Fast Excitation and Photon Emission of a Single-Atom-Cavity System

We report on the fast excitation of a single atom coupled to an optical cavity using laser pulses that are much shorter than all other relevant processes. The cavity frequency constitutes a control parameter that allows the creation of single photons in a superposition of two tunable frequencies. Each photon emitted from the cavity thus exhibits a pronounced amplitude modulation determined by the oscillatory energy exchange between the atom and the cavity. Our technique constitutes a versatile tool for future quantum networking experiments.

Figure 1

(a) ${}^{87}\mathrm{Rb}$ atoms are trapped within the ${\mathrm{TEM}}_{00}$ mode of the cavity at the intersection of a standing-wave dipole trap ($\lambda =1064\mathrm{nm}$) and an intracavity dipole trap ($\lambda =785\mathrm{nm}$, also used for stabilizing the cavity length). Two resonant beams at $\pm 45°$ to the standing-wave trap and perpendicular to the cavity axis provide cooling and fast pulse excitation. The cavity output is coupled to an optical fiber and guided to the detection setup. SPCM: single-photon counting module, NPBS: nonpolarizing beam splitter, $\lambda /4$: quarter-wave plate, EOM: electro-optic modulator, MOT: magneto-optical trap. (b) Measured cavity output photon stream of a single atom with constant laser cooling. The standing-wave trap is turned on at $t=0$ with two atoms trapped during the first 300 ms.

Figure 2

Histogram: normalized arrival time distribution of photons emitted from the trapped atom-cavity system as a function of time after the excitation pulse. Solid closed curve: measured shape of the excitation pulse. Dotted line: exponential decay of the photon emission for an atom in free-space. Inset: Schematic of the atom-cavity system, excitation pulse, and an emitted single photon.

Figure 3

Measured arrival time distribution (dots) of photons emitted from the cavity for different atom-cavity detunings ${\Delta }_{\mathrm{ac}}$. The solid lines are numerical fits (see text).

Figure 4

Measured oscillation frequency of the emitted photons (dots) as a function of ${\Delta }_{\mathrm{ac}}$. The solid line shows the generalized Rabi frequency as a function of detuning from Eq. (2). Inset: Normal modes of the coupled atom-cavity system.

Figure 5

Measured photon arrival time distribution for excitation of the cavity with no atoms (closed dots) and $\lesssim 1$ atom (histogram). The inset compares the temporal evolution of state $|g,1⟩$ for transverse pumping (solid line) with that of $|e,0⟩$ for cavity pumping (dashed line), illustrating the complementary dynamics.