Shaping Photons, Dressing Spins: Control at the Single-Quantum Level

The time-frequency-entangled photons described in my earlier talk have coherence times that are long enough that they can be resolved using photodetectors and shaped using electro-ptic modulators. As an example of amplitude control, I will discuss an experiment where we 
demonstrated conditional shaping of single-photon wavepackets. As an example of phase control, I will describe an experimental demonstration of spread-spectrum techniques at the single photon level. An important outcome of this is the ability to pick out a single photon of interest from a background of noise photons at the same frequency.

In the second half of my talk I will describe experiments done with NV centers. I will describe an experiment where we used microwave-dressed states to resonantly couple and transfer spin polarization from NV centers to nearby dark spins in the bath. This process is analogous to sympathetic laser cooling known in atomic physics. I will then describe an experiment where we use dynamical decoupling techniques to mitigate bath-induced decoherence. The increased NV spin-coherence time can be used to enhance sensitivity for magnetic-field-sensing applications. I will conclude with a discussion of my future research 
plans.