Quantum Interfaces between Ions and Circuits
It is expected that future quantum information processors will be hybrid systems. Such systems will use the distinct advantages of different physical systems to implement different components of a quantum computing architecture. The long coherence times of trapped ions along with the fast gate times of superconducting circuits make them promising candidates for such devices. Unfortunately, these systems display a large mismatch in characteristic frequencies, rendering standard Coulombic interactions ineffective at coherently transferring information between them. In this talk I'll describe two related techniques for coupling a trapped ion’s motion to the fundamental mode of a superconducting circuit. In order to overcome the resonance mismatch, we effectively modulate either the inductance or capacitance of the circuit. Studying the motion of the corresponding classical oscillator, I will show how to add sidebands to the circuit's charge fluctuations that are resonant with the ion's motion. This allows for an effective `beam-splitter'-like interaction between the systems, with coupling strengths on the order of 10's of kHz. We find a generic expression for the coherent coupling strength, showing that an inductive drive is significantly weaker than capacitive driving when the ion and circuit are coupled.