Utilization of the superconducting transition for characterizing low-quality-factor superconducting resonators

Abstract

Characterizing superconducting microwave resonators with highly dissipative elements is a technical challenge, but a requirement for implementing and understanding the operation of hybrid quantum devices involving dissipative elements, e.g. for thermal engineering and detection. We present experiments on λ/4 superconducting niobium coplanar waveguide (CPW) resonators, terminating at the antinode by a dissipative copper microstrip via aluminum leads, such that the resonator response is difficult to measure in a typical microwave environment. By measuring the transmission both above and below the superconducting transition of aluminum, we are able to isolate the resonance. We then experimentally verify this method with copper microstrips of increasing thicknesses, from 50 nm to 150 nm, and measure quality factors in the range of 10 ∼ 67 in a consistent way. arXiv:1904.01781v2 [cond-mat.supr-con]

Heat rectification via a superconducting artificial atom

“…We observe qubit-resonator couplings at 2.75 GHz, corresponding to the low frequency resonator, 5.5 GHz, corresponding to the second mode of this resonator, and at 7.05 GHz, corresponding to the high frequency resonator. We note, however, that there is broadening of these lines when the copper termination is present, as reported in [26].…”

Colloquium: Quantum heat transport in condensed matter systems

“…The qubit is coupled capacitively (coupling g) to two nominally identical superconducting coplanar wave resonators that act as LC resonators with resonant frequencies of ∼5 GHz each. For thermal transport experiments the λ=4 resonators are terminated by on-chip resistors that form the controlled dissipative elements in the circuit (Chang et al, 2019). The dissipation is then given by the inverse of the quality factor of the resonator and can be quantified by another coupling parameter γ.…”

A Cooper-Pair Box Coupled to Two Resonators: An Architecture for a Quantum Refrigerator

“…Numerical simulations of cooling power in a Cooperpair box acting as a quantum Otto refrigerator, for various values of the environment temperature. We use realistic values of the resonators quality factor Qc = Q h = 3 [21,24,25], Tc = T h = 300 mK, and with a = 2. For the most pessimistic case of a 1 K environmental temperature we can achieve ∼ 40 aW of cooling power, detectable using standard normal metal-insulator-superconductor thermometry techniques.…”

“…c-QED has enjoyed a striking period of advancement, with numerous studies demonstrating strong coupling of photons to various types of qubits [15][16][17], with a broad range of applications [18][19][20]. Furthermore, modern nanofabrication techniques allow the integration and characterization of superconducting qubits coupled to normal-metal dissipative elements [21], creating hybrid c-QED systems capable of probing thermal transport in quantum systems. Such systems differentiate themselves from previous attempts on quantum heat engines via their unambiguous implementation of thermal reservoirs, which naturally define the bath temperature, and possess a multitude of techniques for both primary and secondary thermometry [22,23].…”