Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Resonance fluorescence from three-level atoms: Atomic coherences and squeezed light

W. Vogel, R. Blatt

Published Mar 1, 1992• 26 citations
Publisher

Abstract

Atomic coherences and squeezing of the resonance fluorescence are investigated for three-level atoms of the \ensuremath{\Lambda} configuration. An experimental scheme is proposed for direct observation of the atomic coherence in the lower states, based on switching the phase difference of the pump lasers. Squeezing of the resonance fluoresence of three-level atoms is predicted even when long-lived atomic coherences exist.

DOI
10.1103/physreva.45.3319

Related papers

Squeezing and trapping in three-level atoms

F. A. M. de Oliveira, Bryan J. Dalton, P. L. Knight

We discuss the phase-sensitive noise properties of fluorescence emitted by three-level atoms coherently excited by two laser fields, using both undressed and dressed uncoupled-state representations. The occurrence of steady-state squeezing is found to be highly sensitive to relaxation processes between the two-photon resonant levels. For purely radiative decay from the upper level, and no lower-state relaxation, the population is susceptible to coherent population trapping. Near two-photon resonance, the atom is optically pumped into a nonabsorbing (trapped) superposition state, which, although it reduces upper-level population, also leads to an interference cancellation of dipole moments and to suppression of squeezing. Lower-level relaxation unbalances this interference and restores the squeezing to some extent. Transient squeezing is also predicted in the time-dependent fluorescence.

Journal of the Optical Society of America B•Oct 1, 1987•31 citations

Atomic coherence effects in a three-level atom

W. Vogel, R. Blatt

A folded three-level system that is excited to resonance fluorescence with two monochromatic lasers exhibits a dark resonance. This phenomenon is usually interpreted as arising from a coherent superposition of two long-lived states1–3. To demonstrate directly such an atomic coherence, we propose intensity correlation measurements of the resonance fluorescence with a phase shift between the laser phases introduced after a certain delay time.

Quantum Electronics and Laser Science Conference•May 12, 1991•0 citations

Three-level Atom in a Squeezed Vacuum II

S. Smart, S. Swain

The resonance fluorescence of a three-level system is studied in each of its three possible configurations—ladder, lambda and vee—when it also interacts with broad band squeezed vacua and the applied fields are resonant. We obtain general expressions which apply for any configuration and do not make use of the secular approximation. Detailed results are presented which depend upon the degree of squeezing and the squeezing phase, in addition to the intensities of the applied fields. It is shown that asymmetric spectra may be obtained in certain circumstances. These are interpreted in terms of coherent and incoherent transitions induced by the squeezed fields. We also take the opportunity to assess the accuracy of the secular approximation.

Journal of Modern Optics•Jun 1, 1994•22 citations

The role of quantum jumps in the squeezing of resonance fluorescence from short-lived and long-lived atoms

Samir Bali

Phase-sensitive squeezing in the resonance fluorescence of two-level atoms, that are coherently driven by a near-resonant laser field in free space, was observed recently (Lu et al 1998 Phys. Rev .L ett. 81 3635). This was accomplished via homodyne detection at a phase near ±45 ◦ relative to the driving field for strong off-resonant excitation of ‘long-lived’ atoms (where th ea tomic lifetime far exceeded the laser–atom interaction time, meaning that relaxation effects could be ignored). On the other hand, traditional theoretical predictions of phase-sensitive squeezing in the resonance fluorescence from two-level atoms have emphasized in- and out-of-phase (i.e., 0 ◦ and 90 ◦ ) quadratures, and weak, on-resonant excitation of ‘short-lived’ atoms (where the observation time for laser–atom interaction fa re xceeded the natural atomic lifetime, meaning that relaxation effects dominate). Here, we calculate the probability of a delayed-coincidence detection in the interference field of a fluorescing dipole with a local oscillator (LO). We show that, despite the strikingly different conditions in which squeezing occurs in short- and long-lived atoms, squeezing in both cases can be shown to arise from a joint detection of two photons which are related by a quantum jump in the following way: the first photodetection precipitates a quantum jump of the atom to the ground state, and the second measures the mean amplitude of the fluorescent field subsequent to the quantum jump.

Journal of Optics B Quantum and Semiclassical Optics•Jul 28, 2004•3 citations

Optimum field squeezing from atomic sources: Three-level atoms

Bryan J. Dalton, Z. Ficek, P. L. Knight

Light emitted from laser-driven atoms often has squeezed quadrature fluctuations reflecting the phase dependence of the atomic source excited into a coherent superposition by the driving field. In this paper, we study the maximum squeezing in the emitted light fields from three-level atoms, paying particular attention to the role of atomic coherences in governing the optimum squeezing which is possible. Some phase dependent nonlinear optical processes have the potential for substantial quantum noise reduction at useful intensities: for example, four-wave mixing involving atomic systems has already been used to generate quadrature-squeezed light. The threoretical description of such a source is generally complicated with damping processes, coherent and incoherent pumping, and so on, all needing to be taken into account. Fully quantum treatments are available, but the basic physics of the process is often difficult to grasp in the necessarily complicated analysis. Although less important from the point of view of efficient practical sources of squeezed light, studying the generation of squeezed light in simpler systems such as two- or three-level atoms interacting with one or two modes (as in Jaynes-Cummings models) or in spontaneous emission or resonance fluorescence gives greater insight into the fundamentals of the squeezing process. In particular, the relationship between the atomic coherences and the degree of squeezing in the generated fields can be explored. We study the maximum (optimized) squeezing that can be obtained in the emitted fields from the irreversible decay from three-level atoms for any choice of initial conditions, excitations and decay process, for all quadrature components and for all possible configurations (V, \ensuremath{\Lambda}, and ``ladder'' systems).We show that for V and \ensuremath{\Lambda} systems, optimum squeezing is actually associated with a two-level state (in a suitable basis) involving a single one-photon coherence, but for ladder systems the state for maximum noise reduction is not equivalent to a two-level system and involves a single two-photon coherence and no intermediate state population. We pay particular attention to whether the total field is in a minimum uncertainty state, and the nature of the atomic state associated with maximum squeezing, especially whether it is a mixed or pure state. In the case where the initial free field has a zero amplitude at the detector and the source atoms are confined to a region small compared to the wavelength (Dicke source) we show that the squeezing in the total field is given in terms of the squeezing in the source field, and hence related to atomic populations and atomic one-photon and two-photon coherences for the case of three level atom. Previously unconsidered source-free field interferences terms are shown to be zero. The choice of quadrature phase and frequency is optimized to minimize the source field normally ordered variance. We then minimize further with respect to the choice of atomic density matrix elements subject to the constraints that the density matrix is Hermitean, positive, and has a trace equal to unity. In all cases we find that the optimum squeezing is produced when the source field is in a minimum uncertainty state.

Physical Review A•Sep 1, 1994•24 citations

Enhancement of steady-state squeezing in the resonance fluorescence of a coherently driven four-level atom of Λ configuration via quantum interference

Fuli Li, Shao-yan Gao, Shi-Yao Zhu

We investigate steady-state squeezing in the phase quadratures of the resonance fluorescence emitted from a coherently driven four-level atom of $\ensuremath{\Lambda}$ configuration. Quantum fluctuation spectra of the optimum-phase quadratures are calculated. We show that if quantum interference between spontaneous emission channels from closed excited states to lower levels of the atom takes place, squeezing in the optimum-phase quadrature can occur in a very wider region of the parameter space than that predicted by previous studies. We also show that the quantum interference can greatly change the atomic coherences and then lead to this interesting result.

Physical Review A•Jun 30, 2003•15 citations
Atomic coherences and squeezing of the resonance fluorescence are investigated for three-level atoms of the \ensuremath{\Lambda} configuration. An experimental scheme is proposed for direct observation of the atomic coherence in the lower states, based on switching the phase difference of the pump lasers. Squeezing of the resonance fluoresence of three-level atoms is predicted even when long-lived atomic coherences exist.
We discuss the phase-sensitive noise properties of fluorescence emitted by three-level atoms coherently excited by two laser fields, using both undressed and dressed uncoupled-state representations. The occurrence of steady-state squeezing is found to be highly sensitive to relaxation processes between the two-photon resonant levels. For purely radiative decay from the upper level, and no lower-state relaxation, the population is susceptible to coherent population trapping. Near two-photon resonance, the atom is optically pumped into a nonabsorbing (trapped) superposition state, which, although it reduces upper-level population, also leads to an interference cancellation of dipole moments and to suppression of squeezing. Lower-level relaxation unbalances this interference and restores the squeezing to some extent. Transient squeezing is also predicted in the time-dependent fluorescence.
The resonance fluorescence of a three-level system is studied in each of its three possible configurations—ladder, lambda and vee—when it also interacts with broad band squeezed vacua and the applied fields are resonant. We obtain general expressions which apply for any configuration and do not make use of the secular approximation. Detailed results are presented which depend upon the degree of squeezing and the squeezing phase, in addition to the intensities of the applied fields. It is shown that asymmetric spectra may be obtained in certain circumstances. These are interpreted in terms of coherent and incoherent transitions induced by the squeezed fields. We also take the opportunity to assess the accuracy of the secular approximation.
Phase-sensitive squeezing in the resonance fluorescence of two-level atoms, that are coherently driven by a near-resonant laser field in free space, was observed recently (Lu et al 1998 Phys. Rev .L ett. 81 3635). This was accomplished via homodyne detection at a phase near ±45 ◦ relative to the driving field for strong off-resonant excitation of ‘long-lived’ atoms (where th ea tomic lifetime far exceeded the laser–atom interaction time, meaning that relaxation effects could be ignored). On the other hand, traditional theoretical predictions of phase-sensitive squeezing in the resonance fluorescence from two-level atoms have emphasized in- and out-of-phase (i.e., 0 ◦ and 90 ◦ ) quadratures, and weak, on-resonant excitation of ‘short-lived’ atoms (where the observation time for laser–atom interaction fa re xceeded the natural atomic lifetime, meaning that relaxation effects dominate). Here, we calculate the probability of a delayed-coincidence detection in the interference field of a fluorescing dipole with a local oscillator (LO). We show that, despite the strikingly different conditions in which squeezing occurs in short- and long-lived atoms, squeezing in both cases can be shown to arise from a joint detection of two photons which are related by a quantum jump in the following way: the first photodetection precipitates a quantum jump of the atom to the ground state, and the second measures the mean amplitude of the fluorescent field subsequent to the quantum jump.
Light emitted from laser-driven atoms often has squeezed quadrature fluctuations reflecting the phase dependence of the atomic source excited into a coherent superposition by the driving field. In this paper, we study the maximum squeezing in the emitted light fields from three-level atoms, paying particular attention to the role of atomic coherences in governing the optimum squeezing which is possible. Some phase dependent nonlinear optical processes have the potential for substantial quantum noise reduction at useful intensities: for example, four-wave mixing involving atomic systems has already been used to generate quadrature-squeezed light. The threoretical description of such a source is generally complicated with damping processes, coherent and incoherent pumping, and so on, all needing to be taken into account. Fully quantum treatments are available, but the basic physics of the process is often difficult to grasp in the necessarily complicated analysis. Although less important from the point of view of efficient practical sources of squeezed light, studying the generation of squeezed light in simpler systems such as two- or three-level atoms interacting with one or two modes (as in Jaynes-Cummings models) or in spontaneous emission or resonance fluorescence gives greater insight into the fundamentals of the squeezing process. In particular, the relationship between the atomic coherences and the degree of squeezing in the generated fields can be explored. We study the maximum (optimized) squeezing that can be obtained in the emitted fields from the irreversible decay from three-level atoms for any choice of initial conditions, excitations and decay process, for all quadrature components and for all possible configurations (V, \ensuremath{\Lambda}, and ``ladder'' systems).We show that for V and \ensuremath{\Lambda} systems, optimum squeezing is actually associated with a two-level state (in a suitable basis) involving a single one-photon coherence, but for ladder systems the state for maximum noise reduction is not equivalent to a two-level system and involves a single two-photon coherence and no intermediate state population. We pay particular attention to whether the total field is in a minimum uncertainty state, and the nature of the atomic state associated with maximum squeezing, especially whether it is a mixed or pure state. In the case where the initial free field has a zero amplitude at the detector and the source atoms are confined to a region small compared to the wavelength (Dicke source) we show that the squeezing in the total field is given in terms of the squeezing in the source field, and hence related to atomic populations and atomic one-photon and two-photon coherences for the case of three level atom. Previously unconsidered source-free field interferences terms are shown to be zero. The choice of quadrature phase and frequency is optimized to minimize the source field normally ordered variance. We then minimize further with respect to the choice of atomic density matrix elements subject to the constraints that the density matrix is Hermitean, positive, and has a trace equal to unity. In all cases we find that the optimum squeezing is produced when the source field is in a minimum uncertainty state.
We investigate steady-state squeezing in the phase quadratures of the resonance fluorescence emitted from a coherently driven four-level atom of $\ensuremath{\Lambda}$ configuration. Quantum fluctuation spectra of the optimum-phase quadratures are calculated. We show that if quantum interference between spontaneous emission channels from closed excited states to lower levels of the atom takes place, squeezing in the optimum-phase quadrature can occur in a very wider region of the parameter space than that predicted by previous studies. We also show that the quantum interference can greatly change the atomic coherences and then lead to this interesting result.