Physics Department, Harvard University - PDF document

Physics Department, Harvard University L.Childress, M.GurudevDutt, J.Taylor,, L.Jiang,A.Zibrov(Harvard)A.Sorensen (NielsBohr Institute)F.Jelezko, J.Wrachtrup(Stuttgart) QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture. Scanning confocalmicroscope image ~100,000 cts/sec(Paris, Munich,..) 20 m copper wireMW Permanent magnet 3-axis Hall sensor oil immersion Dichroic 532 nm fluorescence APD APD Experimental probing of single centers Preparation and probing of single spins 0 1 1 e0 e1 e1 S Phonon emission �Electron spins polarization (90%) Detection using spin-dependent fluorescence 2.88 GHz Contrast limited by competition of optical pumping and shelving effects (improves with efficient collection)Calibrates measurement efficiency for other data First experiments F.Jelezko, J.Wrachtrup(Stuttgart) Rabi oscillationsof single electron spin 8 MHz MW detuning“Beating” of modulation components Single spin coherence via Ramsey spectroscopy “Classic” probe of coherence properties Signatures of complex, non-Markovianenvironment: can we understand, control it? Mesoscopicenvironment of NV center Stiff, mostly spinless 12 C lattice Possible contributors to dephasing: • Contact hyperfine interaction: single N nuclear spin (I=1) • Coupling to remote spins, e.g.: C 13 nuclear spins (few percent) N (impurity) electron spins: need pure samples N Theory: mesoscopic s pin bath effective “nuclear” field local (N) non-local nuc Probing single electron coherence via spin echo…results in much longer coherence BnucSx Typical echo decay … a tool to understand the dynamics of the local environment E.Hahn 1950s The spin echo signal is only sensitive to changes in happen faster than Coherent dynamics involving individual nuclear spins L. Childress, M.G.Dutt, Fast hyperfine modulationLarmorenvelope Coupling to proximal 13C: nuclei-resolving microscope Echo modulation frequencies for different centers Fast component•level mixing and enhancement depend on relative distance Confirms the model 13C …and B-field orientation relative to S-I axis! Coherent, deterministic coupling to isolated single nuclear spins in diamond lattice Addressing of well-defined, isolated nuclear spins possible (up to 3) Coherent, controllable two-qubit(or few qubit!) system L. Childress, M.G.Dutt, J.Taylor, A.Zibrov, F.Jelezko, J.Wrachtrup, P.Hemmer and M.D.L, Science, in press (2006) Theory S I(j) Watching single nuclear spin precession Pulse sequence to map qubitsbetw MW j j polarize polarize measure nuclear polarization Larmorprecession mapping to electron M.GurudevDutt. L.Childress et al Larmordelay ( •NMR on single, isolated nuclear spin! Nuclear spin as robust quantum memory Isolated nuclear qubit: potential for excellent quantum memory Second long coherence times are expected for isolated nuclear spins! How well is13C really isolated (e.g. from nearby electron)? Example: cycling electron with green light during nuclear precession 0.80.6012green pulse duration, sprecession amplitudePreliminary dataB = 20 Gauss34�200 photonsscattered