Ultra-low frequency noise external cavity diode laser systems for quantum applications.

We present two distinct ultra-low frequency noise lasers at 729 nm with a fast frequency noise of 30 Hz/Hz, corresponding to a Lorentzian linewidth of 0.1 kHz. The characteristics of both lasers, which are based on different types of laser diodes, are investigated using experimental and theoretical analysis with a focus on identifying the advantages and disadvantages of each type of system.

Photon propagation through dissipative Rydberg media at large input rates.

We study the dissipative propagation of quantized light in interacting Rydberg media under the conditions of electromagnetically induced transparency. Rydberg blockade physics in optically dense atomic media leads to strong dissipative interactions between single photons. The regime of high incoming photon flux constitutes a challenging many-body dissipative problem.

Photon Subtraction by Many-Body Decoherence.

We experimentally and theoretically investigate the scattering of a photonic quantum field from another stored in a strongly interacting atomic Rydberg ensemble. Considering the many-body limit of this problem, we derive an exact solution to the scattering-induced spatial decoherence of multiple stored photons, allowing for a rigorous understanding of the underlying dissipative quantum dynamics. Combined with our experiments, this analysis reveals a correlated coherence-protection process in which the scattering from one excitation can shield all others from spatial decoherence.

Single-Photon Absorber Based on Strongly Interacting Rydberg Atoms.

We report on the realization of a free-space single-photon absorber, which deterministically absorbs exactly one photon from an input pulse. Our scheme is based on the saturation of an optically thick medium by a single photon due to Rydberg blockade. By converting one absorbed input photon into a stationary Rydberg excitation, decoupled from the light field through fast engineered dephasing, we blockade the full atomic cloud and change our optical medium from opaque to transparent.

Enhancement of Rydberg-mediated single-photon nonlinearities by electrically tuned Förster resonances.

Mapping the strong interaction between Rydberg atoms onto single photons via electromagnetically induced transparency enables manipulation of light at the single-photon level and few-photon devices such as all-optical switches and transistors operated by individual photons. Here we demonstrate experimentally that Stark-tuned Förster resonances can substantially increase this effective interaction between individual photons. This technique boosts the gain of a single-photon transistor to over 100, enhances the non-destructive detection of single Rydberg atoms to a fidelity beyond 0.