Collecting Photons

National Research Council

Chang-Min Lee, Hee‐Jin Lim, Christian Schneider +4 more

Efficient single photon collection is demonstrated based on a μ-fiber-coupled photonic crystal cavity. 249 kHz of single photons are detected, and estimated single photon count rate(overall collection efficiency) is 20 MHz(25 %).

Joachim Piprek

David Le Sage, Linh Pham, Nir Bar‐Gill +4 more

A common limitation of experiments using color centers in diamond is the poor photon collection efficiency of microscope objectives due to refraction at the diamond interface. We present a simple and effective technique to detect a large fraction of photons emitted by color centers within a planar diamond sample by detecting light that is guided to the edges of the diamond via total internal reflection. We describe a prototype device using this ``side-collection'' technique, which provides a photon collection efficiency $\ensuremath{\approx}47%$ and a photon detection efficiency $\ensuremath{\approx}39%$. We apply the enhanced signal-to-noise ratio gained from side collection to ac magnetometry using ensembles of nitrogen-vacancy (NV) color centers, and demonstrate an ac magnetic field sensitivity $\ensuremath{\approx}100\phantom{\rule{0.28em}{0ex}}\mathrm{pT}/\sqrt{\mathrm{Hz}}$, limited by added noise in the prototype side-collection device. Technical optimization should allow significant further improvements in photon collection and detection efficiency as well as subpicotesla NV-diamond magnetic field sensitivity using the side-collection technique.

Russell Ruthen

Mohammadsadegh Khazali, Khabat Heshami, Christoph Simon

We propose a scheme for a deterministic controlled-phase gate between two photons that is based on the strong interaction between two stationary collective Rydberg excitations in an atomic ensemble outside the regime of Rydberg blockade. The distance-dependent character of the interaction causes both a momentum displacement of the collective excitations and unwanted entanglement between them. We show that these effects can be overcome by swapping the collective excitations in space and by optimizing the geometry, resulting in a photon-photon gate with high fidelity and efficiency.