QOSC2007 · Coupling of trapped ions via normal metal and superconductor transmission lines

In the efforts to implement an ion-trap quantum computer, there exists an urgent need to couple trapped ions and transfer quantum information between them. We are proposing an experimental investigation of coupling ions, trapped in separate ion-traps, via normal-metallic and superconducting transmission lines. Motion of a trapped ion placed in the vicinity of a conducting electrode induces currents in the electrode. This process allows coupling of different ions by tuning the ion motional frequencies. Coherent transfer of the quantum state between different ions will depend on the properties of electronic transport through the electrode. In specific, the presence of the macroscopically coherent BCS condensate in the superconductor is expected to reduce the effect of various decoherence sources on the quantum state transfer. Our investigation will focus on the degree of coherent coupling achieved at cryogenic temperatures, when the transmission line is in the normal state and as it is cooled through the superconducting transition temperature. This will be a significant step towards the realization of coupled trapped-ion qubits towards the goal of implementing a scalable quantum computer and in interfacing ion and superconducting qubits. The proposed process can also be used to cool ion-species not accessible to laser cooling. In addition, it can give rise to a new set of experimental tools for studying electronic transport and noise in normal metals and superconductors.