High-Impedance Microwave Resonators with Two-Photon Nonlinear Effects 

S. Andersson, H. Havir,  A. Ranni, S. Haldar, and V. F. Maisi 

Reference: arXiv:2403.03779

In this article, we present an experimental study of a Josephson junction -based high-impedance resonator. By taking the resonator to the limit of consisting effectively only of one junction, results in strong non-linear effects already for the second photon while maintaining a high impedance of the resonance mode. Our experiment yields thus resonators with the strong interactions both between individual resonator photons and from the resonator photons to other electric quantum systems. We also present an energy diagram technique which enables to measure, identify and analyse different multi-photon optics processes along their energy conservation lines. 

Continuous microwave photon counting by semiconductor-superconductor hybrids

S. Haldar, D. Barker, H. Havir, A. Ranni, S. Lehmann, K. A. Dick, V. F. Maisi 

Reference: arXiv:2401.06617

We present a continuous microwave photon counter based on superconducting cavity-coupled semiconductor quantum dots. The device utilizes photon-assisted tunneling in a double quantum dot with tunneling events being probed by a third dot. Our device detects both single and multiple-photon absorption events independently, thanks to the energy tunability of a two-level double-dot absorber. We show that the photon-assisted tunnel rates serve as the measure of the cavity photon state in line with the P(E) theory - a theoretical framework delineating the mediation of the cavity photon field via a two-level environment. We further describe the single photon detection using the Jaynes-Cummings input-output theory and show that it agrees with the P(E) theory predictions.

Microwave power harvesting using resonator-coupled double quantum dot photodiode

S. Haldar, D. Zenelaj, P. P. Potts, H. Havir, S. Lehmann, K. A. Dick, P. Samuelsson, and V. F. Maisi

Physical Review B (Letter) 109(8), L081403 (2024)

We demonstrate a microwave power-to-electrical energy conversion in a resonator-coupled double quantum dot. The system, operated as a photodiode, converts individual microwave photons to electrons tunneling through the double dot, resulting in an electrical current flowing against the applied voltage bias at input powers down to 1 femto-watt. The device attains a maximum power harvesting efficiency of 2%, with the photon-to-electron conversion efficiency reaching 12% in the single photon absorption regime. We find that the power conversion depends on thermal effects showing that thermodynamics plays a crucial role in the single photon energy conversion.

Energetics of Microwaves Probed by Double Quantum Dot Absorption

S. Haldar, H. Havir, W. Khan, S. Lehmann, C. Thelander, K. A. Dick, and V. F. Maisi

Phys. Rev. Lett. 130, 087003 (2023)

We explore the energetics of microwaves interacting with a double quantum dot photodiode and show wave-particle aspects in photon-assisted tunneling. The experiments show that the single-photon energy sets the relevant absorption energy in a weak-drive limit, which contrasts the strong-drive limit where the wave amplitude determines the relevant-energy scale and opens up microwave-induced bias triangles. The threshold condition between these two regimes is set by the fine-structure constant of the system. The energetics are determined here with the detuning conditions of the double dot system and stopping-potential measurements that constitute a microwave version of the photoelectric effect. 

Editor's Suggestion Phys. Rev. Lett.

Quantum dot source-drain transport response at microwave frequencies

H. Havir, S. Haldar, W. Khan, S. Lehmann, K. A. Dick, C. Thelander, P. Samuelsson, and V.F. Maisi

Phys. Rev. B 108, 205417 (2023)

Quantum dots are frequently used as charge-sensitive devices in low-temperature experiments to probe electric charge in mesoscopic conductors where the current running through the quantum dot is modulated by the nearby charge environment. Recent experiments have operated these detectors using reflectometry measurements up to gigahertz frequencies rather than probing the low-frequency current through the dot. In this work, we use an on-chip coplanar waveguide resonator to measure the source-drain transport response of two quantum dots at a frequency of 6 GHz, further increasing the bandwidth limit for charge detection. Similar to that in the low-frequency domain, the response is here predominantly dissipative. For large tunnel coupling, the response is still governed by the low-frequency conductance, in line with Landauer-Büttiker theory.