Generation of Nonclassical Photons in a Josephson-Junction Cavity

Paolo Rosson

Noriyuki Hatakenaka, Tetsuo Ogawa

Mircea Trif, Pascal Simon

We study a voltage-biased Josephson junction coupled to two resonators of incommensurate frequencies. Using a density matrix approach to analyze the cavity fields and an input-output description to analyze the emitted photonic fluxes and their correlation functions, we have shown, both for infinite- and finite-bandwidth detectors, that the emitted radiation is nonclassical in the sense that the correlators violate Cauchy-Schwarz inequalities. We have also studied the time dependence of the photonic correlations and showed that their linewidth becomes narrower with the increase of the emission rate approaching from below the threshold limit.

Rahul Trivedi, Daniil M. Lukin, Jelena Vuckovic A

Simon Dambach, Björn Kubala, Vera Gramich +1 more

The interplay of the tunneling transfer of charges and the emission and absorption of light can be investigated in a setup, where a voltage-biased Josephson junction is connected in series with a microwave cavity. We focus here on the emission processes of photons and analyze the underlying time-dependent statistics using the second-order correlation function ${g}^{(2)}(\ensuremath{\tau})$ and the waiting-time distribution $w(\ensuremath{\tau})$. Both observables highlight the crossover from a coherent light source to a single-photon source. Due to the nonlinearity of the Josephson junction, tunneling Cooper pairs can create a great variety of nonclassical states of light even at weak driving. Analytical results for the weak driving as well as the classical regime are complemented by a numerical treatment for the full nonlinear case. We also address the question of possible relations between ${g}^{(2)}(\ensuremath{\tau})$ and $w(\ensuremath{\tau})$ as well as the specific information which is provided by each of them.

Alessandro Zavatta, Valentina Parigi, Marco Bellini