High quality superconducting resonators for QND Measurements of Qubits and Sensitive Photon Detections

Jonas Stasys Zmuidzinas, Peter K. Day, Jian Gao +7 more

Roberto Moretti, Hervè Atsè Corti, Danilo Labranca +54 more

Quantum Sensing is a rapidly expanding research field that finds one of its applications in Fundamental Physics, as the search for Dark Matter. Devices based on superconducting qubits have already been successfully applied in detecting few-GHz single photons via Quantum Non-Demolition measurement (QND). This technique allows us to perform repeatable measurements, bringing remarkable sensitivity improvements and dark count rate suppression in experiments based on high-precision microwave photon detection, such as for Axions and Dark Photons search. In this context, the INFN Qub-IT project goal is to realize an itinerant single-photon counter based on superconducting qubits that will exploit QND for enhancing Axion search experiments. In this study, we present Qub-IT's status towards the realization of its first superconducting qubit device, illustrating design and simulation procedures and the characterization of fabricated Coplanar Waveguide Resonators (CPWs) for readout. We match target qubit parameters and assess a few-percent level agreement between lumped and distributed element simulation models. We reach a maximum internal quality factor of 9.2×105for -92 dBm on-chip readout power.

Ivan N. Zhilyaev

Sarah Sheldon, Martin Sandberg, Hanhee Paik +4 more

We present a method for detecting electromagnetic (EM) modes that couple to a superconducting qubit in a circuit quantum electrodynamics architecture. Based on measurement-induced dephasing, this technique allows the measurement of modes that have a high quality factor (Q) and may be difficult to detect through standard transmission and reflection measurements at the device ports. In this scheme, the qubit itself acts as a sensitive phase meter, revealing modes that couple to it through measurements of its coherence time. Such modes are indistinguishable from EM modes that do not couple to the qubit using a vector network analyzer. Moreover, this technique provides useful characterization parameters including the quality factor and the coupling strength of the unwanted resonances. We demonstrate the method for detecting both high-Q coupling resonators in planar devices as well as spurious modes produced by a 3D cavity.

A. Rettaroli, Leonardo Banchi, Hervè Atsè Corti +8 more

Quantum sensing is a rapidly expanding research field that finds one of its applications in fundamental physics, as the detection of light Dark Matter. Qubit-based superconducting devices have already been successfully applied in detecting few-GHz single photons via Quantum Non-Demolition measurements. The optimization and new design schemes of circuits embedding qubits will yield notable enhancements in sensitivity and suppression of dark count rates in experiments involving high-precision microwave photon detection, particularly in the search for Axions and Dark Photons. The Qub-It collaboration is developing a novel microwave photon detection scheme based on two qubits coupled to the same resonator, both in 2D and 3D formats.

Joel Strand