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Advantages of Trapped Ions for Quantum Computation

Explore the Paul trap and its mechanics, Mathieu equation in laser manipulation, and ion-trap quantum computation techniques. Discover the tight confinement, sideband cooling, and life time measurement methods for quantum systems. Details on experimental requirements, trap design, and why Calcium ions are preferred for such applications. Acknowledging the workshop and students involved in furthering quantum computation studies.

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Advantages of Trapped Ions for Quantum Computation

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  1. Ion-trap quantum computationSummer School of CQIQC 2012 Laser Lab Prof. Vasant Natarajan Department of Physics Indian Institute of Science Bangalore May 25, 2012

  2. Paul trap – dynamic stabilization Mathieu equation

  3. Mechanical analogue of the stabilization – from Paul’s Nobel lecture

  4. Mathieu stability plot

  5. Spectrum from harmonically-oscillating particle fm modulation with depth of modulation kx0 Tight confinement – Lamb-Dicke regime x0 << λ

  6. , , , , Sideband cooling | e > | g> Cooling laser tuned to lower motional sideband

  7. Ca+ energy levels Shelving Repumping Cooling

  8. Life time measurement • Shelving technique by Dehmelt observation of quantum jumps to determine the lifetime • Both lasers run continuously and we observe the fluorescence photons at a rate of a few kHZ. • For a time in order of 1 s we apply a third laser at 4P3/2 –3D3/2 transition. • By decay of 4P3/2 level the ion may fall into the metastable 3D5/2 state and the fluorescence vanishes. • Repeat the process and determine the time intervals where no fluorescence is observed after blocking the shelving laser.

  9. Life time measurement Histogram of the dark periods for a single ion. The experimental data are fitted by an exponential

  10. Linear Paul trap design Each section length = 15mm Rod diameter = 6 mm r0 = 2.66 mm For axial trapping additional DC field = 150 V RF between diagonal rods for radial trapping V0 = 100 V ω0 = 2 MHZ UHV= 10-10 torr Ions get trapped in a linear chain on the axis of the trap

  11. Photos of linear ion trap

  12. Experimental requirements • Need three lasers working simultaneously – Cooling (397), Repumping (866), and shelving (850) • Use 397 nm fluorescence from hollow cathode lamp to lock cooling laser • Mix all the beams in a hollow-core fiber and transport them to the experiment • Use an ICCD Camera for detection

  13. Experimental Schematic

  14. Ca+ energy levels Shelving Repumping Cooling

  15. Why Calcium • Has a lambda level scheme with two lying metastable 3D states • Ca+ has a closed shell plus a single valance electron. • No outer correlation exist but core effects play an important role • Electric field of the valence electron causes a core polarization leading to modified nuclear electric field seen by the outermost electron to explore new physics.

  16. Advantages of trapped ions for quantum computation • Near-perfect two level system formed of a ground level and a metastable excited level • Decoupled from the environment and well isolated in vacuum for long storage times • Internal states can be initialized and measured with extremely high accuracy • Laser pulses can be used to manipulate electronic and motional degrees of the ion string

  17. Acknowledgements Workshop – Manohar, Sharief Students – Ayan Banerjee, Dipankar Das, Dipankar Kaundilya, Lal Muanzuala, Durgesh Datar, Zeba Naqvi Money – DST and CQIQC

  18. Sideband Cooling

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