1. Multiphoton coherent driving in harmonic and non-harmonic spin systems Irinel Chiorescu- Dept of Physics FSU & NHMFL

3. www.physics.fsu.edu Graduate Program! www.physics.fsu.edu Tallahassee, FL

4. Collaborators postdoc: Sylvain Bertaina (moving to CNRS-Marseille, France) grad students: Nick Groll, Lei Chen Prof. Naresh Dalal The EPR group at NHMFL Dr. J. van Tol Dr. S. Nellutla Dept. of Chemistry, Florida State Univ. Dept of Physics, Michigan State University Prof. M. Dykman Funding: NSF-Career, DARPA, NHMFL, Alfred P. Sloan Foundation

5. Spin coherence with Mn spins Mn diluted in MgO single crystal Spin Hamiltonian H = a/6 [S x 4 +S y 4 +S z 4 - S(S+1)(3S 2 -1)/5] +g  B H 0 ·S-AS·I g = 2.0025, a = 55.7 MHz, A = 244 MHz, S = I = 5/2

6. Room Temperature Spectroscopy Data At low power, for a given m I, one see mostly the central resonance -1/2  1/2 Spin levels, fixed m I : anisotropy  non-harmonic -5/2 5/2 -3/2 -1/2 3/2 1/2  m I =0, |  m S |=1

7. Continuous wave multiphoton spectroscopy H 0 || [110], m I =-3/2

8. Room temperature Rabi oscillations EPR measurement of by Free Induction Decay method Rabi frequency ~21 MHz Rabi decay time ~200 ns m I =-5/2, H 0 || [100]

9. Multi-photon/multi-level spin control Calculated dressed states diagrams. The level splittings give the Rabi frequency corresponding to each multi-photon coherent qubit nutation. Rabi oscillations showing as a function of MW pulse length for different MW powers. H 0 || (1,0.8,1), m I =-3/2 4 2

10. Numerical Simulations S. Bertaina (FSU & CNRS-Marseille, France) Anisotropy and hyperfine terms << Zeeman term: - neglect forbidden transition, that is  m I =0 indeed. - diagonalize H in a given m I subspace  H mI - external field good quantization axis, apply RFA: H mI  static H rot - diagonalize H rot  energy diagram (dressed states picture) - time evolution of the density matrix  time and temperature dependence of (Gaussian profile for the resonance)

11. Effect of anisotropy

12. The compensation angle

13. Non-harmonic  Harmonic hF R 1 = 1/2 g  B h mw  (S(S+1)-S z (S z +1)) Rabi frequency between two consecutive levels, in a multi-level system: S z = -1/2  1/2, for  around 0° Rabi frequency in a two level system: hF R comp = 1/2 g  B h mw F R 1 /F R comp = 53.5 MHz / 18.07 MHz =2.96 At  =  comp : non-harmonic  harmonic multi-level system with a 2-level system dynamics

14. Multi-photon Rabi oscillations T=40K, H 0 || [101] and m I =-3/2

15.  comp at room temperature RT, h mw =0.52 mT: F R 1 /F R comp = 21 MHz / 7 MHz =3 (to be compared with 2.96 at h mw =1.34 mT)