Protected Josephson Rhombus chains.

We have studied the low-energy excitations in a minimalistic protected Josephson circuit which contains two basic elements (rhombi) characterized by the π periodicity of the Josephson energy. Novel design of these elements, which reduces their sensitivity to the offset charge fluctuations, has been employed. We have observed that the lifetime T1 of the first excited state of this quantum circuit in the protected regime is increased up to 70  μs, a factor of ∼100 longer than that in the unprotected state.

Communication via the statistics of photon-number squeezed light.

A method of communication employing the second order statistics of photon-number squeezed light is demonstrated. The technique encodes the information content in both nonstationary noise processes and in the average optical power, thereby creating two orthogonal channels and increasing the transmission capacity. Communication via the fragile quantum state has potential applications for privatized communication.