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

Chinese Physics Letters

Coherent Population Trapping Induced by Phase Modulated and Fluctuating Fields

Jian Wang, Xiangming Hu

Published Jan 18, 2007• 2 citations
Publisher

Abstract

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.

DOI
10.1088/0256-307x/24/2/034

Related papers

Coherent Population Trapping

Bryan J. Dalton, R. G. Mcduff, P. L. Knight

Coherent trapping in three level lambda and ladder systems is examined for the case of two fluctuating laser fields with unequal bandwidths, obtained by frequency multiplying methods. The inclusion of uncorrelated laser fields destroys trapping and washes out the narrow coherence hole in the fluorescent intensity. However, if the fields are positively critically cross-correlated, the relevant atomic coherences in lambda systems are much less affected by the laser fluctuations. A significant degree of trapping re-occurs and the narrow coherence hole is largely restored. An enhancement of the destruction of coherent trapping occurs in ladder systems. An application of the theory to molecular photodissociation is discussed.

Optica Acta International Journal of Optics•Jan 1, 1985•73 citations

The effects of laser field fluctuations on coherent population trapping

Bryan J. Dalton, P. L. Knight

A three-level system driven by two coherent fields on two-photon resonance leads to the trapping of population in a superposition of initial and final states which is immune to further photoexcitation, manifesting itself in a narrow coherence minimum in the absorption spectrum. The authors analyse the effects of laser field bandwidths and cross-correlations on these phenomena. They find that the inclusion of laser bandwidths dephases atomic coherences which leads to the destruction of population trapping and of the narrow coherence minimum in the absorption spectrum. When the driving fields are not cross-correlated, the atomic coherences are similarly dephased in both lambda and ladder systems. If, however, the driving fields are critically cross-correlated, two-photon coherences in the lambda system are unaffected by laser fluctuations; trapping and the coherence minimum persist. For the ladder system, on the other hand, the cross-correlation does not restore the atomic coherences involved.

Journal of Physics B Atomic and Molecular Physics•Nov 14, 1982•152 citations

Non-stationary coherent population trapping in frequency-modulated fields

Vladimir Leonardovich Derbov, Alexey S. Lyubimov

Coherent population trapping (CPT) resonance formation is modeled numerically in a three-level Λ -system with one of the near-resonance fields being frequency-modulated. The model is based on density matrix equations in RW approximation with atomic relaxation properly taken into account. Slow modulation is shown to be equivalent to CW excitation with the frequency changed point by point. As the modulation period approaches the relaxation times, the delayed response of the system is shown to cause the CPT resonance shift and reshaping, as well as the appearance of transient oscillations of the energy level populations.

CAOL . International Conference on Advanced Optoelectronics and Lasers•Sep 1, 2010•0 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

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

Controlling quantum fluctuations by electromagnetic field induced coherences

G. S. Agarwal

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.>

Nonlinear Optics•Dec 17, 2002•0 citations
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.
Coherent trapping in three level lambda and ladder systems is examined for the case of two fluctuating laser fields with unequal bandwidths, obtained by frequency multiplying methods. The inclusion of uncorrelated laser fields destroys trapping and washes out the narrow coherence hole in the fluorescent intensity. However, if the fields are positively critically cross-correlated, the relevant atomic coherences in lambda systems are much less affected by the laser fluctuations. A significant degree of trapping re-occurs and the narrow coherence hole is largely restored. An enhancement of the destruction of coherent trapping occurs in ladder systems. An application of the theory to molecular photodissociation is discussed.
A three-level system driven by two coherent fields on two-photon resonance leads to the trapping of population in a superposition of initial and final states which is immune to further photoexcitation, manifesting itself in a narrow coherence minimum in the absorption spectrum. The authors analyse the effects of laser field bandwidths and cross-correlations on these phenomena. They find that the inclusion of laser bandwidths dephases atomic coherences which leads to the destruction of population trapping and of the narrow coherence minimum in the absorption spectrum. When the driving fields are not cross-correlated, the atomic coherences are similarly dephased in both lambda and ladder systems. If, however, the driving fields are critically cross-correlated, two-photon coherences in the lambda system are unaffected by laser fluctuations; trapping and the coherence minimum persist. For the ladder system, on the other hand, the cross-correlation does not restore the atomic coherences involved.
Coherent population trapping (CPT) resonance formation is modeled numerically in a three-level Λ -system with one of the near-resonance fields being frequency-modulated. The model is based on density matrix equations in RW approximation with atomic relaxation properly taken into account. Slow modulation is shown to be equivalent to CW excitation with the frequency changed point by point. As the modulation period approaches the relaxation times, the delayed response of the system is shown to cause the CPT resonance shift and reshaping, as well as the appearance of transient oscillations of the energy level populations.
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.
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.