Ultrasensitive on-chip spectroscopy of Bloch oscillations and nonclassical radiation in small Josephson junctions

• Applicants: Professor Dr. Fabian Hassler; Dr. Sergey Lotkhov
• Subject Area: Experimental Condensed Matter Physics ; Theoretical Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445530728

The goal of the proposal is to gain a profound understanding of Bloch oscillation dynamics in small Josephson junctions in the nA-current (GHz-frequency) range. Quantised Bloch currents, I_B = 2exf_B, in this range of Bloch frequency f_B, are of great interest for metrology, but their realization is challenging. In most of the previous attempts, it was difficult to approach the Bloch oscillations regime, because of thermal and quantum noise leading to dephasing. We propose to circumvent these issues by using an integrated state-of-the-art microwave circuit, which enables highly sensitive low-loss readout and spectroscopy of Bloch oscillations on-chip. Dedicated theory support will guide the experiments to tune the parameters to the sweet spot which allows for the observation of underdamped oscillations. Furthermore, by linking the Bloch- and the Josephson, f_J = 2eV_J/h, oscillation frequencies to that of a high-quality local resonator mode, f_B = f_J = f_R, we will test the feasibility of an alternative realization of the von-Klitzing resistance quantum, R_k = h/4e^2 = V_J/I_B referred to as the “superconducting Quantum-Hall effect”. Here, V_J is the Josephson voltage. An important part of our project will be to investigate theoretically the non-classical radiation that is present in the resonator mode as well as the statistics of the photons that are emitted from the phase-locked system below the classical threshold of instability.

• DFG Programme: Research Grants