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Spin Readout with Superconducting Circuits

Spin Readout with Superconducting Circuits. April 27 th , 2011 N. Antler R. Vijay, E. Levenson -Falk, I. Siddiqi. Motivation. Nanobridge SQUID Magnetometer: Spin Physics: Dynamics Coherence times w/ conc. Spin-Substrate Interaction Applications: Nanoscale ESR/NMR. Bi in Si-28.

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Spin Readout with Superconducting Circuits

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  1. Spin Readout with Superconducting Circuits April 27th, 2011 N. Antler R. Vijay, E. Levenson-Falk, I. Siddiqi

  2. Motivation NanobridgeSQUID Magnetometer: • Spin Physics: • Dynamics • Coherence times w/ conc. • Spin-Substrate Interaction • Applications: • Nanoscale ESR/NMR Bi in Si-28 NV Centers in Diamond Cr7Ni (S=1/2)

  3. What is a SQUID? Superconducting QUantum Interference Device

  4. S S I ()  Josephson Junctions LJ and I0 relation is more complex. Insulator (tunnel junction) Constriction (nanobridge junction)

  5. DC SQUID Loop interrupted by two Josephson Junctions. SQUID transduces magnetic flux to phase modulation. IC (Φ)  LJ (Φ) Tunnel Junction DC SQUID LJ >> LLOOP F F o 1 2 3

  6. Flux Transduction Resonator Phase Non-linear Resonator

  7. Readout Scheme

  8. Microwave and Cryogenic Setup

  9. Detector Sensitivity • Low flux noise: • 0.03 μΦ0/Hz1/2 • Bandwidth > 10 MHz • Ideal for “single” spin magnetometry

  10. Bulk Spin Sensitivity Implanted Spins: • 104 Bi atoms/μm2 at 40 nm peak depth Φloop(DC) ~ 27 μΦ0 SNR ~ 3.4 • 100 KHz bandwidth (10μs integration time) • Bulk NV Centers: • Plane of 5.5x1016NV Centers/cm^3, 1 μm above • Φloop(DC) ~ 7 μΦ0 • SNR ~ 1

  11. Single Bohr Magneton Sensitivity • Single Spin Sensitivity: • 180 nm at 1 Hz BW • 2 nm at 10 kHz BW D = 1 to 103nm L = 1 μm

  12. Conclusion • Nanobridge SQUIDs are a good candidate for detecting small #s of spins Next Steps: • Continue looking for signature of spins • Vary spin density and measure relaxation times • Attempt pulsed excitation and control

  13. References • R. Vijay, E. M. Levenson-Falk, D. H. Slichter, and I. Siddiqi, Approaching ideal weak link behavior with three dimensional aluminum nanobridges, Applied Physics Letters 96(22), 223112 (2010) • M. Hatridge, R. Vijay, D. H. Slichter, J. Clarke, and I. Siddiqi, Dispersive magnetometry with a quantum limited SQUID parametric amplifier, Phys. Rev. B 83(13), 134501 (Apr 2011). • R. Vijay, E. Levenson-Falk, N. Antler, and I. Siddiqi, in preparation (2011)

  14. Acknowledgements • Many thanks to all the members of QN • This work supported by: NSF Center for E3S, NSF GRFPand NDSEG

  15. Parametric Amplifier • Drive the resonator such that it is just below the regime where it bifurcates. • Transduction of flux + parametric amplification!

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