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

arXiv:2007.15451 · Frontiers in Physics

Time and Space Resolved First Order Optical Interference Between Distinguishable Photon Paths

M. Fernández‐Guasti, C. García-Guerrero

Published Jan 24, 2022• 5 citations
arXivHTMLPDF

Abstract

Interference between different photons occurs and has been observed under diverse experimental conditions. A necessary condition in order to obtain interference fringes is the existence of at least two possible paths and unknown which-path information. If the photon beams have different frequencies, stability of the sources and fast spatially distributed detectors are required in order to detect the time displaced interference fringes. First order optical interference between two truly independent CW laser sources is observed. In contrast with the standard quantum criterion, interference is observed although the photon beams are distinguishable and, from quantum measurements, the path is unequivocally known for each photon beam. Segments of the continuous wave wavetrains are selected with an acousto-optic modulator. Temporal and spatial interference are integrated in a single combined phenomenon via streak camera detection. The displacement of the fringes in the time versus space interferograms evince the trajectories of the labeled photons. These results suggest that in non-degenerate frequency schemes, the ontology has to be refined and the which-path criterion must be precisely formulated. On the one hand, if the query refers to the frequency labeled photons, the path of each red or blue photon is known, whereas on the other hand, if the query is performed in terms of the detected photons, the path is unknown.

DOI
10.3389/fphy.2021.813565

Related papers

First Order Optical Interference between Distinguishable Photon Paths

M. Fernández‐Guasti, C. García-Guerrero

A necessary condition in order to obtain interference fringes in QED is the existence of at least two possible paths and unknown which-path information. If the photon beams have different frequencies, stability of the sources and fast enough detectors are also required. In this experiment, first order interference between two truly independent CW Nd:YAG monomode laser sources was produced. Contrary to what is expected, interference is observed although the photon beams are distinguishable and the path is unequivocally known for each photon beam. Segments of the ultra-stabilized CW wavetrains are selected with an acousto optic modulator. Temporal and spatial interference are integrated in a single combined phenomenon via streak camera detection. In this way, interference fringes and frequency beating are both present in the streak camera images. The photon beams are labeled with two slightly different frequencies. In addition, the inclination of the beams establish the projection of their respective wave vectors in the detection plane, which may be seen as perturbations coming from two different slits. The fringes displacement in the time-space interferograms reveal the trajectories of the frequency labeled photons. Since the detection probability of any one photon is independent from the detection of the rest, the trajectory can be drawn for each frequency labeled event. These results indicate that in non-degenerate frequency schemes, the ontology has to be refined and the which path criterion must be precisely stated. If reference is made to the frequency labeled photons, the path of each photon is known, whereas if the query is stated in terms of the detected photons, the path is unknown.

Photonics & Electromagnetics Research Symposium - Spring (PIERS-Spring)•Jun 1, 2019•2 citations

Observation of the First-Order Interference Fringes Beyond Coherence Length Employing Commercial Continuous-wave Multi-mode Laser Diode: A Sight of Two-photon Interference

Hongmin Liu

We report an experiment of observation of classical double-slit interference fringes of two-photon interference. In the experiment, a commercial continuous-wave multi-mode F-P laser diode without either mode-locked or frequency-locked is used as the light source, the density of photons is far more than the single-photon level, and the path difference of the long and short paths is far more than the longitudinal coherence length of the laser diode. The temporal stable and clearly visible spatial-distributed pattern, i.e. first-order interference fringes, was observed .Contradict to the prediction of single-photon interference mechanism, the interference happened far beyond the coherence length, the occurrence possibility and time duration of the interference fringes decrease with the reduction of mode number of the LD, and the time difference between the fringes disappearance and the light vanish is equal to the time difference of the two paths. After discussion, we came to the conclusion that the observed phenomena can be understood in time-resolved two-photon interference mechanism. We reveal a new method to perform two-photon first-order interference, and this help to understand the nature of two-photon interference and also can be useful for quantum information science.

arXiv:2402.15041•Feb 23, 2024•0 citations

Interference between resolvable wavelengths

Lloyd M. Davis

When a frequency stabilized dye laser (linewidth ~1 MHz) is passed through a 15.25-MHz Bragg cell, a Doppler-shifted beam emerges at a small angle. Lenses are used to cross this beam with the unshifted beam to form moving interference fringes at the photocathode of a streak camera. By using a large gain of the streak camera intensifier and an intensified low-background readout of the phosphor, single photons are detectable at the photocathode. This forms a novel Young’s experiment conducted with two resolvable frequency beams passing through one known pinhole each. If the photocathode could discriminate the frequency of the detected photon, and hence which beam it came from, or if either beam were blocked, zero visibility results. The experiment gives a direct measurement of the first-order cross-coherence at single-photon detection levels of two-frequency resolvable beams. By contrast, in quantum beat experiments only the photon probability intensity vs time is measured, and the beats are then attributed to a first-order cross-coherence of the quantum pathways. The question of the frequency spectrum and cross-spectral density of each detected photon is addressed with reference to a time-dependent physical spectrum of light.1

Annual Meeting Optical Society of America•Jan 1, 1987•0 citations

Interference between resolvable wavelengths with single-photon–resolved detection

Lloyd M. Davis

Streak-camera detection of moving interference fringes with single-photon resolution constitutes a novel Young's experiment in which the exact frequency of each detected photon cannot be specified without destroying the visibility of the interference pattern. The experiment demonstrates first-order cross spectral coherence between resolvable frequencies, in which case the optical frequency of the detected light must be calculated in terms of a time-dependent spectrum.

Physical Review Letters•Mar 28, 1988•9 citations

Quantum Optics and Informatics

Davıd L. Andrews, David S. Bradshaw

3.1 Interference of a Single Photon The kinds of study originally conducted by Thomas Young - in particular, the celebrated "double slit" experiment that we briefly examined in Chapter 1 (see Fig. 1) - provide a capacity to reveal far more than the wave nature of light, important as that is. True enough, the observed characteristic fringe pattern, when monochromatic light passes through two closely spaced slits onto a screen, appears to be simply explicable on the basis of waves from each slit undergoing constructive and destructive interference at different positions on the screen. Yet, astonishingly, these patterns of interference are still exhibited when individual photons of a low-intensity input beam reach the screen one at a time, showing that it cannot in fact be a matter of different photons having to interfere with each other. Indeed, Dirac enunciated the general principle that photons can never directly interact with each other. The double slit and other such experiments indicate that each photon interacts in a delocalized, wave-like manner with both slits at the same time. Successive experiments build interference patterns that conform to an exact mathematical distribution formula, but the position at which an individual photon is detected in any particular instance cannot be predicted; this is a quintessential illustration of quantum uncertainty. Using the path integral approach of quantum theory, the phenomenon is more accurately represented by introducing a summation over all possible routes between the source and the screen on which the pattern appears, signifying an entire "lifetime" for each photon involved in the experiment. This relates to the fact that the actual trajectory is unknown without an observation, and thus we only obtain the probabilities of the photon striking the screen at different positions and times; all trajectories (potentialities) must be considered in a superposition. Each route is considered equally probable, and the variation in phase produces quantum interference. The differences in phase of each trajectory, at varying positions on the screen, generates the fringe pattern. An intriguing variation on this experiment involves "marking" the photons so that the actual route of each photon to the screen is known. Remarkably, in such a case, the fringe patterns do not appear because quantum interference cannot occur. A consequence of the observation of the photon route is an effect that, in other quantum mechanical connections, is known as a collapse of the wavefunction. However, it is possible for the fringe patterns to reappear when information on the route of the photons is lost; this is known as a quantum eraser.

SPIE eBooks•Aug 1, 2018•0 citations

Second-order interference of two independent and tunable single-mode continuous-wave lasers

Jianbin Liu, Dong Wei, Hui Chen +5 more

The second-order temporal interference of two independent single-mode continuous-wave lasers is discussed by employing two-photon interference in Feynman's path integral theory. It is concluded that whether the second-order temporal interference pattern can or cannot be retrieved via two-photon coincidence counting rate is dependent on the resolution time of the detection system and the frequency difference between these two lasers. Two identical and tunable single-mode continuous-wave diode lasers are employed to verify the predictions. These studies are helpful to understand the physics of two-photon interference with photons of different spectra.

arXiv:1501.05707•Chinese Physics B•Mar 1, 2016•11 citations
Interference between different photons occurs and has been observed under diverse experimental conditions. A necessary condition in order to obtain interference fringes is the existence of at least two possible paths and unknown which-path information. If the photon beams have different frequencies, stability of the sources and fast spatially distributed detectors are required in order to detect the time displaced interference fringes. First order optical interference between two truly independent CW laser sources is observed. In contrast with the standard quantum criterion, interference is observed although the photon beams are distinguishable and, from quantum measurements, the path is unequivocally known for each photon beam. Segments of the continuous wave wavetrains are selected with an acousto-optic modulator. Temporal and spatial interference are integrated in a single combined phenomenon via streak camera detection. The displacement of the fringes in the time versus space interferograms evince the trajectories of the labeled photons. These results suggest that in non-degenerate frequency schemes, the ontology has to be refined and the which-path criterion must be precisely formulated. On the one hand, if the query refers to the frequency labeled photons, the path of each red or blue photon is known, whereas on the other hand, if the query is performed in terms of the detected photons, the path is unknown.
A necessary condition in order to obtain interference fringes in QED is the existence of at least two possible paths and unknown which-path information. If the photon beams have different frequencies, stability of the sources and fast enough detectors are also required. In this experiment, first order interference between two truly independent CW Nd:YAG monomode laser sources was produced. Contrary to what is expected, interference is observed although the photon beams are distinguishable and the path is unequivocally known for each photon beam. Segments of the ultra-stabilized CW wavetrains are selected with an acousto optic modulator. Temporal and spatial interference are integrated in a single combined phenomenon via streak camera detection. In this way, interference fringes and frequency beating are both present in the streak camera images. The photon beams are labeled with two slightly different frequencies. In addition, the inclination of the beams establish the projection of their respective wave vectors in the detection plane, which may be seen as perturbations coming from two different slits. The fringes displacement in the time-space interferograms reveal the trajectories of the frequency labeled photons. Since the detection probability of any one photon is independent from the detection of the rest, the trajectory can be drawn for each frequency labeled event. These results indicate that in non-degenerate frequency schemes, the ontology has to be refined and the which path criterion must be precisely stated. If reference is made to the frequency labeled photons, the path of each photon is known, whereas if the query is stated in terms of the detected photons, the path is unknown.
We report an experiment of observation of classical double-slit interference fringes of two-photon interference. In the experiment, a commercial continuous-wave multi-mode F-P laser diode without either mode-locked or frequency-locked is used as the light source, the density of photons is far more than the single-photon level, and the path difference of the long and short paths is far more than the longitudinal coherence length of the laser diode. The temporal stable and clearly visible spatial-distributed pattern, i.e. first-order interference fringes, was observed .Contradict to the prediction of single-photon interference mechanism, the interference happened far beyond the coherence length, the occurrence possibility and time duration of the interference fringes decrease with the reduction of mode number of the LD, and the time difference between the fringes disappearance and the light vanish is equal to the time difference of the two paths. After discussion, we came to the conclusion that the observed phenomena can be understood in time-resolved two-photon interference mechanism. We reveal a new method to perform two-photon first-order interference, and this help to understand the nature of two-photon interference and also can be useful for quantum information science.
When a frequency stabilized dye laser (linewidth ~1 MHz) is passed through a 15.25-MHz Bragg cell, a Doppler-shifted beam emerges at a small angle. Lenses are used to cross this beam with the unshifted beam to form moving interference fringes at the photocathode of a streak camera. By using a large gain of the streak camera intensifier and an intensified low-background readout of the phosphor, single photons are detectable at the photocathode. This forms a novel Young’s experiment conducted with two resolvable frequency beams passing through one known pinhole each. If the photocathode could discriminate the frequency of the detected photon, and hence which beam it came from, or if either beam were blocked, zero visibility results. The experiment gives a direct measurement of the first-order cross-coherence at single-photon detection levels of two-frequency resolvable beams. By contrast, in quantum beat experiments only the photon probability intensity vs time is measured, and the beats are then attributed to a first-order cross-coherence of the quantum pathways. The question of the frequency spectrum and cross-spectral density of each detected photon is addressed with reference to a time-dependent physical spectrum of light.1
3.1 Interference of a Single Photon The kinds of study originally conducted by Thomas Young - in particular, the celebrated "double slit" experiment that we briefly examined in Chapter 1 (see Fig. 1) - provide a capacity to reveal far more than the wave nature of light, important as that is. True enough, the observed characteristic fringe pattern, when monochromatic light passes through two closely spaced slits onto a screen, appears to be simply explicable on the basis of waves from each slit undergoing constructive and destructive interference at different positions on the screen. Yet, astonishingly, these patterns of interference are still exhibited when individual photons of a low-intensity input beam reach the screen one at a time, showing that it cannot in fact be a matter of different photons having to interfere with each other. Indeed, Dirac enunciated the general principle that photons can never directly interact with each other. The double slit and other such experiments indicate that each photon interacts in a delocalized, wave-like manner with both slits at the same time. Successive experiments build interference patterns that conform to an exact mathematical distribution formula, but the position at which an individual photon is detected in any particular instance cannot be predicted; this is a quintessential illustration of quantum uncertainty. Using the path integral approach of quantum theory, the phenomenon is more accurately represented by introducing a summation over all possible routes between the source and the screen on which the pattern appears, signifying an entire "lifetime" for each photon involved in the experiment. This relates to the fact that the actual trajectory is unknown without an observation, and thus we only obtain the probabilities of the photon striking the screen at different positions and times; all trajectories (potentialities) must be considered in a superposition. Each route is considered equally probable, and the variation in phase produces quantum interference. The differences in phase of each trajectory, at varying positions on the screen, generates the fringe pattern. An intriguing variation on this experiment involves "marking" the photons so that the actual route of each photon to the screen is known. Remarkably, in such a case, the fringe patterns do not appear because quantum interference cannot occur. A consequence of the observation of the photon route is an effect that, in other quantum mechanical connections, is known as a collapse of the wavefunction. However, it is possible for the fringe patterns to reappear when information on the route of the photons is lost; this is known as a quantum eraser.
The second-order temporal interference of two independent single-mode continuous-wave lasers is discussed by employing two-photon interference in Feynman's path integral theory. It is concluded that whether the second-order temporal interference pattern can or cannot be retrieved via two-photon coincidence counting rate is dependent on the resolution time of the detection system and the frequency difference between these two lasers. Two identical and tunable single-mode continuous-wave diode lasers are employed to verify the predictions. These studies are helpful to understand the physics of two-photon interference with photons of different spectra.