Fused silica ion trap chip with efficient optical collection system for timekeeping, sensing, and emulation

ABSTRACT: We will design, fabricate and test a quantum processing unit (QPU) based on a symmetric ion trap chip. The trap will provide trapping depth similar to that obtain with macrosize Paul traps. In addition to the ion trap, this chip will incorporate integrated optical systems which will deliver the light fields required by the elementary quantum processing unit (or quantum sensing unit). The design will be supported by simulations of the optical and electro-magnetic systems. Our QPU chip will be made from fused silica, a material that is transparent at the wavelengths of interest, and which has good RF characteristic. The material transparency allows for optical beams to approach the trap from all directions. Three optical interfaces (two inputs and one collection) will be integrated into our chip substrate. The two input assemblies will deliver classical light fields to the trap for ion cooling and qubit addressing. The third optical assembly will collect light from the trapped ions for the purpose of qubit state detection and matter-photon qubit interfacing. The optical interfaces will either address the ions individually or collectively. In all cases the optical assemblies will be interfaced off-chip through optical fibers. The functions that will be performed on the collective ion assembly include Doppler and sideband cooling, and repumping. The single ion functions include excitation (create qubit state), multiple qubit entanglement through trap vibrational modes, and read out (excitation + fluorescence detection). These optically-driven operations will be performed using a range of optical elements which we previously developed. Where dense or closely spaced optical pathways are required, we will rely extensively on subsurface optical waveguides with lens sections machined directly in the substrate, and with fiber / waveguide interfaces. Where high throughput and large area collection is called for, we will use high NA fiber/lens assemblies of the type demonstrated in Phase I. As part of this program we will also demonstrate the viability of our rapid-turn-around, advanced fused silica micromachining system for producing standard and custom ion-trap chips, atom chips, and chip-based (elementary) quantum processing units or quantum sensors for the research and defense communities. BENEFIT: For some times it has been recognized that trapped ions are one of the more promising candidate physical systems for large-scale quantum information processing and for ultra-sensitive quantum sensing. In order to take advantage of these opportunities, one needed to develop scalable means to fabricate chips with high-quality traps and integrated optics. The combination of a microtrap with deep trapping potential and integrated and miniaturized optical interface features will facilitate the use of ion-trap chips in many applications. Our proposed integration of optics with a chip trap has the potential to critically transform the use of ion traps for the collection of atomic fluorescence for motion/force sensors through Doppler velocimetry and the efficient collection of single photons from trapped ions for applications in fast single photon sources, quantum repeater circuitry, and high fidelity remote entanglement of atoms for quantum information protocols Our proposal brings to large-scale quantum information processing and ultra-sensitive quantum sensing a microfabrication capability that will support the transition from the present one of a kind research and development chip fabrication to the mass-producing of standardized quantum chips.