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:0906.4830

Production of Entangled X-Ray Photon Pairs by High Energy Electrons

K.A. Ispirian, M. K. Ispiryan

Published Jun 26, 2009• 1 citation
arXivHTMLPDF

Abstract

Without developing a correct theory, the rate of the production of entangled photon pairs in the X-ray region by high energy electrons is estimated for experimental parameters used in a few experiments on X-ray parametric down conversion. Taking into account the need for X-ray entangled X-ray photons, it is proposed to begin the experimental study of such mechanism of nonlinear X-ray optics before the launch of the X-ray free electron lasers.

DOI
10.48550/arxiv.0906.4830

Related papers

Entangled X-ray Photon Pair Generation by Free Electron Lasers

Haitan Xu, Linfeng Zhang, Zunqi Li +4 more

Abstract Einstein, Podolsky and Rosen's prediction on incompleteness of quantum mechanics was overturned by experimental tests on Bell's inequality that confirmed the existence of quantum entanglement. In X-ray optics, entangled photon pairs can be generated by X-ray parametric down conversion (XPDC), which is limited by relatively low efficiency. Meanwhile, free electron laser (FEL) has successfully lased at X-ray frequencies recently. However, FEL is usually seen as a classical light source, and its quantum effects are considered minor corrections to the classical theory. Here we investigate entangled X-ray photon pair emissions in FEL. We establish a theory for coherently amplified entangled photon pair emission from microbunched electron pulses in the undulator. We also propose an experimental scheme for the observation of the entangled photon pairs via energy and spatial correlation measurements. Such an entangled X-ray photon pair source is of great importance in quantum optics and other X-ray applications.

•Sep 12, 2022•0 citations

X-ray parametric down-conversion at an XFEL

N. J. Hartley, James Baxter, Scott Curtis +11 more

Understanding and harnessing X-ray quantum effects could open new, to our knowledge, frontiers in imaging and quantum optics. In this study, we measured the process of X-ray parametric down-conversion, where a single high-energy X-ray photon splits into two lower-energy photons. Using the SACLA X-ray free electron laser in Japan at 9.83 keV, we found clear evidence that pairs of photons were produced along the energy-angle relationship that conserved both energy and momentum, as predicted for down-conversion, and consistent with quantum entanglement of X-ray photons. By matching specific photon pairs for energy and momentum conservation, we observe a signal rate of 1250 pairs per hour, confirming that correlated photon pairs can be generated and observed in the absence of explicit time correlations. Our results show that with further refinement, the number of entangled photons produced per laser pulse could increase by an order of magnitude. This paves the way for demonstrating quantum-enhanced X-ray imaging, and confirmation of X-ray photon entanglement.

Optica•May 19, 2025•4 citations

Entangled X-Ray Photon Pair Generation by Free-Electron Lasers

Linfeng Zhang, Zunqi Li, Dongyu Liu +3 more

We investigate entangled x-ray photon pair emissions in a free-electron laser (FEL) and establish a quantum electrodynamical theory for coherently amplified entangled photon pair emission from microbunched electron pulses in the undulator. We provide a scheme to generate highly entangled x-ray photon pairs and numerically demonstrate the properties of entangled emission, which is of great importance in x-ray quantum optics. Our work shows a unique advantage of FELs in entangled x-ray photon pair generation.

arXiv:2208.01335•Physical Review Letters•Aug 14, 2023•14 citations

Production of entangled x rays through nonlinear double Compton scattering

T. D. C. de Vos, J. J. Postema, B. H. Schaap +2 more

An accessible tabletop source for the production of entangled x rays is crucial for the field of high-energy quantum optics. Here, we present a detailed analysis of the entanglement and polarization of the two photons emitted by an electron in an intense laser wave (nonlinear double-Compton scattering), by working within the framework of strong-field QED. By identifying contributions to the emission probability stemming from the electron being either on-shell or off-shell between the two-photon emissions, we show that the entangled photons are generated via the off-shell contribution for moderate beam energies, which are realizable on a tabletop setup. We propose an experiment to produce and isolate pairs of entangled x rays, through spectral filtering.

arXiv:2311.17807•Physical Review A•Oct 1, 2024•7 citations

Advancing X-ray quantum imaging through Monte-Carlo simulations

Pakhshan Espoukeh, Gabriel Biener, James M. Baxter +2 more

Imaging with X-rays poses fundamental limits due to radiation damage of the highly energetic photons. This becomes problematic for sensitive biological systems such as subcellular structures. Lowering the radiation dose, without sacrificing the signal-to-noise ratio, would be desirable for any kind of imaging modalities involving X-rays. To achieve this goal, quantum imaging with entangled X-ray photons constitutes a promising route. Production of biphotons have been demonstrated in the X-ray regime by the process of Spontaneous Parametric Down-Conversion (SPDC). However, compared to SPDC in the regime of visible light, the production rate for X-ray biphotons is extremely low. With the introduction of new high average brightness X-ray sources, such as 4th generation synchrotrons and high repetition rate Free-Electron X-ray Lasers (XFEL), quantum imaging may become practical. We introduce a ray tracing approach using Monte-Carlo sampling, specifically designed for quantum imaging with entangled X-ray photons generated by SPDC. By simulation, the superior image quality of quantum over classical imaging methods is demonstrated using realistic experimental conditions available at high repetition rate XFELs. With these simulations, we can efficiently assist the design of future experiments at beam lines, which can substantially accelerate the advancement of X-ray quantum imaging and reduce costs.

Scientific Reports•Jul 14, 2025•2 citations

Generation of correlated photon pairs in type-II parametric down conversion--revisited

Christian Kurtsiefer, Markus Oberparleiter, Harald Weinfurter

Type-II parametric down conversion in nonlinear optical crystals has turned out to be one of the most powerful methods to generate entangled photon pairs, and even allowed a large set of experiments on foundations of quantum mechanics and recent applications in quantum communication. In this paper, we present an experimental investigation of the emission characteristics for down-converted photons in order to investigate the possibility of high brightness sources for correlated photon pairs. Furthermore, we discuss possible ways to increase the collection efficiency for polarization entangled photon pairs.

Journal of Modern Optics•Nov 1, 2001•63 citations
Without developing a correct theory, the rate of the production of entangled photon pairs in the X-ray region by high energy electrons is estimated for experimental parameters used in a few experiments on X-ray parametric down conversion. Taking into account the need for X-ray entangled X-ray photons, it is proposed to begin the experimental study of such mechanism of nonlinear X-ray optics before the launch of the X-ray free electron lasers.
Abstract Einstein, Podolsky and Rosen's prediction on incompleteness of quantum mechanics was overturned by experimental tests on Bell's inequality that confirmed the existence of quantum entanglement. In X-ray optics, entangled photon pairs can be generated by X-ray parametric down conversion (XPDC), which is limited by relatively low efficiency. Meanwhile, free electron laser (FEL) has successfully lased at X-ray frequencies recently. However, FEL is usually seen as a classical light source, and its quantum effects are considered minor corrections to the classical theory. Here we investigate entangled X-ray photon pair emissions in FEL. We establish a theory for coherently amplified entangled photon pair emission from microbunched electron pulses in the undulator. We also propose an experimental scheme for the observation of the entangled photon pairs via energy and spatial correlation measurements. Such an entangled X-ray photon pair source is of great importance in quantum optics and other X-ray applications.
Understanding and harnessing X-ray quantum effects could open new, to our knowledge, frontiers in imaging and quantum optics. In this study, we measured the process of X-ray parametric down-conversion, where a single high-energy X-ray photon splits into two lower-energy photons. Using the SACLA X-ray free electron laser in Japan at 9.83 keV, we found clear evidence that pairs of photons were produced along the energy-angle relationship that conserved both energy and momentum, as predicted for down-conversion, and consistent with quantum entanglement of X-ray photons. By matching specific photon pairs for energy and momentum conservation, we observe a signal rate of 1250 pairs per hour, confirming that correlated photon pairs can be generated and observed in the absence of explicit time correlations. Our results show that with further refinement, the number of entangled photons produced per laser pulse could increase by an order of magnitude. This paves the way for demonstrating quantum-enhanced X-ray imaging, and confirmation of X-ray photon entanglement.
We investigate entangled x-ray photon pair emissions in a free-electron laser (FEL) and establish a quantum electrodynamical theory for coherently amplified entangled photon pair emission from microbunched electron pulses in the undulator. We provide a scheme to generate highly entangled x-ray photon pairs and numerically demonstrate the properties of entangled emission, which is of great importance in x-ray quantum optics. Our work shows a unique advantage of FELs in entangled x-ray photon pair generation.
An accessible tabletop source for the production of entangled x rays is crucial for the field of high-energy quantum optics. Here, we present a detailed analysis of the entanglement and polarization of the two photons emitted by an electron in an intense laser wave (nonlinear double-Compton scattering), by working within the framework of strong-field QED. By identifying contributions to the emission probability stemming from the electron being either on-shell or off-shell between the two-photon emissions, we show that the entangled photons are generated via the off-shell contribution for moderate beam energies, which are realizable on a tabletop setup. We propose an experiment to produce and isolate pairs of entangled x rays, through spectral filtering.
Imaging with X-rays poses fundamental limits due to radiation damage of the highly energetic photons. This becomes problematic for sensitive biological systems such as subcellular structures. Lowering the radiation dose, without sacrificing the signal-to-noise ratio, would be desirable for any kind of imaging modalities involving X-rays. To achieve this goal, quantum imaging with entangled X-ray photons constitutes a promising route. Production of biphotons have been demonstrated in the X-ray regime by the process of Spontaneous Parametric Down-Conversion (SPDC). However, compared to SPDC in the regime of visible light, the production rate for X-ray biphotons is extremely low. With the introduction of new high average brightness X-ray sources, such as 4th generation synchrotrons and high repetition rate Free-Electron X-ray Lasers (XFEL), quantum imaging may become practical. We introduce a ray tracing approach using Monte-Carlo sampling, specifically designed for quantum imaging with entangled X-ray photons generated by SPDC. By simulation, the superior image quality of quantum over classical imaging methods is demonstrated using realistic experimental conditions available at high repetition rate XFELs. With these simulations, we can efficiently assist the design of future experiments at beam lines, which can substantially accelerate the advancement of X-ray quantum imaging and reduce costs.
Type-II parametric down conversion in nonlinear optical crystals has turned out to be one of the most powerful methods to generate entangled photon pairs, and even allowed a large set of experiments on foundations of quantum mechanics and recent applications in quantum communication. In this paper, we present an experimental investigation of the emission characteristics for down-converted photons in order to investigate the possibility of high brightness sources for correlated photon pairs. Furthermore, we discuss possible ways to increase the collection efficiency for polarization entangled photon pairs.