Cavity sideband cooling of a single trapped ion

We report a demonstration and quantitative characterization of one-dimensional cavity cooling of a single trapped 88Sr+ ion in the resolved sideband regime. We measure the spectrum of cavity transitions, the rates of cavity heating and cooling, and the steady-state cooling limit. The cavity cooling dynamics and cooling limit of 22.5(3) motional quanta, limited by the moderate coupling between the ion and the cavity, are consistent with a simple model [Phys. Rev. A 64, 033405] without any free parameters, validating the rate equation model for cavity cooling.Comment: 5 pages, 4 figure

Integrated chips and optical cavities for trapped ion quantum information processing

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 145-158).Quantum information processing is a new and exciting field which uses quantum mechanical systems to perform information processing. At the heart of the excitement are quantum computation - which promises efficient algorithms for simulating physical systems, factoring, and searching unsorted databases - and quantum communication - which provides a provably secure communications protocol. Trapped ions show much promise for achieving large-scale quantum information processing. Experiments thus far have demonstrated small algorithms and entanglement of two remote ions. Current work focuses on scaling to large numbers of ions for quantum computation and interconversion between trapped ions and photons for quantum communication. This thesis addresses some of the challenges facing scaling and interconversion for trapped ion quantum information processing. The first part of the thesis describes the development of scalable, multiplexed ion trap chips for quantum computation. The ion trap chips are based on a new ion trap geometry, called the surface-electrode trap, in which all of the electrodes reside in a single plane. Three generations of surface-electrode traps are designed, fabricated, and tested - culminating with the demonstration of an ion trap chip microfabricated using standard silicon VLSI materials and processes for scalability to small trap size and large arrays of interconnected ion traps. The second part of the thesis presents an experiment that demonstrates cavity cooling, a method of laser cooling the motional state of trapped ions without decohering the internal qubit state.(cont.) Cavity cooling is demonstrated for the first time with trapped ions, and for the first time in the parameter regime where cooling to the motional ground state is possible. The measured cavity cooling dynamics are found to agree with a rate equation model without any free parameters. The third and final part of the thesis presents a theoretical proposal for interconversion between single trapped ion qubits and single photon qubits for quantum communication. The idea is to map the state of the single ion qubit to a superradiant collective state of several ions, which then couples strongly with single photons in an optical cavity.by David R. Leibrandt.Ph.D

Field-test of a robust, portable, frequency-stable laser

We operate a frequency-stable laser in a non-laboratory environment where the test platform is a passenger vehicle. We measure the acceleration experienced by the laser and actively correct for it to achieve a system acceleration sensitivity of $\Delta f / f$ = $11(2) \times 10^{-12}$/g, $6(2) \times 10^{-12}$/g, and $4(1) \times 10^{-12}$/g for accelerations in three orthogonal directions at 1 Hz. The acceleration spectrum and laser performance are evaluated with the vehicle both stationary and moving. The laser linewidth in the stationary vehicle with engine idling is 1.7(1) Hz

Electron impact ionization loading of a surface electrode ion trap

We demonstrate a method for loading surface electrode ion traps by electron impact ionization. The method relies on the property of surface electrode geometries that the trap depth can be increased at the cost of more micromotion. By introducing a buffer gas, we can counteract the rf heating assocated with the micromotion and benefit from the larger trap depth. After an initial loading of the trap, standard compensation techniques can be used to cancel the stray fields resulting from charged dielectric and allow for the loading of the trap at ultra-high vacuum.Comment: 4 pages, 5 eps figures. Shift in focus, minor correction

Suppression of Heating Rates in Cryogenic Surface-Electrode Ion Traps

Dense arrays of trapped ions provide one way of scaling up ion trap quantum information processing. However, miniaturization of ion traps is currently limited by sharply increasing motional state decoherence at sub-100 um ion-electrode distances. We characterize heating rates in cryogenically cooled surface-electrode traps, with characteristic sizes in 75 um to 150 um range. Upon cooling to 6 K, the measured rates are suppressed by 7 orders of magnitude, two orders of magnitude below previously published data of similarly sized traps operated at room temperature. The observed noise depends strongly on fabrication process, which suggests further improvements are possible.Comment: 4 pages, 4 figure

Temperature Dependence of Electric Field Noise Above Gold Surfaces

Electric field noise from fluctuating patch potentials is a significant problem for a broad range of precision experiments, including trapped ion quantum computation and single spin detection. Recent results demonstrated strong suppression of this noise by cryogenic cooling, suggesting an underlying thermal process. We present measurements characterizing the temperature and frequency dependence of the noise from 7 to 100 K, using a single Sr+ ion trapped 75 um above the surface of a gold plated surface electrode ion trap. The noise amplitude is observed to have an approximate 1/f spectrum around 1 MHz, and grows rapidly with temperature as T^beta for beta from 2 to 4. The data are consistent with microfabricated cantilever measurements of non-contact friction but do not extrapolate to the DC measurements with neutral atoms or contact potential probes.Comment: 4 pages, 3 figures, 1 tabl

Laser ablation loading of a surface-electrode ion trap

We demonstrate loading by laser ablation of $^{88}$Sr$^+$ ions into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 3-5 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth (40 meV) below where electron impact ionization loading is typically successful ($\gtrsim$ 500 meV).Comment: 4 pages, 4 figure