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Ion-trap quantum computation
Summer School of CQIQC 2012
Laser Lab
Prof. Vasant Natarajan
Department of PhysicsIndian Institute of Science
Bangalore
May 25, 2012
Spectrum from harmonically-oscillating particle
fm modulation with depth of modulation kx0
Tight confinement – Lamb-Dicke regime x0 << λ
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.
Life time measurement
Histogram of the dark periods for a single ion. The experimental data are fitted by an exponential
Linear Paul trap design
Each section length = 15mmRod diameter = 6 mmr0 = 2.66 mm For axial trapping additional DC field = 150 VRF between diagonal rods for radial trapping V0 = 100 Vω0 = 2 MHZUHV= 10-10 torr Ions get trapped in a linear chain on the axis of the trap
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
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.
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
Acknowledgements
Workshop – Manohar, Sharief
Students – Ayan Banerjee, Dipankar Das, Dipankar Kaundilya, Lal Muanzuala, Durgesh Datar, Zeba Naqvi
Money – DST and CQIQC