Graduate and Postdoc Fellow Seminar: Jayameenakshi Venkatraman

Floquet engineering with superconducting circuits

In the quantum world, it seems there is always a path to escape from a trap since energy is not conserved on very short time scales, allowing quantum fluctuations to overcome an energy barrier. The tunnel effect is the most striking manifestation of this quantum escape game and has no classical counterpart. However, counterintuitively, if a second path is also available, the two paths can be arranged so that they destructively interfere with each other, thus blocking the escape. This interference is also a quantum- mechanical feature and enters here to null out the freedom provided by quantum tunneling. Furthermore, the two paths can also be arranged so that they interfere constructively, now enhancing tunneling instead of suppressing it. Thus, by controlling the phase difference between the two paths, one can control the intensity of tunneling in a way that is completely independent of the barrier height, a favorable situation with applications in quantum computation, and in molecular and nuclear physics. Our experiment has for the first time quantitatively demonstrated this interference effect in a controlled tunneling double-well system.