Time-asymmetric quantum fluctuations in intensity-amplitude correlation for a driven cavity QED system

Abstract

The intensity-amplitude correlation functions for a driven cavity QED system with two non-identical atoms are investigated in this paper. With the support of conditional homodyne detection, one can detect the time-dependent intensity-amplitude correlation functions experimentally. We find time-asymmetry in this correlation when the driving field is tuned to be resonant with the two-photon excitation state, which brings non-Gaussian fluctuations. The physical origin of these phenomena is the distinction of the third-order moment based on complete-collapse and partial-collapse, which corresponds to the measuring sequence of the intensity and amplitude. Finally, we also examined the nonclassical features of the system, which always exhibits photon bunching. The squeezing occurs in the region of weak driving and disappears with the increase of driving strength. Hence, a new classical inequality based on the technique of homodyne cross-correlation measurement is introduced to determine the nonclassicality of the non-Gaussian system in the region of unsqueezing.

Ultranarrow spectral line of the radiation in double qubit-cavity ultrastrong coupling system

“…In summary, the non-Gaussian character of the output field increases with the increase of the driving strength and coupling strength, which is reflected in the CHD signals. Compared with the previous work in the atom-cavity weak coupling system [59], we observe the enhancement of the third-order fluctuations reflecting non-Gaussian and the heighten of amplitude of the entire intensity-amplitude correlation in the qubit-cavity ultrastrong coupling system. This finding is beneficial to the application of the circuit QED system in the experiment of preparation for non-Gaussian light field.…”

“…Finally, we examine the intensity-amplitude correlation of the output field from the circuit QED system. Compared with our previous work based on atomtic system [59], we find that due to the increase of the third-order term representing the non-Gaussian feature of the output light, the intensity-amplitude correlation function of the superconducting qubits system under USC shows a more obvious violation of the classical inequality. This finding is conducive for us to applying this system to the study of nonlinear optics and the preparation of non-classical states.…”

Phase-dependent fluctuations of resonance fluorescence near the coherent population trapping condition

“…asymmetry was readily observed for cavity QED systems both numerically [14,19] and experimentally [15], it has been the resonance fluorescence of several 3LA systems that have provided clear theoretical access to the understanding of the asymmetry [21][22][23][24][25][26]. More recent accounts of asymmetric correlations are found in plasmonics [27] and collective cavity QED [28].…”

“…Since in CHD the signal is time-asymmetric, carrying different information for positive and negative intervals, the spectra of quadratures measured from the amplitudeintensity correlation should be calculated separately [22]: (28) for positive and negative time intervals, respectively. The prefactor γ a α ee is the photon emission rate in the probe transition.…”

Phase-dependent fluctuations of resonance fluorescence near the coherent population trapping condition

“…While this asymmetry was readily observed for cavity QED systems both numerically [14,19] and experimentally [15], it has been the resonance fluorescence of several 3LA systems that have provided clear theoretical access to the understanding of the asymmetry [21][22][23][24][25][26]. More recent accounts of asymmetric correlations are found in plasmonics [27] and collective cavity QED [28].…”