Quantum computation by non-Abelian Majorana zero modes (MZMs) offers an approach to achieve fault tolerance by encoding quantum information in the non-local charge parity states of semiconductor nanowire networks in the topological superconductor regime. Thus far, experimental studies of MZMs chiefly relied on single electron tunneling measurements, which lead to the decoherence of the quantum information stored in the MZM. As a next step towards topological quantum computation, charge parity conserving experiments based on the Josephson effect are required, which can also help exclude suggested non-topological origins of the zero bias conductance anomaly. Here we report the direct measurement of the Josephson radiation frequency in indium arsenide nanowires with epitaxial aluminium shells. We observe the 4π-periodic Josephson effect above a magnetic field of ≈200 mT, consistent with the estimated and measured topological phase transition of similar devices.

One-dimensional (1D) interacting electronic systems exhibit distinct properties when compared to their counterparts in higher dimensions. We report Coulomb drag measurements between vertically integrated quantum wires separated by a barrier only 15 nanometers wide. The temperature dependence of the drag resistance is measured in the true 1D regime where both wires have less than one 1D subband occupied. As a function of temperature, an upturn in the drag resistance is observed below a temperature T* ~ 1.6 kelvin. This crossover in Coulomb drag behavior is consistent with Tomonaga-Luttinger liquid models for the 1D-1D drag between quantum wires.