Towards an integrated ion trap-cavity system with strong coupling for multiple ions

• Main Author: Morphew, Jack
• Other Authors: Ulbricht, Hendrik
• Published: University of Southampton 2016
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.729621

Precise control over internal states of atomic ions in ion traps has been possible for many years enabling high precision spectroscopy of atomic transitions. Trapped ions are suitable candidates for quantum information processing due to their longstorage times, low decoherence rates and high readout efficiency. Recent advances in micro-machining fibre optic mirrors and integrated fibre optic-ion trap systems for cavity QED allows one to realise strong coupling between an ion and a cavity mode by reducing the mode volume. For strong ion-cavity coupling, deterministic transfer of quantum states between ions and photons is possible. We have designed and constructed a miniaturised linear Paul trap with an integrated optical cavity, intended for coupling multiple ions to the cavity mode. The RF-electrode separation is 50μm, while the endcap separation is 350μm. The endcap electrodes are narrow tubes of inner diameter 300μm allowing optical fibers through the tubes to form the cavity. The trap depth we calculate to be 650meV for a 10V applied potential at 20MHz. The 4P_1⁄2→ 3D_3⁄2 transition of the atomic ion 40Ca+ with Γ = 24π × 22MHz can be coupled to an optical fibre Fabry-Perot cavity with length of 380µm, finesse of 33,000 and cavity linewidth k = 2π ×11MHz. The ion-cavity coherent coupling g = 2π × 19:5MHz of this system will put it in single-ion strong coupling regime with cooperativity, C=1.5.