We use the quantum theory of cascaded open systems to calculate the transmitted photon flux for a weak beam of photons from a cavity QED laser strongly focused onto a single, resonant two-state atom in the narrow-bandwidth limit. We study the dependence of the transmitted flux on the quantum statistics of the incident light. Both bunched and antibunched light generated by the microlaser are considered as input. Working within and outside the semiclassical perturbative regime, we explicitly demonstrate that the normalized transmitted photon flux may coincide with the second-order correlation function of the incident bunched light, but not for incident antibunched light both of which are generated by a cavity QED laser. Interestingly, the thresholdless cavity QED laser is ideal for investigating statistical saturation effects by virtue of its small system size and the large quantum fluctuations accompanying it. It has the advantage of characterizing to a certain extent the quantum noise responsible for the statistical saturation. One can also easily vary the degree of antibunching of the incident light by manipulating the pumping rate of the laser.
We use the quantum theory of cascaded open systems to calculate the transmitted photon flux for a weak beam of photons from a cavity QED laser strongly focused onto a single, resonant two-state atom in the narrow-bandwidth limit. We study the dependence of the transmitted flux on the quantum statistics of the incident light. Both bunched and antibunched light generated by the microlaser are considered as input. Working within and outside the semiclassical perturbative regime, we explicitly demonstrate that the normalized transmitted photon flux may coincide with the second-order correlation function of the incident bunched light, but not for incident antibunched light both of which are generated by a cavity QED laser. Interestingly, the thresholdless cavity QED laser is ideal for investigating statistical saturation effects by virtue of its small system size and the large quantum fluctuations accompanying it. It has the advantage of characterizing to a certain extent the quantum noise responsible for the statistical saturation. One can also easily vary the degree of antibunching of the incident light by manipulating the pumping rate of the laser.
We use the theory of cascaded open systems to calculate the transmitted photon flux for a weak beam of photons focused onto a single, resonant two-state atom in the narrow-bandwidth limit. We study the dependence of the transmitted flux on the quantum statistics of the incident light. Sources of coherent, chaotic, squeezed, antibunched chaotic, and antibunched coherent light are considered. We find that the second-order correlation function and frequency dependence in the wings of the spectrum of the incident light must be considered to explain the results.
Under usual laboratory conditions the absorption of a beam of light by a dilute two-level medium depends on the intensity and spectrum of the incident light. If the incident photon flux is small compared to the decay rate of the absorber’s excited state, saturation effects can be neglected and only the spectrum of the light is important; thus, weak-field absorption depends only on the firstorder correlation function of the incident light. This result relies, however, on a requirement that the incident beam cross-section be much larger than the absorption cross-section of an atom. Then individual atoms act as low efficiency scatterers and the statistics of the scattering process is governed by the law of large numbers applied to many scattering sites. In contrast, if it is arranged that just one atom significantly absorbs (scatters) a beam of photons, correlation functions of the incident light beyond the first-order must be considered. For a beam that is focused within an absorption cross-section, we might naively predict that every photon will be scattered and none transmitted. In fact, even for a very weak beam there is a finite probability for two photons to arrive at the atom within the excited state lifetime, and in this event at least one of them will be transmitted (statistical saturation). In this paper we calculate the transmitted photon flux for a weak beam of photons focussed strongly onto a single, resonant two-state atom. We study the dependence of the transmitted flux on the statistics of the incident photons. Photon beams derived from sources of coherent, chaotic, squeezed, coherent-antibunched, and broadband-antibunched light are considered. our calculations are based on a recently developed theory of cascaded open systems,1,2 and serve to illustrate the usefulness of this theory.
We present analytic results for the photon statistics of a weakly driven optical cavity containing N two-level atoms. The second-order intensity correlation function g(2)() is calculated in the weak field limit for arbitrary atomic and cavity loss rates, and cavity and atomic detunings are included. The transmitted light field may exhibit photon antibunching, sub-Poissonian photon statistics, and other novel nonclassical effects.1,2 The size of these effects depends principally on the single-atom coupling constant C1 = g2/κγ, so these effects persist with many atoms in the cavity. Our results can be interpreted via the collapse of the wave function and quantum interference of probability amplitudes. These phenomena can also be understood in terms of the self-homodyning of the driving field with squeezed polarization fluctuations.2
We investigate theoretically the model of a cavity-quantum-electrodynamics (QED) system that consists of two two-level atoms coupled to a single-mode cavity in the weak coupling regime, where the system is driven by quantum light. The dynamics behavior of the entire system is tackled in the framework of a cascaded quantum system. We find that the two-photon blockade with two-photon bunching and three-photon antibunching can be obtained even when the strong system dissipation is included. This result shows that our work has potential for realizing entangled photon pairs in a weakly coupled cavity. Moreover, we also analyze the photon statistics of the system in the case of out-of-resonance coupling between cavity and two nonidentical atoms. Here, an unconventional photon blockade effect with suppression of two-photon correlation and enhancement of three-photon correlation can be realized, which shows many quantum statistical characteristics of a cavity QED system in weak coupling.
We consider an optical cavity containing a single two-level atom driven on resonance by an external laser source.1 We focus on the limit of weak excitation where the dynamic response of this system is governed by just three parameters: the atom-field coupling constant g, spontaneous emission rate γ for the atom, and cavity decay rate κ. The statistics of the transmitted light are analyzed as a function of g, γ, and κ, in terms of the second-order correlation function g(2)(τ), and the quadrature variances measured in a homodyne detection scheme. Squeezing and photon antibunching exist over a wide range of parameters. For γ ~ κ, the system can exhibit an oscillatory response, even when the mean intracavity photon number is much less than unity.2 The oscillations can be understood in terms of the coupling between the free atom-field eigenstates |0,−>, |0,+>, and |1,−>. The oscillation frequency is determined by the energy level splitting produced between the degenerate one-quantum states |0,+> and |1,−> by the atom-field interaction. The second-order correlation function can exhibit a novel nonclassical effect, where, for g(2)(0) ≠ 0, at some finite delay τ0, the correlation function dips exactly to zero—g(2)(τ0) = 0.
We characterize via the second-order correlation function the quantum correlations in the transmitted light in a two-cascaded-cavities system side-coupled to a common waveguide via bidirectional propagation. Adopting a full quantum master equation and standard input-output theory, we calculate the zero-time-delay second-order correlation function and identify clearly distinguished parameter regimes with the photon bunching and antibunching. Our numerical results clearly show that strong photon antibunching can be achieved in the cascaded double-cavity system without the need for extra modal-overlap-based coupling between the two cavities. Remarkably, this strong photon antibunching appears in the weak-coupling regime of cavity quantum electrodynamics. The photon antibunching properties can be manipulated by adjusting the propagation phase. In addition, we discuss the influences of the emitter-to-cavity coupling strength and the waveguide-to-cavity coupling rate on the photon antibunching. Also, the experimental feasibility of our proposal with the current photonic crystal technique is analyzed. This study offers an alternative way to generate the strongly antibunched photons, which may have applications in on-chip quantum information processing.