Continuous and Pulsed Quantum Zeno Effect

Continuous and pulsed quantum Zeno effects were observed using a ${}^{87}\mathrm{Rb}$ Bose-Einstein condensate. Oscillations between two ground hyperfine states of a magnetically trapped condensate, externally driven at a transition rate ${\omega }_R$, were suppressed by destructively measuring the population in one of the states with resonant light. The suppression of the transition rate in the two-level system was quantified for pulsed measurements with a time interval $\delta t$ between pulses and continuous measurements with a scattering rate $\gamma$. We observe that the continuous measurements exhibit the same suppression in the transition rate as the pulsed measurements when $\gamma \delta t=3.60(0.43)$, in agreement with the predicted value of 4. Increasing the measurement rate suppressed the transition rate down to $0.005{\omega }_R$.