G.T. Foster

Time evolution and squeezing of the field amplitude in cavity QED

Summary form only given. Squeezing has traditionally been measured with a homodyne detector whose photocurrent output is frequency analyzed to quantify the noise reduction below the standard quantum limit. This measurement technique suffers from detection and propagation efficiencies. It seldom permits the complete reconstruction of the spectrum particularly when the frequency range is large. We have developed a new way to measure the squeezing spectrum through a third-order correlation function of the field. We correlate the detection of a photon with the record of the output of the photocurrent from a balanced homodyne detector. This method is a variant of the intensity correlation measurements that have shown non-classical features of the electromagnetic field.

Time response of a coupled atoms-cavity system.

We study the time response of a quantum optical system to a step excitation. The system is composed of a collection of N two-level atoms coupled to a single mode of the electromagnetic field of an optical cavity. The size of the step excitation is not limited to the low-intensity regime. Before the system reaches steady state there is an oscillatory exchange of energy between the atoms and the cavity. We compare the experimental results quantitatively with theoretical calculations and with previous transmission spectroscopy measurements.

Intensity correlations of a noise-driven diode laser

We couple noise into the driving current of a laser diode to produce correlated light. We characterize the intensity correlations of the laser with two different techniques: two-detector photon coincidence and analysis of the photocurrent from a single detector. The light exhibits bunching with a magnitude and characteristic time set by the bandwidth and the amplitude of the noise modulating the laser driving current. A simple model based on amplitude modulation of the laser intensity agrees with the measured correlation functions. The bunched light can be used to probe systems that are sensitive to intensity correlations.

Conditional evolution in cavity QED

Summary form only given. The second order intensity correlation function can provide evidence of the non-classical nature of an electric field, as well as information about the dynamics which produce the field. In practice, this is a conditional measurement of the probability to detect a photon given that another photon was detected in coincidence or some time before. We have measured the correlation function of the photons escaping from a strongly coupled cavity QED system consisting of a high finesse interferometer traversed by a beam of optically pumped Rb atoms. In this regime, the rate of reversible exchange of energy between the atoms and the cavity is larger than the cavity decay and spontaneous emission rates, and the saturation photon number is less than one. The correlations exhibit the non-classical features of antibunching and sub-Poissonian statistics, and an oscillation related to the exchange of energy taking place in the coupled system of atoms and cavity field. We view the initial photon detection as causing a projection of the system into a well defined initial state from which it coherently evolves back to steady state. A full characterization of this conditional evolution requires the measurement of the electric field as it evolves from the initial state.

Correlation measurements in cavity QED: detuning effects

Summary form only given. The second-order correlation function of the intensity is a measurement of the intensity fluctuations and their enhancement or suppression relative to an ideal laser field. It is a sensitive probe of the dynamic processes involved in producing the light. We have measured the correlation function of the photons escaping from a cavity QED system consisting of a high-finesse interferometer traversed by an atomic beam of optically pumped Rb atoms. We observe nonclassical correlations, exhibiting antibunching and sub-Poissonian statistics.