We characterized a monolithic quantum communication device utilizing a trapped ion in a surface-electrode trap and an integrated micro Fabry-Perot cavity. Cavity characterization yields estimated collection efficiency of 40% with cooperativity of 2.3.
Ion trap systems allow the faithful storage and manipulation of qubits encoded in the energy levels of the ions, and can be interfaced with photonic qubits that can be transmitted to connect remote quantum systems. Single photons transmitted from two remote sites, each entangled with one quantum memory, can be used to entangle distant quantum memories by interfering on a beam splitter. Efficient remote entanglement generation relies upon efficient light collection from single ions into a single mode fiber. This can be realized by integrating an ion trap with an optical cavity and employing the Purcell effect for enhancing the light collection. Remote entanglement can be used as a resource for a quantum repeater for provably secure long-distance communication or as a method for communicating within a distributed quantum information processor. I present the integration of a 1 mm optical cavity with a micro-fabricated surface ion trap. The plano-concave cavity is oriented normal to the chip surface where the planar mirror is attached underneath the trap chip. The cavity is locked using a 780 nm laser which is stabilized to Rubidium and shifted to match the 369 nm Doppler transition in Ytterbium. The linear ion trap allows ions to be shuttled in and out of the cavity mode. The Purcell enhancement of spontaneous emission into the cavity mode would then allow efficient collection of the emitted photons, enabling faster remote entanglement generation.
This thesis describes the use of diffractive mirrors for efficient collection of photons from an ion in a modern surface Paul trap. Ion light collection is one of the important steps of most of the quantum computing and communication protocols using trapped ions and has a direct effect on the performance of these protocols. This is the first demonstration of an integrated-optic for a surface ion trap and a step towards realizing scalable quantum computing and communication using trapped ions. These mirrors are monolithically integrated onto the ground electrode of the trap. The fabrication of the mirrors has been accomplished by patterning diffraction rings on the silicon dioxide substrate of the trap chip and then coating it with aluminium to form a diffractive mirror integrated onto the electrode. We verified that the altered trap is still functional and demonstrated that thesemirrors substantially increase the efficiency of free space ion light collection and ion light single mode bre coupling. The mirror design is aberration free and we demonstrated this by obtaining near Diffraction-limited images of an ion. To measure the collection efficiency of the diffractive mirrors, we performed a single photon generation protocol based on an optical pumping scheme and one chapter of this thesis describes the implementation of this scheme.
In ion trap quantum information processing, efficient fluorescence collection is critical for fast, high-fidelity qubit detection and ion–photon entanglement. The expected size of future many-ion processors requires scalable light collection systems. We report on the development and testing of a microfabricated surface-electrode ion trap with an integrated high-numerical aperture (NA) micromirror for fluorescence collection. When coupled to a low-NA lens, the optical system is inherently scalable to large arrays of mirrors in a single device. We demonstrate the stable trapping and transport of 40 Ca + ions over a 0.63 NA micromirror and observe a factor of 1.9 enhancement of photon collection compared to the planar region of the trap.
We have fabricated and characterized laser-ablated micromirrors on fused silica substrates for constructing stable Fabry–Perot optical cavities. We highlight several design features which allow these cavities to have lengths in the 250–300 μm range and be integrated directly with surface ion traps. We present a method to calculate the optical mode shape and losses of these micromirror cavities as functions of cavity length and mirror shape, and confirm that our simulation model is in good agreement with experimental measurements of the intracavity optical mode at a test wavelength of 780 nm. We have designed and tested a mechanical setup for dampening vibrations and stabilizing the cavity length, and explore applications for these cavities as efficient single-photon sources when combined with trapped Yb171+ ions.
Trapped ions are a leading candidate for the “stationary qubits” of a quantum network. However, thus far remote entanglement rates have primarily been limited by low photon collection efficiency. In this work, we propose an architecture for a long-range, high-entanglement-rate quantum repeater. Our strategy involves using a micromirror fiber-based cavity, integrated with a surface electrode trap at cryogenic temperatures, to achieve high photon collection efficiency while maintaining high mechanical stability and low ion motional heating. The emitted photons can be efficiently and coherently converted to telecom wavelengths, facilitating long-distance networking.