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SESSION 3: Ion Trap QIP - Alvarado "D"
Session Chair:
8:30am-9:00amUlrich Warring, NIST Ion Storage Group; National Institute of Standards and Technology
Trapped-ion quantum information processing experiments at NIST*

Abstract. In our experiments we employ internal states of trapped and laser-cooled ions as qubits. Typically, laser light is utilized to introduce the coherent coupling between qubits for entangling gates. In recent work we demonstrated microwave near-field control of the qubit states, i.e. single-qubit and entangling two-qubit gates. In this experiment laser light is used only for Doppler cooling, state preparation and state detection, significantly reducing laser power and laser control requirements. Recent experiments on this technique will be reported. In addition we will summarize efforts and progress on benchmarking the fidelity of one- and two-qubit gates, ion transport in multi-zone traps, engineering of Ising-spin interaction with a few hundred ion qubits in a Penning trap, investigations of anomalous heating, and quantum limited metrology. *work supported by IARPA, NSA, ONR, DARPA and the NIST Quantum Information Program.

9:00am-9:30amKenton Brown, Georgia Tech Research Institute
Trapped-Ion Physics at GTRI: Towards Large-Scale Integration and Automation

Abstract.

From the earliest days of the field of quantum information, trapped atomic ions have had great potential as qubits. Trapped-ion experiments have demonstrated the individual ingredients believed necessary for scalable quantum information processing, and, for small numbers of ions, many of these ingredients have been combined within the same experimental system. Scaling the capabilities of such test-bed systems to larger numbers of qubits will require a higher level of integration between traps, electronics, optics, and control systems than has been achieved to date. Moreover, calibrating and controlling such a complex system with the necessary speed and accuracy will demand a far greater degree of automation than could be achieved through human intervention.

To explore these challenges, the Quantum Information Systems Group at GTRI has microfabricated several ion traps incorporating 40+ control electrodes, including a long linear trap, a trap with a curved mirror microfabricated onto its surface, an X-junction trap, and a trap with integrated microwave lines. In the linear traps we have loaded long chains with more than 20 resolved ions, while the mirror trap enhanced the collection of ion fluorescence by a factor of 1.8. The junction and microwave traps, when fully tested, should allow us to reorder ions into an arbitrary linear configuration and to perform fast qubit rotations, respectively. Successful operation of these traps necessitates accurate and precise modeling of their electromagnetic properties, so we have developed an in-house method-of-moments simulation package, capable of handling millions of elements, which we use to derive an accurate basis set of micromotion compensation potentials. We are planning an experiment to incorporate in-vacuum DAC electronics alongside a trap chip, all mounted on a single compact circuit board within the vacuum chamber. Finally, we have developed a machine language, known as “OPCODEs”, that translates high-level schedules directly into experimental operations for our ion traps. The success of OPCODEs relies on automated calibration and control of trap parameters, accurate modeling of the potentials required for compensation, and automated detection of ion positions. I will present our most recent experimental results in these areas.



9:30am-10:00amHeather Partner, Sandia National Labs / University of New Mexico
Magnetic field gradient effects on a trapped ion frequency standard

Abstract. We are developing a low-power, high-stability miniature atomic frequency standard based on trapped 171Yb+ ions.  The ions are buffer-gas cooled and held in a linear quadrupole trap that is integrated into a sealed 10 cm^3, getter-pumped vacuum package, and interrogated on the 12.6 GHz hyperfine transition. We hope to achieve a long-term fractional frequency stability of 10^-14 with this miniature clock. To achieve this exceptional long-term stability, the sensitivity of the clock frequency to magnetic fields must be minimized. Because the “clock” transition frequency of 171Yb+ depends quadratically on the magnetic field, it is advantageous to operate at a bias field of ~100 mG or below. However, in small-sized ion traps, magnetic field gradients can prevent operation at low fields because of broadening of the clock resonance. This broadening occurs due to the secular motion of the ions in the trap, which in interaction with a spatially varying magnetic field can induce transitions among the Zeeman sublevels of the upper ground state when the Zeeman frequency is close to the secular frequency of the trap, creating a dephasing effect.  Understanding this mechanism for a particular trap geometry as well as taking steps to eliminate background gradients allows us to operate the clock with a much lower bias field in a region below this secular frequency resonance, where we can both minimize broadening and reduce our clock’s sensitivity to magnetic field fluctuations while reducing the overall power required to run the clock.  We have studied these effects in several traps and will discuss these results as well as clock performance. Peter Schwindt, Yuan-Yu Jau, Michael Descour, Lu Fang, Adrian Casias, Ken Wojciechowski, Roy Olsson, Darwin Serkland, Ron Manginell, Matthew Moorman, Robert Boye, John Prestage, Nan Yu, Robert Lutwak, Sheng Chang