Chen-Kuan Chou

Efficient fluorescence collection and ion imaging with the “tack” ion trap

Trapped, laser-cooled atoms and ions produce intense fluorescence of the order 107~108 photons per second. Detection of this fluorescence enables efficient measurement of the quantum state of qubits based on trapped atoms. It is desirable to collect a large fraction of the photons to make the detection faster and more reliable. Additionally, efficient fluorescence collection can improve the speed and fidelity of remote ion entanglement and quantum gates. Refractive and reflective optics, and optical cavities have all been used to collect the trapped ion fluorescence with up to about 10% efficiency. Here we show a novel ion trap design that incorporates a metallic spherical mirror as the integral part of the trap itself, being its RF electrode. The mirror geometry enables up to 35% solid angle collection of trapped ion fluorescence. The movable central pin electrode of this trap allows precise placement of the ion at the focus of the reflector. We characterize the performance of the mirror, and measure 25% collection efficiency, likely limited by the imperfections of the mirror surface. We also study the properties of the images of single ions formed by the spherical mirror and apply aberration correction with an aspherical element placed outside the vacuum system. Owing to the simplicity of its design, this trap structure can be adapted for microfabrication and integration into more complex trap architectures.Trapped, laser-cooled ions produce intense fluorescence. Detecting this fluorescence enables efficient measurement of quantum state of qubits based on trapped atoms. It is desirable to collect a large fraction of the photons to make the detection faster and more reliable. Additionally, efficient fluorescence collection can improve speed and fidelity of remote ion entanglement and quantum gates. Here we show a novel ion trap design that incorporates metallic spherical mirror as the integral part of the trap itself, being its RF electrode. The mirror geometry enables up to 35% solid angle collection of trapped ion fluorescence; we measure a 25% effective solid angle, likely limited by imperfections of the mirror surface. We also study properties of the images of single ions formed by the mirror and apply aberration correction. Owing to the simplicity of its design, this trap structure can be adapted for micro-fabrication and integration into more complex trap architectures.

Toward a scalable quantum computing architecture with mixed species ion chains

We report on progress toward implementing mixed ion species quantum information processing for a scalable ion-trap architecture. Mixed species chains may help solve several problems with scaling ion-trap quantum computation to large numbers of qubits. Initial temperature measurements of linear Coulomb crystals containing barium and ytterbium ions indicate that the mass difference does not significantly impede cooling at low ion numbers. Average motional occupation numbers are estimated to be

Note: Single ion imaging and fluorescence collection with a parabolic mirror trap

\bar{n} \approx 130

Ion–photon entanglement and Bell inequality violation with 138 Ba +

n¯≈130 quanta per mode for chains with small numbers of ions, which is within a factor of three of the Doppler limit for barium ions in our trap. We also discuss generation of ion–photon entanglement with barium ions with a fidelity of

Remote entanglement of ions in parabolic mirror traps

F \ge 0.84

Efficient fluorescence collection and ion imaging with the ``tack'' ion trap

F≥0.84, which is an initial step towards remote ion–ion coupling in a more scalable quantum information architecture. Further, we are working to implement these techniques in surface traps in order to exercise greater control over ion chain ordering and positioning.