Observation of Non-Hermitian Dynamics Without Loss Using Superconducting Circuits

Non-Hermitian systems can exhibit interesting behaviors not seen in Hermitian systems, such as the presence of exceptional points where two (or more) eigenvectors collapse onto each other. Systems that exhibit these points typically involve loss and gain that considerably restricts the amount of quantum coherence. In this talk, following a proposal by Wang and Clerk [1], we present a closed, four-mode quantum system able to simulate the dynamics of a PT-dimer consisting of two coupled resonators, one with gain and the other with loss, ideally without any actual dissipation that could introduce noise. The four modes are implemented using four harmonics of a superconducting resonator. Arbitrary parametric couplings between the modes is demonstrated using a current-pumped SNAIL couple. In addition to observing the exceptional point in the complex eigenmode frequencies, we show the presence of entanglement between the four modes.

[1] Yu-Xin Wang and A. A. Clerk, “Non-Hermitian dynamics without dissipation in quantum systems”, Phys. Rev. A 99, 063834 (2019)