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:2604.02541

A perfect crystal neutron loop cavity

Owen Lailey, Dusan Sarenac, David G. Cory, M. G. Huber, Dmitry A. Pushin

Published Apr 2, 2026• 0 citations
arXivHTMLPDF

Abstract

Coherent control of neutrons via Bragg diffraction forms the foundation of perfect crystal neutron interferometry, facilitating both fundamental tests of quantum mechanics and applications in quantum information science. In cavity geometries, perfect crystals enable neutron confinement and have been employed in precision measurements of spin-orbit interactions and for neutron electric dipole moment (nEDM) searches. However, in these conventional configurations, neutrons undergo a single pass through the crystal geometry, placing a physical constraint on both crystal and in-flight interaction times and measurement sensitivity. In this work, we introduce a neutron loop cavity that coherently recirculates neutrons through repeated Bragg reflections between perfect silicon crystal blades. This structure is predicted to achieve a neutron survival probability of $\sim64~\%$ for 10,000 Bragg reflections, corresponding to confinement times on the order of seconds. We propose a Schwinger interaction measurement that achieves a $π$ spin rotation in 800 Bragg reflections, representing more than a tenfold improvement in sensitivity over recent measurements. Further applications include high-sensitivity nEDM searches targeting the $10^{-27}~$e$\cdot$cm scale, as well as competitive experimental tests of neutron parity violation, the neutron lifetime, and the quantum Zeno effect with neutrons.

DOI
10.48550/arxiv.2604.02541

Related papers

Neutron Quantum States under Confined and Zeno-Like Conditions

H. Rauch

A double-loop perfect crystal neutron interferometer has been used for novel quantum state reconstruction experiments. For the measurement of combined spatial and momentum distributions a quadrature method has been used which permits the reconstruction of the related Wigner function. When neutrons pass through narrow slits the transverse momentum quantization causes a confinement-induced phase shift which has been measured by neutron inter-ferometry. The related wave fields for reflecting and absorbing walls have been calculated and mapped in form of wave carpets. It is of interest to note that just those neutrons contribute to the phase shift which classically do not touch the walls. In another set-up installed at the pulsed neutron spallation source ISIS neutrons can be trapped between perfect crystal plates for several seconds. This enables a multiple passage of the same neutron through a spin rotation unit, which provides the basis for new Zeno-effect experiments. Unavoidable quantum losses will be discussed and it will be shown how they become relevant for the quantum measuring process.

Journal of the Physical Society of Japan•Jan 1, 2003•1 citation

Neutron interferometric tests of quantum mechanics

H. Rauch

Since the invention of perfect crystal neutron interferometry this technique has become an important tool in the realization of many textbook experiments in quantum mechanics. Widely separated coherent beams of thermal neutrons are produced and superposed by dynamical Bragg diffraction from a properly shaped perfect crystal. The observed interference patterns show the characteristic coherence properties of matter waves which arc influenced by the individual particle and by the properties of the experimental device. The verification of the 4π-periodicity of spinor wavefunctions and the realization of thc spin-superposition experiment on B macroscopic scale has become feasible by this technique. A new kind of a quantum beat effect with an energy sensitivity of 2.7 × 20−-19 eV has been observed in a double coil resonance experiment. The influence of gravity and of the Earth's rotation on the wavefunction become visible at a level of an elementary particle with non-zero mass. All the results are in agreement with the formulation of quantum mechanics but, nevertheless, they stimulate discussion about its interpretation. The particle-wave dualism becomes obvious on a macroscopic scale and with a beam of massive particles.

Contemporary Physics•Jul 1, 1986•28 citations

Neutron interferometry: a tale of three continents

Tony Klein

his was one of the conclusions that emerged from the Vienna Symposium on the Foundations of Modern Physics held in June this year.Organised by Anton Zeilinger, ably assisted by Markus Aspelmeyer and the staff of the Institute of Quantum Optics and Quantum Information (IQOQI) this Symposium, the 2 nd in the series, also served as a Fest-schri for Helmut Rauch and Danny Greenberger, noted experimental and theoretical luminaries in the field.In particular,it was Helmut Rauch who,together withWolfgang Treimer and Ulrich Bonse, was first to demonstrate the first Single Crystal Neutron Interferometer in 1974 [1].Closely analogous to a Mach-Zehnder Interferometer in classical optics, these wonderful devices are carved out of a monolithic piece of highly perfect single crystal of silicon,of the kind used in the semiconductor electronics industry.A photograph and a schematic are shown in fig 1. ree parallel slabs of silicon,connected by a base,contain perfectly aligned planes of atoms,which,by virtue of Bragg Diffraction, coherently split a beam of monochromatic neutrons, whose wavelengths are comparable in magnitude to the lattice spacing of the silicon crystal.Furthermore, the silicon is almost completely transparent to neutrons -so that absorption is essentially negligible.us, the first slab acts as a beam splitter, with a transmitted and a diffracted beam emerging from it.Both these beams continue to the second slab at which Bragg diffraction occurs once again.Ignoring the transmitted beams (which escape from the system), the two diffracted beams continue on their way to the third, equidistant slab, where they recombine in a way similar to the first beam splitter.

Europhysics news•Nov 1, 2009•5 citations

Pendellösung length-scale neutron and X-ray interferometry

Owen Lailey, Alexandre Boutot, David G. Cory +12 more

Neutron and X-ray perfect-crystal interferometers (PCIs) are powerful platforms for studies of fundamental physics and phase-contrast imaging. Further enhancing several PCI capabilities requires reducing crystal blade thickness to the micron scale, which minimizes dynamical-diffraction image blur, permits operation in the pendellösung regime where blade thickness controls beam splitting, and reduces absorption for simultaneous neutron and X-ray operation. However, fabricating multiple crystal blades with identical micrometer-scale thicknesses over centimeter-scale areas remains a major challenge. Here, using a non-etching sub-micron fabrication technique, we demonstrate silicon triple-Laue interferometers with equal-blade-thicknesses of 110 $μ$m and 350 $μ$m, operated with both neutrons and X-rays. These devices are the thinnest PCIs realized to date, enabling a factor-of-six reduction in dynamical-diffraction beam spreading for improved phase-contrast imaging, while reaching the single pendellösung length regime in which crystal thickness provides an experimentally accessible control parameter for engineered quantum-optical beam splitting of plane-wave inputs. These results motivate multi-blade PCI designs utilizing identical half-pendellösung crystal lamellae that are proposed for neutron spin--orbit and electric dipole moment measurements.

physics.app-phCross-listedarXiv:2609.24709•Sep 22, 2026

Neutron Interferometry

Helmut Rauch, Samuel A. Werner

Abstract The quantum interference of DeBroglie matter waves is probably one of the most startling and fundamental aspect of quantum mechanics. It continues to tax our imaginations and leads us to new experimental windows on nature. Quantum interference phenomena are vividly displayed in the wide assembly of neutron interferometry experiments, which have been carried out since the first demonstration of a perfect silicon crystal interferometer in 1974. Since the neutron experiences all four fundamental forces of nature (strong, weak, electromagnetic, and gravitational), interferometry with neutrons provides a fertile testing ground for theory and precision measurements. Many Gedanken experiments of quantum mechanics have become real due to neutron interferometry. This book provides the reader with a detailed account of neutron interferometry experiments. The basic ideas and experiments related to coherence properties of matter waves and various post-selection criteria, gravitationally induced phase shifts, Berry's geometrical phase, spinor symmetry and spin superposition, Aharonov-Bohm topological interference effects, and the neutron version of the Sagnac effect are presented in a self-contained and pedagogical way. Interferometry with perfect crystals, artificial lattices, and spin-echo systems are topics of this book. It includes the theoretical motivations as well as connections to other areas of experimental physics, such as quantum optics, nuclear physics, gravitation, and atom interferometry. The book is written in a style that will be suitable at the beginning graduate level, and will excite many students and researchers in neutron physics, quantum optics, and atomic physics. Lecturers teaching courses in modern physics and quantum mechanics will find a number of interesting and historic experiments they may want to include in their lectures.

•Aug 10, 2000•315 citations

The neutron hidden in quantum waves

H. Rauch

The curious dual nature of the neutron (sometimes a particle, sometimes a wave) is wonderfully manifested in the various non-local interference effects observed in neutron interferometry. Here we deal with unavoidable quantum losses as they appear in neutron phase-echo and spin rotation experiments. In all cases of an interaction, parasitic beams are produced which cannot be recombined with the original beam in an ideal way. This means that a complete reconstruction of the original state would, in principle, be impossible. Thus a kind of intrinsic irreversibility occurs, even when the original quantum state survives to a very high extent. Even small interaction potentials can have huge effects when they are applied periodically and resonance effects appear. This gives various constraints for repetitive measurements and prevents a complete freezing of a quantum state in Zeno-like experiments. Additionally, a spectral change occurs, due to the dispersive action of the interaction, which has to be taken into account when many repetitive measurements are considered. A dedicated proposal for a repetitive neutron spin rotation experiment within a perfect crystal resonator will be analysed in detail. Unavoidable losses due to quantum phenomena can be separated from losses caused by experimental imperfections.

Journal of Optics B Quantum and Semiclassical Optics•Aug 1, 2002•0 citations
Coherent control of neutrons via Bragg diffraction forms the foundation of perfect crystal neutron interferometry, facilitating both fundamental tests of quantum mechanics and applications in quantum information science. In cavity geometries, perfect crystals enable neutron confinement and have been employed in precision measurements of spin-orbit interactions and for neutron electric dipole moment (nEDM) searches. However, in these conventional configurations, neutrons undergo a single pass through the crystal geometry, placing a physical constraint on both crystal and in-flight interaction times and measurement sensitivity. In this work, we introduce a neutron loop cavity that coherently recirculates neutrons through repeated Bragg reflections between perfect silicon crystal blades. This structure is predicted to achieve a neutron survival probability of ∼64 %\sim64~\%∼64 % for 10,000 Bragg reflections, corresponding to confinement times on the order of seconds. We propose a Schwinger interaction measurement that achieves a πππ spin rotation in 800 Bragg reflections, representing more than a tenfold improvement in sensitivity over recent measurements. Further applications include high-sensitivity nEDM searches targeting the 10−27 10^{-27}~10−27 e⋅\cdot⋅cm scale, as well as competitive experimental tests of neutron parity violation, the neutron lifetime, and the quantum Zeno effect with neutrons.
A double-loop perfect crystal neutron interferometer has been used for novel quantum state reconstruction experiments. For the measurement of combined spatial and momentum distributions a quadrature method has been used which permits the reconstruction of the related Wigner function. When neutrons pass through narrow slits the transverse momentum quantization causes a confinement-induced phase shift which has been measured by neutron inter-ferometry. The related wave fields for reflecting and absorbing walls have been calculated and mapped in form of wave carpets. It is of interest to note that just those neutrons contribute to the phase shift which classically do not touch the walls. In another set-up installed at the pulsed neutron spallation source ISIS neutrons can be trapped between perfect crystal plates for several seconds. This enables a multiple passage of the same neutron through a spin rotation unit, which provides the basis for new Zeno-effect experiments. Unavoidable quantum losses will be discussed and it will be shown how they become relevant for the quantum measuring process.
Since the invention of perfect crystal neutron interferometry this technique has become an important tool in the realization of many textbook experiments in quantum mechanics. Widely separated coherent beams of thermal neutrons are produced and superposed by dynamical Bragg diffraction from a properly shaped perfect crystal. The observed interference patterns show the characteristic coherence properties of matter waves which arc influenced by the individual particle and by the properties of the experimental device. The verification of the 4π-periodicity of spinor wavefunctions and the realization of thc spin-superposition experiment on B macroscopic scale has become feasible by this technique. A new kind of a quantum beat effect with an energy sensitivity of 2.7 × 20−-19 eV has been observed in a double coil resonance experiment. The influence of gravity and of the Earth's rotation on the wavefunction become visible at a level of an elementary particle with non-zero mass. All the results are in agreement with the formulation of quantum mechanics but, nevertheless, they stimulate discussion about its interpretation. The particle-wave dualism becomes obvious on a macroscopic scale and with a beam of massive particles.
his was one of the conclusions that emerged from the Vienna Symposium on the Foundations of Modern Physics held in June this year.Organised by Anton Zeilinger, ably assisted by Markus Aspelmeyer and the staff of the Institute of Quantum Optics and Quantum Information (IQOQI) this Symposium, the 2 nd in the series, also served as a Fest-schri for Helmut Rauch and Danny Greenberger, noted experimental and theoretical luminaries in the field.In particular,it was Helmut Rauch who,together withWolfgang Treimer and Ulrich Bonse, was first to demonstrate the first Single Crystal Neutron Interferometer in 1974 [1].Closely analogous to a Mach-Zehnder Interferometer in classical optics, these wonderful devices are carved out of a monolithic piece of highly perfect single crystal of silicon,of the kind used in the semiconductor electronics industry.A photograph and a schematic are shown in fig 1. ree parallel slabs of silicon,connected by a base,contain perfectly aligned planes of atoms,which,by virtue of Bragg Diffraction, coherently split a beam of monochromatic neutrons, whose wavelengths are comparable in magnitude to the lattice spacing of the silicon crystal.Furthermore, the silicon is almost completely transparent to neutrons -so that absorption is essentially negligible.us, the first slab acts as a beam splitter, with a transmitted and a diffracted beam emerging from it.Both these beams continue to the second slab at which Bragg diffraction occurs once again.Ignoring the transmitted beams (which escape from the system), the two diffracted beams continue on their way to the third, equidistant slab, where they recombine in a way similar to the first beam splitter.
Neutron and X-ray perfect-crystal interferometers (PCIs) are powerful platforms for studies of fundamental physics and phase-contrast imaging. Further enhancing several PCI capabilities requires reducing crystal blade thickness to the micron scale, which minimizes dynamical-diffraction image blur, permits operation in the pendellösung regime where blade thickness controls beam splitting, and reduces absorption for simultaneous neutron and X-ray operation. However, fabricating multiple crystal blades with identical micrometer-scale thicknesses over centimeter-scale areas remains a major challenge. Here, using a non-etching sub-micron fabrication technique, we demonstrate silicon triple-Laue interferometers with equal-blade-thicknesses of 110 μμμm and 350 μμμm, operated with both neutrons and X-rays. These devices are the thinnest PCIs realized to date, enabling a factor-of-six reduction in dynamical-diffraction beam spreading for improved phase-contrast imaging, while reaching the single pendellösung length regime in which crystal thickness provides an experimentally accessible control parameter for engineered quantum-optical beam splitting of plane-wave inputs. These results motivate multi-blade PCI designs utilizing identical half-pendellösung crystal lamellae that are proposed for neutron spin--orbit and electric dipole moment measurements.
Abstract The quantum interference of DeBroglie matter waves is probably one of the most startling and fundamental aspect of quantum mechanics. It continues to tax our imaginations and leads us to new experimental windows on nature. Quantum interference phenomena are vividly displayed in the wide assembly of neutron interferometry experiments, which have been carried out since the first demonstration of a perfect silicon crystal interferometer in 1974. Since the neutron experiences all four fundamental forces of nature (strong, weak, electromagnetic, and gravitational), interferometry with neutrons provides a fertile testing ground for theory and precision measurements. Many Gedanken experiments of quantum mechanics have become real due to neutron interferometry. This book provides the reader with a detailed account of neutron interferometry experiments. The basic ideas and experiments related to coherence properties of matter waves and various post-selection criteria, gravitationally induced phase shifts, Berry's geometrical phase, spinor symmetry and spin superposition, Aharonov-Bohm topological interference effects, and the neutron version of the Sagnac effect are presented in a self-contained and pedagogical way. Interferometry with perfect crystals, artificial lattices, and spin-echo systems are topics of this book. It includes the theoretical motivations as well as connections to other areas of experimental physics, such as quantum optics, nuclear physics, gravitation, and atom interferometry. The book is written in a style that will be suitable at the beginning graduate level, and will excite many students and researchers in neutron physics, quantum optics, and atomic physics. Lecturers teaching courses in modern physics and quantum mechanics will find a number of interesting and historic experiments they may want to include in their lectures.
The curious dual nature of the neutron (sometimes a particle, sometimes a wave) is wonderfully manifested in the various non-local interference effects observed in neutron interferometry. Here we deal with unavoidable quantum losses as they appear in neutron phase-echo and spin rotation experiments. In all cases of an interaction, parasitic beams are produced which cannot be recombined with the original beam in an ideal way. This means that a complete reconstruction of the original state would, in principle, be impossible. Thus a kind of intrinsic irreversibility occurs, even when the original quantum state survives to a very high extent. Even small interaction potentials can have huge effects when they are applied periodically and resonance effects appear. This gives various constraints for repetitive measurements and prevents a complete freezing of a quantum state in Zeno-like experiments. Additionally, a spectral change occurs, due to the dispersive action of the interaction, which has to be taken into account when many repetitive measurements are considered. A dedicated proposal for a repetitive neutron spin rotation experiment within a perfect crystal resonator will be analysed in detail. Unavoidable losses due to quantum phenomena can be separated from losses caused by experimental imperfections.