arXiv subjects

Kenneth M. O'Hara

Publications and source records attributed to Kenneth M. O'Hara.

5 recordsLinked to original sources

arXiv2026

High-Temporal-Resolution Measurements of the Impacts of Ionizing Radiation on Superconducting Qubits

We measure the effect of ionizing radiation on superconducting qubits with a timing resolution of 1 $μs$ using microwave kinetic inductance detectors (MKIDs) fabricated on the same substrate. We observe no correlation between two-level system (TLS) scrambling events and ionizing radiation events detected with the MKIDs, suggesting TLS scrambling events may not arise from ionizing radiation and instead the previously reported apparent correlation may be due to events without sufficient energy to trigger our MKIDs. We characterize the fast-time system recovery of transmons following a radiation event, where we observe the recovery of the enhanced qubit relaxation and excitation to be well-described by an exponential recovery to the baseline quasiparticle density, with a characteristic time of $13\pm1\ μ$s, and a peak quasiparticle density at the junction per deposited energy of $240/μm^3/MeV$. The fast recovery is consistent with literature reported values for Nb-based devices with direct injection of 2$Δ_{\text{Al}}$ phonons, demonstrating the recovery is strongly dependent on the proximity of niobium to the junction.

quant-ph↗

arXiv2020

Suppression of Three-Body Loss Near a p-Wave Resonance Due to Quasi-1D Confinement

We investigate the three-body recombination rate of a Fermi gas of $^6$Li atoms confined in quasi-1D near a $p$-wave Feshbach resonance. We confirm that the quasi-1D loss rate constant $K_3$ follows the predicted threshold scaling law that $K_3$ is energy independent on resonance, and find consistency with the scaling law $K_3 \propto (k \, a_{1D})^6$ far from resonance [Mehta et al. Phys. Rev. A 76, 022711 (2007)]. Further we develop a theory based on Breit-Wigner analysis that describes the loss feature for intermediate fields. Lastly we measure how the loss rate constant scales with transverse confinement and find that $K_3 \propto V_L^{-1}$, where $V_L$ is the lattice depth. Importantly, at our attainable transverse confinements and temperatures, we see a 74-fold suppression of the on-resonant three-body loss rate constant in quasi-1D compared to 3D. With significant further enhancement of the transverse confinement, this suppression may pave the way for realizing stable $p$-wave superfluids.

physics.atom-ph↗

arXiv2015

A self-injected, diode-pumped, solid-state ring laser for laser cooling of Li atoms

We have constructed a solid-state light source for experiments with laser cooled lithium atoms based on a Nd:YVO$_4$ ring laser with second-harmonic generation. Unidirectional lasing, an improved mode selection, and a high output power of the ring laser was achieved by weak coupling to an external cavity which contained the lossy elements required for single frequency operation. Continuous frequency tuning is accomplished by controlling two PZTs in the internal and the external cavities simultaneously. The light source has been utilized to trap and cool fermionic lithium atoms into the quantum degenerate regime.

physics.atom-ph↗

arXiv2014

The three-body parameter for Efimov states in lithium-6

We present a state-of-the-art reanalysis of experimental results on Efimov resonances in the three-fermion system of $^6$Li. We discuss different definitions of the 3-body parameter (3BP) for Efimov states, and adopt a definition that excludes effects due to deviations from universal scaling for low-lying states. We develop a finite-temperature model for the case of three distinguishable fermions and apply it to the excited-state Efimov resonance to obtain the most accurate determination to date of the 3BP in an atomic three-body system. Our analysis of ground-state Efimov resonances in the same system yields values for the three-body parameter that are consistent with the excited-state result. Recent work has suggested that the reduced 3BP for atomic systems is a near-universal quantity, almost independent of the particular atom involved. However, the value of the 3BP obtained for $^6$Li is significantly ($\sim 20$%) different from that previously obtained from the excited-state resonance in Cs. The difference between these values poses a challenge for theory.

cond-mat.quant-gas↗

arXiv2012

S-Wave Collisional Frequency Shift of a Fermion Clock

We report an s-wave collisional frequency shift of an atomic clock based on fermions. In contrast to bosons, the fermion clock shift is insensitive to the population difference of the clock states, set by the first pulse area in Ramsey spectroscopy, θ_1. The fermion shift instead depends strongly on the second pulse area θ_2. It allows the shift to be canceled, nominally at θ_2 = π/2, but correlations shift the null to slightly larger θ_2. The shift applies to optical lattice clocks and increases with the spatial inhomogeneity of the clock excitation field, naturally large at optical frequencies.

physics.atom-ph↗