubits and detectors in a controlled environment. Over a series of cooldowns,...
In order to understand the effects of cosmic rays on superconducting qubits we have developed a that system correlates cosmic ray events with decoherence in qubits. This system consists of a qubit chip sandwiched between two arrays of MKIDs. We recent showed that both $T_1$ and $T_2$ times decreased when events were detected on our MKIDs. Now we look to expand the capabilities of our system...
Understanding the energy transport in low-temperature detectors is essential for rare-event searches, quantum sensing applications, and studies of radiation-induced effects in matter. In this work, we extend the G4CMP framework to describe charge transport in sapphire and the collective excitations in superfluid helium as phonons and rotons. For sapphire, a material of growing interest in...
Temporal fluctuations in the energy relaxation time ($T_1$) of superconducting qubits can occur on fast and irregular timescales. A quantitative understanding of these nonstationary relaxation dynamics is important for improving qubit stability and advancing fault-tolerant quantum processors. Here, we employ a new method for continuous monitoring of qubit relaxation based on an input–output...
The impact of ionizing radiation, such as gamma rays and cosmic ray muons, on superconducting qubit chips results in the generation of electron-hole pairs in the substrate, as well as a cascade of pair-breaking phonons. These energetic phonons spread efficiently throughout the chip and create excess quasiparticles in the junction electrodes of any qubits present on the device layer. This...
Phonon-mediated detectors have emerged as a promising technology for detecting low-energy particles, such as dark matter and neutrinos. Coupling phonons with qubit technology enables the realization of highly sensitive detectors for such particles. We have incorporated phonon transport in G4CMP for several novel materials. Similarly, we have now extended this simulation to model...
The fabrication efforts of the COSMIQ group are focused on creating superconducting aluminum doped with manganese (Al/Mn) gap engineered films/circuits to utilize their low-band gap for both quantum sensing and computing purposes. Environmental radiation and cosmic rays produce phonons in substrates that can then cause Cooper pairs to break producing quasiparticles (QPs). With precise gap...
There are growing efforts to use substrate-coupled kinetic inductance detectors as athermal phonon detectors for particle detection. One challenge encountered is the significant position-dependence these detectors can exhibit, destroying energy resolution of non-collimated sources. We show this position dependence can be overcome by operating the detectors to be sensitive to thermalized...
In recent years superconducting qubits have made huge strides in performance and quality. With improved qubit quality comes increasingly strict environmental requirements. One background of concern comes from black body radiation from higher temperature stages of the dilution refrigerator. IR photons are particularly challenging to shield from as many common RF materials are transparent to...
Superconducting quantum devices (SQDs) are at the forefront of technologies to investigate scientific phenomena such as dark matter and application spaces such as quantum computing. The performance of SQDs is affected by correlated events that are produced by naturally occurring radiation. These events deposit energy into materials, including substrates, which produce secondary particles from...
The interaction between superconducting qubits and quasiparticles that tunnel across the Josephson junction can be used to detect quasiparticle-generating particle scattering events, making them promising platforms for sub-eV phonon/photon sensing. Each tunneling event can flip the qubit charge parity and may also result in energy transfer between the qubit and the quasiparticle. We present a...
Both cosmogenic and terrestrial radiation are known to contribute to errors in superconducting qubits. There are multiple types and sources of ionizing radiation that can be relevant to these qubits, such as particle showers from cosmic rays, gamma radiation from surrounding earth and building materials, and radioactivity internal to the dilution fridge or qubit package itself. To investigate...
We experimentally investigated the prospect for using superconducting transmon qubits as cryogenic quantum sensors of ionizing radiation. We interrogated a six-qubit chip with resonators inductively coupled on both sides of a central transmission line in a hanger geometry. Measurements were performed without and with a source of ionizing radiation applied, external to the cryostat at room...
The SONIQ (Sensing of Neutrinos In Qubits) collaboration aims to build arrays of superconducting qubits capable of detecting meV-scale energy deposits arising from neutrino-nucleus scattering interactions within a bulk target. We outline development of these sensors, targeting sub-eV resolution on a kg-scale germanium target. We discuss current work, touching on qubit design, the use of low Tc...
The interaction of ionizing radiation with superconducting qubits can lead to large-scale correlated errors that are problematic, as they cannot be fixed by conventional error correction techniques. These radiation induced upset events have mostly been studied using the natural radiation in the environment and manmade radioactive sources, making it difficult to directly correlate the observed...
