Strong intracavity and output laser noise reduction via initial atomic coherence

The dynamics of a two-level atom driven by a single laser beam and three-level atom (Lambda configuration) irradiated by two laser beams are studied taking into account of the quantized center-of-mass motion of the atom. It is shown that the trapped atom system under appropriate resonance condition exhibits the large time-scale revivals when the index of the vibrational sideband responsible for the atomic electronic transition is greater than unity. The revival times are shown to be dependent on the initial number of vibrational excitations and the magnitude of the Lamb-Dicke parameter. The sub-Poissonian statistics in vibrational quantum number is observed at certain time intervals. The minimum time of interaction for which the squeezed states of motional quadrature are generated is found to be decreasing with the increase in the Lamb-Dicke parameter.

Nonlinear corrections on electromagnetic fields in vacuum have been expected. In this study, we have theoretically considered nonlinear Maxwell’s equations in a one-dimensional cavity for a classical light and external static electromagnetic fields. A general solution for the electromagnetic corrective components including that of a longitudinal standing wave was derived after a linearization. The main purpose is to give a detailed feature of the previously reported resonant behavior [Shibata, Euro. Phys. J. D 74:215 (2020)], such as the effect of external static fields and the polarization fluctuation. These results favor the development of new and effective method for experiment.Graphic abstract

The interaction of an intense coherent photon beam with free electrons is discussed. The photon beam is treated as a classical external electromagnetic field. The discussion is exact within the approximation of neglecting radiative corrections and the restriction to the case of a plane-wave field or arbitrary spectral composition and polarization properties. The scattering of a single photon out of a monochromatic beam by an isolated free electron is considered in detail. The cross sections corresponding to the scattering of the various harmonics of the incident beam are evaluated. These cross sections display a complicated dependence upon the intensity of the incident beam, at least for very intense beams. It is found that a mass change induced in the electron by the external field shifts the wavelength of the scattered photons by an amount depending on the intensity of the incident beam. Other processes involving free electrons in the final state are also considered briefly, and a discussion of the magnitude of the effects depending upon the intensity is given. Two Appendices are concerned with the electron Green's function and the vacuum-vacuum transformation function in the presence of a plane-wave field. In the course of the discussion of the latter, the problem of the correct definition of the vacuum current is encountered, and it is shown that a very careful procedure is necessary to obtain a covariant result.

We study the adiabatic evolution of a two-level model in the presence of an external classical electric field. The coupling between the quantum model and the classical field is taken in the electric dipole approximation. In this regime, we show the absence of geometric phases in the interacting two-level model in the presence of any periodic real time-dependent classical electric field. We obtain a conservative scalar potential in the calculation of Berry's phases of the instantaneous eigenstates of the model. For complex electric fields, we recover the existence of geometric phases. In particular, the geometric phases of the instantaneous eigenstates of the model in the presence of a positive or of a negative frequency component of the monochromatic electric field differ by an overall sign. As a check on our results, we map this interacting two-level model onto a spin-1/2 model under the action of a classical magnetic field. We confirm that the first one acquires Berry's phase only in the rotating wave approximation [RWA].

In this paper, we study the effect of detuning parameters and driven external classical field parameters on a quantum system consisting of a ♢-configuration four-level atom inside a quantized cavity field. Under some canonical conditional of dressed states, the exact solution of the Schrödinger equation is obtained. The occupation of atomic levels and statistical population inversion is studied. Our results show that the classical field parameter dissolved the collapse periods and increased the maximum bounds of the upper state, while decreasing the lower bounds of the lower state. The detuning parameters reduce the minimum bounds of atomic levels and their inversion. On the other hand, the linear entropy and l1 norm of coherence are employed to measure the temporal evolution of the mixedness and coherence. It is found that the driven classical field improves the temporal evolution of the mixedness and lower bounds of coherence. However, the detuning parameters have a destructive effect on the mixedness and lower bounds of coherence. The intensity of the external classical field is regarded as a control parameter with different values of detuning parameters.

The interaction of an atomic ensemble localized in a microcavity with external electromagnetic fields under Raman resonance conditions with an optically forbidden atomic transition involving photons of the microcavity mode has been described in terms of third-order polynomial algebra. It has been shown that atoms and photons localized in the microcavity under these conditions form a united object, an atom-photon cluster, on the states of which the irreducible representations of polynomial algebra are implemented. Classical coherent and quantum broadband electromagnetic fields are considered as external fields. The effective Hamiltonian, effective dipole moment operator, and relaxation operator of the atom-photon cluster are expressed in terms of the generators of polynomial algebra, which is the algebra of the dynamical symmetry of the problem. The developed mathematical technique has been applied to describe the main radiative processes—spontaneous emission and nutation effect—on atom-photon clusters. All of these effects are peculiar and differ from similar phenomena on two-level atoms, but only simple cases of the mentioned radiative processes have been considered.

We propose an efficient single-photon router comprising two resonator waveguide channels coupled by several sequential cavities with embedded three-level atoms. We show that the system can operate as a perfect four-way single-photon switch. We also demonstrate that an incident single photon propagating in one of the waveguides can be routed into one or the other output channels; such routing can be controlled by the external classical electromagnetic field driving the atoms. We argue that, under appropriate conditions, the efficiency of such routing can be close to 100% within a broad operational bandwidth, suggesting various applications in photonics.

A coherent trapping phenomenon for the level population of a three-level atom, which takes place on two-photon resonance, has been noted and well studied by a semi-classical approach where the classical electro-magnetic fields are regarded as given [1]. In this article we deal with a closed system of one or two quantized field modes and a three-level (∧-type) atom interacting to each other via the non-vanishing atomic dipole matrix elements d12 and d23 (see Fig. 1). We show that the condition for the coherent trapping determines not only the atomic state but also the field state for the two mode case. In the two mode case (see Fig. 1A), mode l (left) couples with the atom by d12 and mode r (right) by d23. The one mode case with its frequency can be regarded as a special case of the two modes with ωl = ωr = ω (see Fig. 1 B).

In this work, we investigate subluminal and superluminal light propagation in a vee-type three-level atomic medium under an external magnetic field. The dispersion and absorption behaviors are studied for the cases of absence and presence of a magnetic field. It is found that under an electromagnetically induced transparency condition, the light pulse can be switched between subluminal and superluminal propagation by ON-OFF switching of the magnetic field. Finally, the transient response of the medium is discussed, which shows that the considered scheme has potential applications in magneto-optic switching devices. Full Text: PDF ReferencesBoller K J, Imamoglu A, Harris S E, "Observation of electromagnetically induced transparency", Phys. Rev. Lett. 66 (1991) 2593. CrossRef Fleischhauer M, Imamoglu A, Marangos J P, "Electromagnetically induced transparency: Optics in coherent media", Rev. Mod. Phys. 77 (2005) 633. CrossRef L.V. Hau, S. E. Harris, Z. Dutton, C.H. Bejroozi, "Light speed reduction to 17 metres per second in an ultracold atomic gas", Nature, 397 (1999) 594. CrossRef Z. Dutton, N.G.C. Slowe, L.V. Hau, "The art of taming light: ultra-slow and stopped light", Europhysics News, 35 (2004) 33. CrossRef V. Bharti, V. Natarajan, "Sub- and super-luminal light propagation using a Rydberg state", Opt. Commun. 392 (2017) 180-184. CrossRef Khoa D X, Doai L V, Son D H and Bang N H, "Enhancement of self-Kerr nonlinearity via electromagnetically induced transparency in a five-level cascade system: an analytical approach", J. Opt. Soc. Am. B. 31 (2014) 1330. CrossRef Hamedi H R, Gharamaleki A H, and Sahrai M, "Colossal Kerr nonlinearity based on electromagnetically induced transparency in a five-level double-ladder atomic system", Appl. Opt 22 (2016) 5892. CrossRef A. Fountoulakis, A.F. Terzis, E. Paspalakis, "All-optical modulation based on electromagnetically induced transparency", Phys. Lett. A 374, (2010) 3354. CrossRef Khoa D X, Doai L V, Mai Anh L. N, Trung L. C, Thuan P. V, Dung N. T, and Bang N. H, J. "Optical bistability in a five-level cascade EIT medium: an analytical approach", Opt. Soc. Am. B, 33 (2016) 735. CrossRef Hoang Minh Dong, and Nguyen Huy Bang, "Controllable optical switching in a closed-loop three-level lambda system", Phy. Scr. 94, (2019) 115510. CrossRef Dong H M, Doai L V, Sau V N, Khoa D X and Bang N H, "Propagation of a laser pulse in a three-level cascade atomic medium under conditions of electromagnetically induced transparency", Photonics Letter of Poland, 3 (2016) 73. CrossRef Khoa D X, Dong H M, Doai L V and Bang N H, "Propagation of laser pulse in a three-level cascade inhomogeneously broadened medium under electromagnetically induced transparency conditions", Optik 131 (2017) 497. CrossRef H. M. Dong, L.V. Doai, and N.H. Bang, "Pulse propagation in an atomic medium under spontaneously generated coherence, incoherent pumping, and relative laser phase", Opt. Commun. 426 (2018) 553-557. CrossRef Jiahua Li, Rong Yu, Liugang Si, and Xiaoxue Yang, "Propagation of twin light pulses under magneto-optical switching operations in a four-level inverted-Y atomic medium", J. Phys. B: At. Mol. Opt. Phys. 43 (2010) 065502. CrossRef S. H. Asadpour, H. R. Soleimani, "Polarization dependence of optical bistability in the presence of external magnetic field", Opt. Commun 310 (2014) 120-124. CrossRef H.M. Dong, L.T.Y. Nga, and N.H. Bang, "Optical switching and bistability in a degenerated two-level atomic medium under an external magnetic field", App. Opt. 58, (2019) 4192. CrossRef H. M. Dong, L. T. Y. Nga, D. X. Khoa, N. H. Bang, "Controllable ultraslow optical solitons in a degenerated two-level atomic medium under EIT assisted by a magnetic field", Sci. Rep. 10 (2020) 15298. CrossRef Daniel A. Steck, "Rubidium 87D Line Data," http://steck.us/alkalidata. CrossRef

A pure indirect control of quantum systems via a quantum accessor is investigated. In this control scheme, we do not apply any external classical excitation fields on the controlled system and we control a quantum system via a quantum accessor and classical control fields control the accessor only. Complete controllability is investigated for arbitrary finite-dimensional quantum systems and exemplified by two- and three-dimensional systems. The scheme exhibits some advantages; it uses less qubits in the accessor and does not depend on the energy-level structure of the controlled system.

It is shown that a well-defined expression for the total electromagnetic force $f^{em}$ on a point charge source of the classical electromagnetic field can be extracted from the postulate of total momentum conservation whenever the classical electromagnetic field theory satisfies a handful of regularity conditions. Amongst these is the generic local integrability of the field momentum density over a neighborhood of the point charge. This disqualifies the textbook Maxwell-Lorentz field equations, while the Maxwell-Bopp-Lande-Thomas-Podolsky field equations qualify, and presumably so do the Maxwell-Born-Infeld field equations. Most importantly, when the usual relativistic relation between the velocity and the momentum of a point charge with bare rest mass $m_b \neq 0$ is postulated, Newton's law $\dot{p} = f$ with $f = f^{em}$ becomes an integral equation for the point particle's acceleration; the infamous third-order time derivative of the position which plagues the Abraham-Lorentz-Dirac equation of motion does not show up. No infinite bare mass renormalization is invoked, and no ad hoc averaging of fields over a neighborhood of the point charge. The approach lays the rigorous microscopic foundations of classical electrodynamics.

Pronounced anomalies are predicted in the absorption and scattering of electromagnetic and acoustic waves by tunneling particles in local double-well (or multiwell) potentials when an external classical field is applied, ``dressing'' the particles by its numerous excitations. The latter phenomenon, which in particular reflects the previously discovered ``coherent destruction of tunneling,'' gives rise to oscillations of the absorption and scattering coefficients when the classical-field frequency or amplitude is varied, and to their vanishing at certain discrete values of the amplitude-to-frequency ratio. This phenomenon has to occur in some types of defects in crystals, particularly in glasses. For the latter, the dynamical properties at sufficiently low temperatures and frequencies are expected to change basically due to the external classical field.

We present the quantum theory of a two-mode Lambda-type three level quantum-beat laser with injected atomic coherences. The lower two levels are coupled by an external classical field. The master equation and the Fokker–Planck equation are derived. Phases of the two modes are locked to a value depending on the phase of the external field, the phase of the injected coherence and the population of the lower two levels. Lasing without inversion and without threshold is found for both modes with and without injected coherences. Applying the appropriate initial atomic coherences one can switch intensities between the two modes, as well as bifurcation and multiple branching can be found when coherences among all levels are present. It is also possible to find phase bistability at a fixed intensity for one of the two modes, when high pump is applied. Strong intensity and phase noise reduction can be found in one of the modes at the expense of increased noises in the other one. Near Poissonian noise can be achieved. This research was supported by a grant of the Office of Naval Research.

The infrared problem of the effective action in 2D is discussed in the framework of the covariant perturbation theory. The divergences are regularized by a mass and the leading term is evaluated up to the third order of perturbation theory. A summation scheme is proposed which isolates the divergences from the finite part of the series and results in a single term. The latter turns out to be equivalent to the coupling to a certain classical external field. This suggests renormalization by factorization.

The Casimir effect