Figure 1

Experimental setup (cavities $C$, $R_1$, and $R_2$ are cut for clarity). The inset shows the cavity spectrum (dots) and a Lorentzian fit (line) with a 2.0 Hz FWHM.Reuse & Permissions

Figure 2

Probability distributions of the atomic spin phase after (a) 0, (b) 20, and (c) 50 field injections in $C$ (no intermediate QND measurements). The thick red line is a fit to a sum of Gaussian distributions (thin green lines). Resolved peaks are centered at the quantized light shifts, clearly illustrating field energy quantization. The Gaussian fits provide a direct measurement of the photon number probability distributions shown in the insets, together with Poissonian fits (solid lines).Reuse & Permissions

Figure 3

(a) Average photon number $\overline{n}$ in $C$ as a function of the number $N$ of injection pulses (bottom axis). The top axis gives a time scale for the complete sequence, including injection and measurement times. The red squares correspond to the uninhibited field growth, without measurements between injections (statistical error bars for $N<50$ are smaller than the point size). The initial evolution is quadratic. The line is a fit providing a precise calibration of the injection pulse amplitude. The blue dots result from atomic spin tomography performed between injection pulses. The field growth is inhibited by the quantum Zeno effect. The open circles correspond to QND measurements of the photon number using 200 atomic detections at the end of sequences with 20, 50, and 100 injection-measurement cycles. (b) Inhibited field evolution with an expanded vertical scale [blue dots in (a)]. The error bars reflect the statistical noise. The solid and dotted black lines are theoretical predictions (see text). The initial growth is now linear.Reuse & Permissions