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

Nonlinear Optics

Controlling quantum fluctuations by electromagnetic field induced coherences

G. S. Agarwal

Published Dec 17, 2002• 0 citations
Publisher

Abstract

It is well established that a /spl Lambda/-system under the action of two intense fields and in the absence of collisions ends up in a state known as coherent population trapping state (CPT state). This state has well defined coherence between the two lower levels of the /spl Lambda/-system and has found many different applications. In this paper I demonstrate the utility of this coherence in controlling quantum fluctuations.>

DOI
10.1109/nlo.1994.470751

Related papers

Coherent Population Trapping Induced by Phase Modulated and Fluctuating Fields

Jian Wang, Xiangming Hu

We examine the effects of cross correlated phase fluctuations on the coherent population trapping (CPT) induced by a pair of phase-modulated fields with equal modulation frequencies in a three-level Λ system. The maximal coherence of -0.5, which appears when CPT occurs for equal modulation indices, is preserved in the presence of the critically cross-correlated fluctuations. Unexpectedly, the non-maximal coherence, which is established when CPT is obtained for different modulation indices, is significantly enhanced due to the critically cross-correlated fluctuations.

Chinese Physics Letters•Jan 18, 2007•2 citations

Coherent population trapping via quantum interference of incoherent pump processes in three-level systems

Xiangming Hu, Jie-Peng Zhang

Quantum interference has been predicted to occur in a three-level Λ system with near-degenerate dipole allowed transitions, which are coupled to the same linearly polarized incoherent field. For the Λ system with two degenerate lower levels, we show that (a) quantum interference of incoherent pump processes leads to coherent population trapping (CPT), and (b) when two coherent fields are applied to two transitions on two-photon resonance, CPT appears when the amplitudes and phases of the applied coherent fields and the polarization angle of the incoherent field satisfy certain conditions. Further, the physical mechanism and the above conditions for CPT are presented.

Journal of Physics B Atomic Molecular and Optical Physics•Dec 17, 2003•19 citations

Effects of spontaneously generated coherence on the pump-probe response of a Λ system

Sunish Menon, G. S. Agarwal

Near-degenerate lower levels in a $\ensuremath{\Lambda}$ system have an additional coherence term due to interaction with the vacuum of the radiation field. We report the effects of this spontaneously generated coherence on the formation of a trapped state in the presence of two coherent fields of arbitrary intensity. We show that such coherence preserves both electromagnetically induced transparency and coherent population trapping (CPT) phenomena. However, it changes the time scales associated with the formation of the CPT state, and brings about quantitative changes in the line profiles. We present a clear analytical explanation for our numerical results. We also report the dependence of line shapes on the relative phase between the two applied fields.

Physical Review A•May 1, 1998•219 citations

Coherent population trapping under periodic polarization modulation: Appearance of the CPT doublet

M. Huang, James C. Camparo

In order to understand how stochastic processes might enter and influence coherent atomic dynamics, we have studied the behavior of a \ensuremath{\Lambda} system under periodic polarization modulation. Polarization, in addition to amplitude and phase, is a defining feature of a classical vector field. However, to date, there has been little study concerning the response of quantum systems to temporal variations in polarization, even though some lasers are known to exhibit stochastic polarization fluctuations. In our work, we square-wave modulate the polarization of a laser that induces coherent-population trapping (CPT) in ${}^{87}$Rb. At low-modulation frequencies, we find that the amplitude of the CPT resonance increases with modulation frequency because the polarization variations limit the number of atoms confined to the system's trapping state. Surprisingly, at higher-modulation frequencies, we find that the CPT resonance splits into a doublet. We have developed an analytical theory of CPT in the presence of polarization modulation that captures the primary features of our experimental findings and shows that the doublet is a consequence of ground-state coherence modulation in the \ensuremath{\Lambda} system. The present results lay a foundation for understanding how more complicated (i.e., stochastic) temporal variations in laser polarization could influence \ensuremath{\Lambda}-system dynamics.

Physical Review A•Jan 12, 2012•20 citations

Coherent population trapping in the Λ system by a two-mode quantized field in an SU(2) coherent state

Christopher C. Gerry

Coherent population trapping (CPT) in a three-level system in the Λ configuration interacting with two quantized fields is studied. It is shown that, in addition to the known trapping states of the field involving ordinary coherent states of each mode, SU(2) coherent states associated with the Schwinger realization are also field states that give rise to CPT for this system. In addition it is pointed out that superpositions of such states, and statistical mixtures of them, for different total photon numbers also give rise to CPT. The stability of the CPT states against decay of the cavity field modes is examined. CPT is preserved if the modes decay at the same rate. A possible method for generating statistical mixtures of the SU(2) coherent states is described.

Journal of Modern Optics•Apr 1, 1999•1 citation

Coherent population trapping at low light levels

Iyyanki V. Jyotsna, G. S. Agarwal

A three-level lambda ($\ensuremath{\Lambda}$) system driven by two coherent fields at the Raman resonance condition evolves to a nonabsorbing eigenstate of the Hamiltonian called the coherent population trapping (CPT) state. We study the various factors dictating the dynamical evolution of the coherences and the populations to the CPT state. We demonstrate the formation of the CPT state even at low intensities, though it takes much longer to form such a state. For the case of unequal decay rates we demonstrate an interesting sharp dip in the steady-state response of the medium at the Raman resonance condition.

Physical Review A•Oct 1, 1995•43 citations
It is well established that a /spl Lambda/-system under the action of two intense fields and in the absence of collisions ends up in a state known as coherent population trapping state (CPT state). This state has well defined coherence between the two lower levels of the /spl Lambda/-system and has found many different applications. In this paper I demonstrate the utility of this coherence in controlling quantum fluctuations.>
We examine the effects of cross correlated phase fluctuations on the coherent population trapping (CPT) induced by a pair of phase-modulated fields with equal modulation frequencies in a three-level Λ system. The maximal coherence of -0.5, which appears when CPT occurs for equal modulation indices, is preserved in the presence of the critically cross-correlated fluctuations. Unexpectedly, the non-maximal coherence, which is established when CPT is obtained for different modulation indices, is significantly enhanced due to the critically cross-correlated fluctuations.
Quantum interference has been predicted to occur in a three-level Λ system with near-degenerate dipole allowed transitions, which are coupled to the same linearly polarized incoherent field. For the Λ system with two degenerate lower levels, we show that (a) quantum interference of incoherent pump processes leads to coherent population trapping (CPT), and (b) when two coherent fields are applied to two transitions on two-photon resonance, CPT appears when the amplitudes and phases of the applied coherent fields and the polarization angle of the incoherent field satisfy certain conditions. Further, the physical mechanism and the above conditions for CPT are presented.
Near-degenerate lower levels in a $\ensuremath{\Lambda}$ system have an additional coherence term due to interaction with the vacuum of the radiation field. We report the effects of this spontaneously generated coherence on the formation of a trapped state in the presence of two coherent fields of arbitrary intensity. We show that such coherence preserves both electromagnetically induced transparency and coherent population trapping (CPT) phenomena. However, it changes the time scales associated with the formation of the CPT state, and brings about quantitative changes in the line profiles. We present a clear analytical explanation for our numerical results. We also report the dependence of line shapes on the relative phase between the two applied fields.
In order to understand how stochastic processes might enter and influence coherent atomic dynamics, we have studied the behavior of a \ensuremath{\Lambda} system under periodic polarization modulation. Polarization, in addition to amplitude and phase, is a defining feature of a classical vector field. However, to date, there has been little study concerning the response of quantum systems to temporal variations in polarization, even though some lasers are known to exhibit stochastic polarization fluctuations. In our work, we square-wave modulate the polarization of a laser that induces coherent-population trapping (CPT) in 87{}^{87}87Rb. At low-modulation frequencies, we find that the amplitude of the CPT resonance increases with modulation frequency because the polarization variations limit the number of atoms confined to the system's trapping state. Surprisingly, at higher-modulation frequencies, we find that the CPT resonance splits into a doublet. We have developed an analytical theory of CPT in the presence of polarization modulation that captures the primary features of our experimental findings and shows that the doublet is a consequence of ground-state coherence modulation in the \ensuremath{\Lambda} system. The present results lay a foundation for understanding how more complicated (i.e., stochastic) temporal variations in laser polarization could influence \ensuremath{\Lambda}-system dynamics.
Coherent population trapping (CPT) in a three-level system in the Λ configuration interacting with two quantized fields is studied. It is shown that, in addition to the known trapping states of the field involving ordinary coherent states of each mode, SU(2) coherent states associated with the Schwinger realization are also field states that give rise to CPT for this system. In addition it is pointed out that superpositions of such states, and statistical mixtures of them, for different total photon numbers also give rise to CPT. The stability of the CPT states against decay of the cavity field modes is examined. CPT is preserved if the modes decay at the same rate. A possible method for generating statistical mixtures of the SU(2) coherent states is described.
A three-level lambda ($\ensuremath{\Lambda}$) system driven by two coherent fields at the Raman resonance condition evolves to a nonabsorbing eigenstate of the Hamiltonian called the coherent population trapping (CPT) state. We study the various factors dictating the dynamical evolution of the coherences and the populations to the CPT state. We demonstrate the formation of the CPT state even at low intensities, though it takes much longer to form such a state. For the case of unequal decay rates we demonstrate an interesting sharp dip in the steady-state response of the medium at the Raman resonance condition.