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Ion-trap quantum computation Summer School of CQIQC 2012

Ion-trap quantum computation Summer School of CQIQC 2012. Laser Lab Prof. Vasant Natarajan Department of Physics Indian Institute of Science Bangalore. May 25, 2012. Paul trap – dynamic stabilization. Mathieu equation. Mechanical analogue of the stabilization – from Paul’s Nobel lecture.

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Ion-trap quantum computation Summer School of CQIQC 2012

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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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