Double Trap

Ion trap with tunable ion height

We designed and implemented a novel surface-electrode Paul trap that produces an RF-null along the axis perpendicular to the trap surface. This architecture enables control of the ion height, between 50 μm and 300 μm above the surface, using only DC electrodes, creating a platform for precision electric-field noise detection, trapping of vertical ion strings without excess micromotion, and potential applications for scalable quantum computers with surface ion traps.

Trap layout and potentials
Fig. 1. (a) False-color microscope image of the microfabricated four-rf-electrode trap. Static voltages are applied to electrodes labeled dc, and rf electrodes are labeled rf+- according to the signal phase. (b) Top-down view of xy-plane rf pseudopotentials at a height of z = 175 μm, with electrode geometry shown for reference. (c) Side view of rf potentials.
Potential during ion shuttling
Fig. 2. Simulated shuttling of the ion perpendicular to the trap surface.

Electric-field noise vs. ion height

With the capability of shuttling the ion up and down, we can perform measurements of the electric-field noise (see SQIP). We find the distance dependence of the noise to scale as d-2.6 in our trap and a frequency dependence which is consistent with 1/f noise. With significant evidence that we are not limited by technical noise sources, our distance scaling data is consistent with a noise correlation length of about 100 μm at the trap surface.

Heating rate vs. distance
Fig. 3. Planar (blue) and normal (red) heating rates as a function of ion-surface distance for a fixed secular frequency of 1 MHz. Power-law fits are overlayed for reference.

Quantum information transfer through a classical conductor

An oscillating trapped ion induces oscillating image charges in the trap electrodes. If this current is sent to the electrodes of a second trap, it influences the motion of an ion in the second trap. The expected time for a complete exchange of the ion motions is 1 ms for a trap with a characteristic size of 50 μm. This inter-trap coupling may be used for scalable quantum computing, cooling ion species that are not directly accessible to laser cooling, non-invasive study of superconductors, and realization of hybrid systems by coupling an ion-trap quantum computer to a solid-state quantum computer, e.g. a system of Josephson junctions.

Double trap
Fig. 4. Schematic of coupling trap. The two trapping regions are located above the centers of the red squares, which are connected via an electrically floating wire. Out-of-phase RF is applied to the green electrodes, and DC is applied to the blue electrodes.

This project is supported by AFOSR project “Prototype solid state quantum interface for trapped ions”.