Related papers: Quantifying surface losses in superconducting alum…
Encapsulation layers are explored for passivating the surfaces of silicon to reduce optical absorption in the 1500-nm wavelength band. Surface-sensitive test structures consisting of microdisk resonators are fabricated for this purpose.…
Hydrogen contamination in Josephson junctions is a potential source of device-to-device variability and two-level-system loss in superconducting qubits. In this work, we investigate hydrogen incorporation in oxidized aluminum barriers by…
Resonators and qubits with a niobium (Nb) base metal layer achieve some of the highest coherence times in superconducting quantum devices. The performance of such devices is often limited by loss associated with two-level systems, which are…
Low-loss superconducting rf devices are required when used for quantum computation. Here, we present a series of measurements and simulations showing that conducting losses in the packaging of our superconducting resonator devices affect…
Surface oxides contribute to losses in superconducting transmon devices resulting in degraded performance. We explore the use of the damascene process to replace the sidewall native oxide of a device with a metal/substrate interface. We…
Performance of superconducting resonators, particularly cavities for particle accelerators and micro cavities and thin film resonators for quantum computations and photon detectors has been improved substantially by recent materials…
A major roadblock to scalable quantum computing is phase decoherence and energy relaxation caused by qubits interacting with defect-related two-level systems (TLS). Native oxides present on the surfaces of superconducting metals used in…
Mesoscopic Josephson junctions (JJs), consisting of overlapping superconducting electrodes separated by a nanometer thin oxide layer, provide a precious source of nonlinearity for superconducting quantum circuits and are at the heart of…
High kinetic inductance materials constitute a valuable resource for superconducting quantum circuits and hybrid architectures. Superconducting granular aluminum (grAl) reaches kinetic sheet inductances in the nH/$\square$ range, with…
We present a superconducting microresonator thermometer based on two-level systems (TLS) that is drop-in compatible with cryogenic microwave systems. The operational temperature range is 50-1000~mK (which may be extended to 5~mK), and the…
The ability to exfoliate layered materials down to the single layer limit has opened the opportunity to understand how a gradual reduction in dimensionality affects the properties of bulk materials. Here we use this top-down approach to…
We present a circuit QED experiment in which a separate transmission line is used to address a quasi-lumped element superconducting microwave resonator which is in turn coupled to an Al/AlO$_{x}$/Al Cooper-pair box (CPB) charge qubit. In…
In superconducting quantum devices, air bridges enable increased circuit complexity and density as well as mitigate the risk of microwave loss arising from mode mixing. We implement aluminum air bridges using a simple process based on…
We present a low-loss integrated photonics platform in the visible and near ultraviolet regime. Fully-etched waveguides based on atomic layer deposition (ALD) of aluminum oxide operate in a single transverse mode with $<$3 dB/cm propagation…
Lumped-element inductors are an integral component in the circuit QED toolbox. However, it is challenging to build inductors that are simultaneously compact, linear and low-loss with standard approaches that either rely on the geometric…
We have measured the number of quasiparticles and their lifetime in aluminium superconducting microwave resonators. The number of excess quasiparticles below 160 mK decreases from 72 to 17 $\mu$m$^{-3}$ with a 6 dB decrease of the microwave…
A laser scanning microscope with a thermal spot size of about 4 $\mu$m is used to measure a quantity proportional to the rf current density in an operating superconducting co-planar waveguide microwave resonator. The twinning of the…
We report on the fabrication and characterization of superconducting coplanar waveguide (CPW) resonators based on titanium nitride (TiN) thin films deposited on 200\,mm diameter high-resistivity Si(100) substrates. We systematically…
Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting a gated InAs-Al Josephson junction to a coplanar waveguide resonator,…
We present two prescriptions for broadband (~77 - 252 GHz), millimeter-wave antireflection coatings for cryogenic, sintered polycrystalline aluminum oxide optics: one for large-format (700 mm diameter) planar and plano-convex elements, the…