Figure 1

(a) Configuration of laser beams used for simultaneous quantum-state preparation and laser cooling. The atomic beam is vertical and all laser beams are in the same horizontal plane. The optical lattice beam is folded and retroreflected on a prism to create a phase-stable 2D optical lattice (see Ref. [28]). It has an incoming polarization which is linear at 45${}^{°}$ with respect to the vertical direction, and subsequent multiple reflections on metallic mirrors introduce some ellipticity. The Zeeman pump beam is linearly polarized in the vertical direction and retroreflected with a mirror. It makes a small angle of approximately 5${}^{°}$ with the lattice incoming direction. In principle this angle does not play any role; its value is simply restricted by the optical access to the vacuum system. All mirrors are metallic. A vertical magnetic field is used to stabilize the atomic polarization. (b) Frequencies of the laser beams with respect to the cesium $D_2$ line transitions. In order to produce optical pumping toward $|F=3,m=0\rangle$ the optical lattice beam should excite either the $F=4\to F^{\text{'}}=4$ or the $F=4\to F^{\text{'}}=3$ transition, and the Zeeman pump beam should excite the $F=3\to F^{\text{'}}=3$ transition. As explained in the text, both lasers are detuned in order to produce laser cooling simultaneously with state preparation.Reuse & Permissions

Figure 2

(a) Scheme of the experimental setup. One can see the 2D magneto-optical trap (2D-MOT) where the atomic beam is produced, the 3D moving molasses (MM) which cools and launches the atoms at a speed of $4$ m/s, the transverse laser cooling (TLC) which collimates the atomic beam, the quantum-state-preparation (QSP) stage, the depumper (DEP), the microwave cavity (MWC), and finally the fluorescence detection (DET). (b) Scheme of Zeeman sublevel showing how the population distribution of the $F=3$ ground state is measured in two steps: (1) selective microwave excitation followed by (2) detection of atoms in $F=4$. See Sec. 3 for details.Reuse & Permissions

Figure 3

Microwave spectra measured (a) without state preparation and (b) with state preparation. These spectra represent the number of atoms detected in $F=4$ as a function of the microwave frequency. When the microwave is resonant with one Zeeman component ($|3,m\rangle \to |4,m\rangle$), atoms are transferred in $F=4$ and detected. The microwave power is adjusted for each Zeeman component in order to produce two $\pi /2$ pulses. Note that we used identical scales for both graphs to facilitate the comparison.Reuse & Permissions

Figure 4

Measurement of the total fountain flux in $F=3,4$ (solid line) and the flux in $|F=3,m=0\rangle$ (dashed line) as a function of the optical lattice laser frequency. $\Delta {\nu }_{\mathrm{lattice}}$ is the lattice frequency detuning from the $F=4\to F^{\text{'}}=4$ transition of the cesium $D_2$ line. The Zeeman pump laser is tuned on the $F=3\to F^{\text{'}}=3$ transition. The vertical axis is normalized to the total flux obtained without state preparation ${\varphi }_i^{\mathrm{tot}}$. The dotted horizontal lines A, B, and C indicate the total flux levels when the optical lattice laser is on resonance with the three transitions, respectively. Cooling is observed on the blue side of those transitions. See text for details.Reuse & Permissions

Figure 5

Measurement of the $|F=3,m=0\rangle$ fountain flux as a function of the Zeeman pump laser frequency. $\Delta {\nu }_{\mathrm{pump}}$ is the pump laser frequency detuning from the $F=3\to F^{\text{'}}=3$ transition of the cesium $D_2$ line. The pump laser power values are 3 $\mu$W (solid line) and 30 $\mu$W (dashed line). The vertical axis is normalized to the total flux obtained without state preparation ${\varphi }_i^{\mathrm{tot}}$. The horizontal axis is calibrated using a saturated absorption signal obtained from a small fraction of the pump laser.Reuse & Permissions

Figure 6

Evolution of ${\varphi }_{\mathrm{eq}}=2(S/N){}^2$, where $S$ is the detected signal and $N$ its noise spectral density, as a function of the atomic flux. (a) The triangles are measurements of the atoms in $|F=3,m=0\rangle$ obtained without state preparation. The squares are measurements of the atoms in $|F=3,m=0\rangle$ obtained with state preparation. (b) The circles are measurements of the total flux in $F=3$ and $4$. As explained in the text, the fountain is shot-noise limited at low flux and thus allows a calibration of the photodetector signal in atoms$/$s (horizontal axis). On these graphs the shot-noise limit is a line with unit slope. Note that the three points marked by letters A, B, and C were obtained with the maximum total fountain flux.Reuse & Permissions

Figure 7

Principle of Stark-shift-degenerate Raman sideband cooling [26]. Cold atoms are trapped in the potential wells of an optical lattice, their motion is quantized, and $n$ is the vibrational quantum number. Ground-state Zeeman sublevels with $m\ne 0$ are light-shifted by the blue-detuned $\pi$-pumping laser. When degeneracy is reached between $|F=3,m=0,n\rangle$ and $|F=3,m=\pm 1,n-1\rangle$, degenerate Raman sideband transitions can take place (black horizontal arrows), followed by $\pi$ pumping, which closes the cooling cycle. Every cooling cycle removes one vibrational quantum until the atoms reach $|F=3,m=0,n=0\rangle$. See Ref. [26] for more details.Reuse & Permissions

Figure 8

Measurement of the total fountain flux as a function of the Zeeman pump laser frequency. $\Delta {\nu }_{\mathrm{pump}}$ is the pump laser frequency detuning from the $F=3\to F^{\text{'}}=3$ transition of the cesium $D_2$ line. The pump laser power is $3$ $\mu$W. The vertical axis is normalized to the total flux obtained without state preparation ${\varphi }_i^{\mathrm{tot}}$. The horizontal axis is calibrated using a saturated absorption signal obtained from a small fraction of the pump laser.Reuse & Permissions