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

Forced indistinguishability in induced coherence without induced emission

G. A. Barbosa

Published May 8, 1994• 0 citations
OpenAlex

Abstract

Induced coherence without induced emission has been obtained, in Mandel's group, through the alignment of the idler beams produced by two nonlinear crystals in parametric downconversion processes. The interference resulting between the two spontaneous signal beams emitted by the crystals is explained by the relationship between degree of coherence and degree of indistinguishability. Although the quantitative understanding of this interference has yet to be understood, the degree of visibility obtained from those interference patterns reflects the phase correlation established between the signal emission of the two crystals in the spontaneous downconversion process. Those experiments have explored this nonclassical phenomenon by inserting absorbers in the idler connection path between the two crystals, by insertion of optical delays, and even by a topological modification of the connection path by Pancharatnam's or Berry's phase in the optical domain. In all the experiments performed to date, the variations introduced in the connection path deliberately decreased the degree of indistinguishability and, consequently, the degree of coherence.

Related papers

Forced indistinguishability in ‘‘induced coherence without stimulated emission’’

G. A. Barbosa

The nonclassical phenomenon of ``induced coherence without simulated emission'' is analyzed under the condition where two nonlinear ${\mathrm{\ensuremath{\chi}}}^{(2)}$ crystals are aligned in such a way that their idler emissions are collinear and inside a ringlike cavity with loss. This forced indistinguishability of the idler photons produces an interference between the free traveling conjugated signal beams when they are superposed. This interference is independent of the cavity loss, within the limits of a single-mode theory, and highly dependent on the position of the crystals inside the cavity. The maximum obtainable visibility of 100% reflects an induced coherence in the two crystals by the cavity field.

Physical Review A•Oct 1, 1994•4 citations

Induced coherence without induced emission resulting in nonlocal interference

X. Y. Zou, L. J. Wang, L. Mandeļ

Although induced coherence is generally associated with induced or stimulated emission, in the process of spontaneous parametric downconversion of light induced coherence can be generated on its own. This is demonstrated in an experiment in which the signal beams from two coherently pumped downconverters come together and interfere whenever the idler beam from the first downconverter (DC1) passes through and is aligned with the second downconverter (DC2). Misaligning the idlers, or blocking the first idler, makes the interference disappear. More generally, the degree of coherence can be controlled by varying the amplitude of the idler from DC1 that reaches DC2. The interpretation of this nonclassical interference is discussed in terms of the interpretation of the wave function or state vector of the emitted photon.

Annual Meeting Optical Society of America•Jan 1, 1991•0 citations

Induced coherence without induced emission

L. J. Wang, X. Y. Zou, L. Mandeļ

An interference experiment with signal and idler photons produced by parametric down-conversion in two nonlinear crystals is described and analyzed theoretically. It is found that when the idlers for the two crystals are superposed and aligned, the idler photon from the first crystal can induce coherence between the two signals, but without inducing any additional emission. Blocking the first idler wipes out the interference. The implications for the interpretation of the quantum state vector are discussed, and this leads to the conclusion that the state reflects not only what is known, but to some extent also what is knowable in principle.

Physical Review A•Oct 1, 1991•342 citations

Complementarity in biphoton generation with stimulated or induced coherence

Axel Heuer, R. W. Menzel, Peter W. Milonni

Coherence can be induced or stimulated in parametric down-conversion using two or three crystals when, for example, the idler modes of the crystals are aligned. Previous experiments with induced coherence [Phys. Rev. Lett. 114, 053601 (2015)] focused on which-path information and the role of vacuum fields in realizing complementarity via reduced visibility in single-photon interference. Here we describe experiments comparing induced and stimulated coherence. Different single-photon interference experiments were performed by blocking one of the pump beams in a three-crystal setup. Each counted photon is emitted from one of two crystals and which-way information may or not be available, depending on the setup. Distinctly different results are obtained in the induced and stimulated cases, especially when a variable transmission filter is inserted between the crystals. A simplified theoretical model accounts for all the experimental results and is also used to address the question of whether the phases of the signal and idler fields in parametric down-conversion are correlated.

arXiv:1506.00457•Physical Review A•Sep 18, 2015•40 citations

Observation of a nonlocal Pancharatnam phase shift in the process of induced coherence without induced emission

Timothy P. Grayson, J. R. Torgerson, G. A. Barbosa

A Pancharatnam phase shift, which is similar to Berry's topological phase, is introduced into the idler path between two down-converters in an experiment on induced coherence without induced emission. Although the idler beams in such an experiment do not take part in interference, the Pancharatnam phase shift is observable in the interference of the signal beams. This is clearly a nonlocal manifestation of Pancharatnam's phase.

Physical Review A•Jan 1, 1994•24 citations

Induced coherence and indistinguishability in optical interference

X. Y. Zou, L. J. Wang, L. Mandeļ

Second-order interference is observed in the superposition of signal photons from two coherently pumped parametric down-converters, when the paths of the idler photons are aligned. The interference exhibits certain nonclassical features; it disappears when the idlers are misaligned or separated by a beam stop. The interpretation of this effect is discussed in terms of the intrinsic indistinguishability of the photon paths.

Physical Review Letters•Jul 15, 1991•641 citations
Induced coherence without induced emission has been obtained, in Mandel's group, through the alignment of the idler beams produced by two nonlinear crystals in parametric downconversion processes. The interference resulting between the two spontaneous signal beams emitted by the crystals is explained by the relationship between degree of coherence and degree of indistinguishability. Although the quantitative understanding of this interference has yet to be understood, the degree of visibility obtained from those interference patterns reflects the phase correlation established between the signal emission of the two crystals in the spontaneous downconversion process. Those experiments have explored this nonclassical phenomenon by inserting absorbers in the idler connection path between the two crystals, by insertion of optical delays, and even by a topological modification of the connection path by Pancharatnam's or Berry's phase in the optical domain. In all the experiments performed to date, the variations introduced in the connection path deliberately decreased the degree of indistinguishability and, consequently, the degree of coherence.
The nonclassical phenomenon of ``induced coherence without simulated emission'' is analyzed under the condition where two nonlinear ${\mathrm{\ensuremath{\chi}}}^{(2)}$ crystals are aligned in such a way that their idler emissions are collinear and inside a ringlike cavity with loss. This forced indistinguishability of the idler photons produces an interference between the free traveling conjugated signal beams when they are superposed. This interference is independent of the cavity loss, within the limits of a single-mode theory, and highly dependent on the position of the crystals inside the cavity. The maximum obtainable visibility of 100% reflects an induced coherence in the two crystals by the cavity field.
Although induced coherence is generally associated with induced or stimulated emission, in the process of spontaneous parametric downconversion of light induced coherence can be generated on its own. This is demonstrated in an experiment in which the signal beams from two coherently pumped downconverters come together and interfere whenever the idler beam from the first downconverter (DC1) passes through and is aligned with the second downconverter (DC2). Misaligning the idlers, or blocking the first idler, makes the interference disappear. More generally, the degree of coherence can be controlled by varying the amplitude of the idler from DC1 that reaches DC2. The interpretation of this nonclassical interference is discussed in terms of the interpretation of the wave function or state vector of the emitted photon.
An interference experiment with signal and idler photons produced by parametric down-conversion in two nonlinear crystals is described and analyzed theoretically. It is found that when the idlers for the two crystals are superposed and aligned, the idler photon from the first crystal can induce coherence between the two signals, but without inducing any additional emission. Blocking the first idler wipes out the interference. The implications for the interpretation of the quantum state vector are discussed, and this leads to the conclusion that the state reflects not only what is known, but to some extent also what is knowable in principle.
Coherence can be induced or stimulated in parametric down-conversion using two or three crystals when, for example, the idler modes of the crystals are aligned. Previous experiments with induced coherence [Phys. Rev. Lett. 114, 053601 (2015)] focused on which-path information and the role of vacuum fields in realizing complementarity via reduced visibility in single-photon interference. Here we describe experiments comparing induced and stimulated coherence. Different single-photon interference experiments were performed by blocking one of the pump beams in a three-crystal setup. Each counted photon is emitted from one of two crystals and which-way information may or not be available, depending on the setup. Distinctly different results are obtained in the induced and stimulated cases, especially when a variable transmission filter is inserted between the crystals. A simplified theoretical model accounts for all the experimental results and is also used to address the question of whether the phases of the signal and idler fields in parametric down-conversion are correlated.