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					Spin Control at the Nanoscale
         David Reilly
    (University of Sydney)




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   Electrons: mass, charge, spin


Spin is the only internal degree of freedom of the electron




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2005 Control and detection of single spins
2006 ESR of single electrons
2008 Manipulation of single nuclear spins
The “holy grail”: Quantum Information Processing




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   From electronics to nanoelectronics to quantum engineering

       Moore’s law pushing into nano…

 Interacting quantum systems pushing into micro…




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 GaAs quantum dots as spin qubits




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Sensing single electrons




                  n-1



       i
              tunneling    But how to go from
   V                       sensing charge to sensing
                           Spins?
Detecting Spins

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 Electrons don’t like each other




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 GaAs double quantum dots: 0,1,2, electrons
                                                    QPC charge sensing signal

i QPC             VL             VR
                                           (2,0)




                                                   (1,0)   (1,1)
                                      VL
                                               (0,0)               (0,1)   (0,2)




                         (2,1)
          (2,0)                                            VR
  VL
                       (1,1)

        (1,0)

                  VR
Readout: Detecting spin-states electrically

                                                      (2,0)
                                                                     ε
                                            VL

                                                       (1,1)
      Nanoscale systems provide a way of detecting single
      Spins (confinement favours large J-energy)   VR


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Energies of Singlet and T0 triplet
                                          Confinement (nano) in (2,0) favors
(T+ and T- split of by magnetic field).   a singlet ground state, allowing
                                          singlet to charge conversion.
 Spin dephasing probes the Overhauser field



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     (2,0)
VL           ε
             (1,1)
         VR
Small, Cold and Fast: nm, mK, MHz readout, GHz control
Controlling Spins at the Nanoscale for
     Applications in Biomedicine
Clinical MRI is based solely on detecting protons in water
How to detect other nuclei in MRI?




                        3He-   lung imaging (Walsworth Group @ Harvard)
13C   MRI Angiography
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        Technique limited by short spin relaxation times
        associated with liquids

(K. Golman)
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Aptekar, Reilly, Marcus (Harvard)
Do birds have spin qubits?




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 endogenic programming



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