Microwave Driven Transport in Mesoscopic Superconducting Junctions

Apostol Vourdas

J. Basset

This manuscript summarizes my research activities devoted to the study of nonequilibrium phenomena in mesoscopic superconducting and semiconducting circuits. The work develops along two directions: the dynamics of metallic Josephson junctions driven out of equilibrium and the interaction between electrons and microwave photons in mesoscopic quantum circuits.The first part investigates diffusive superconductor–normal metal–superconductor Josephson junctions subjected to strong perturbations such as microwave irradiation or stochastic injection of high-energy quasiparticles. These experiments reveal how nonequilibrium excitations modify the Andreev spectrum and the phase dynamics of the junction. The second part addresses electron–photon coupling in mesoscopic circuits across different interaction regimes. Early work focused on semiconductor double quantum dots coupled to low-impedance microwave cavities in the weak coupling regime. Later work involved the fabrication and characterization of high-kineticinductance superconducting materials, allowing the realization of high-impedance resonators and stronger light-matter coupling. Finally, a superconducting tunnel junction coupled to a high-impedance granular aluminum cavity allowed bath engineering based on photo-assisted quasiparticle tunneling, efficient photon-toelectron conversion, and continuous single microwave photon detection.

Kazuhiro Yoshida, K. Hamasaki, Fumi Irie +1 more

Laura Borgongino, Rubén Seoane Souto, José Luis del Olmo +4 more

Non-reciprocal transport underpins key functionalities in signal processing and logic; however, conventional semiconductor diodes exhibit reduced performance at sub-Kelvin temperatures. As cryogenic electronics continue to scale, there is increasing demand for diode operation compatible with low-temperature and low-dissipation conditions. This need has driven the development of alternatives to p-n junctions that rely on non-reciprocal electron transport mechanisms efficient in the deep-cryogenic regime. Superconducting devices constitute a natural low-loss platform, yet most existing superconducting diodes are restricted to either Cooper-pair or quasiparticle transport, often requiring complex material stacks, asymmetric geometries, or external magnetic fields. No single, geometrically symmetric junction has yet integrated rectification across both transport channels to achieve vanishing resistance under forward bias and strongly suppressed conduction under reverse bias. Here, we demonstrate a dynamically reconfigurable dual-function superconducting diode based on a conventional Al/AlOx/Al tunnel junction. Via microwave biharmonic driving, we exploit multi-tone photon-assisted tunneling to independently control dissipationless and dissipative transport channels within the same device. Varying the microwave drive amplitude induces a transition from a supercurrent diode to an ideal quasiparticle diode, achieving rectification efficiencies exceeding those of conventional Schottky diodes and contemporary superconducting diodes. We further demonstrate AC signal rectification under both current-bias and voltage-bias configurations. Finally, we implement a proof-of-concept "absolute diode" that combines zero forward resistance with strongly suppressed reverse conduction. This tunable approach provides a versatile building block for low-power cryogenic electronic architectures.

Sidney Shapiro, ANDRE R. JANUS, Sándor Holly

Benjamin Remez, Pouyan Ghaemi, Jay Deep Sau +1 more

Superconducting weak-link junctions host electron--hole hybridized excitations called Andreev bound states, central to mesoscopic transport and emerging quantum information platforms. Andreev physics has so far been synonymous with the microwave range. However, advancements in superconductor--semiconductor hybrid junctions open the door to the characterization, and manipulation, of Andreev states by light. Here we introduce a model for light--Andreev interaction, with distinct features: Electrons transitioning into Andreev levels can sidestep Pauli exclusion, resulting in two optical absorption resonances separated by twice the bound state energy. One resonance populates the Andreev state and the other empties it, enabling optical control of Andreev qubit parity; pumping both resets the junction and prevents saturation. Given their strong microwave coupling, we show how Andreev bound states can operate as optical--to--microwave transducers with MHz-scale intermode coupling, a key ingredient for heat load management and quantum networking. We illustrate these effects with realistic device parameters. Our results highlight the possibilities in the new field of Andreev optoelectronics.