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:1311.5840

On an Atom-Interferometer Test of the Speed of Collapse of Wavefunctions in Relativistic Quantum Mechanics

Hans C. Ohanian

Published Nov 22, 2013• 0 citations
arXivHTMLPDF

Abstract

I propose to resolve the controversy over the speed of collapse of quantum-mechanical wavefunctions by means of an experimental test with a modified symmetric Mach-Zehnder atom interferometer, with non-intersecting, parallel, widely separated final beams. According to the conventional collapse scenario, the coherent twin-peak atomic wavefunction in the beams of the interferometer suffers an instantaneous collapse, at infinite speed, when the atom is captured by one of the two detectors at the ends of the beams, but it remains coherent until that instant. In contrast, according to the Hellwig-Kraus relativistic collapse scenario, the wavefunction collapses at the speed of light, backward in time along the past light cone of each detector. This leads to a premature collapse, or pre-collapse, which for a beam-to-beam separation of 3 m extends over a time span of 10 ns before arrival at the detectors. Within this time span the paired wavepackets in the two beams will be incoherent. The difference between the coherent wavepackets of the conventional scenario and the incoherent wavepackets of the relativistic scenario can be tested by probing the atomic beams with a transverse laser beam crossing them near the detectors. If the paired atomic wavepackets in the two beams are coherent, the light scattered by the two beams will also be coherent and generate a standing light wave in the space between the beams, with detectable interference fringes. If the paired wavepackets are incoherent, no such interference fringes will be generated, and the distribution of the scattered light will be that of two independent dipoles. The design parameters for this test seem to lie within reach of the techniques of atom interferometry.

DOI
10.48550/arxiv.1311.5840

Related papers

On the Possibility of Probing the Speed of Quantum Collapse

José Ignacio Orlicki

The instantaneous nature of quantum entanglement remains one of the most intriguing aspects of quantum mechanics. While the no-signaling theorem prohibits faster-than-light communication, the concept of a finite speed for the collapse of the quantum wavefunction has been a subject of philosophical debate. In this paper, we propose an experimental setup designed to test the speed of wavefunction collapse using entangled photon pairs over a distance of 10 km. By systematically varying the time delay between measurements and analyzing the resulting correlations, we aim to outline a method that could place bounds on the collapse speed without contradicting the no-signaling theorem. We argue that detecting a finite, possibly superluminal, speed of collapse could allow for maintaining realism and locality through high-speed remote synchronization, eliminating the need for hidden variables. We provide a detailed experimental design, including an algorithm and a Python implementation using the Cirq library to simulate the proposed experiment. Our goal is to motivate experimentalists to undertake this test, which could have profound implications for our understanding of quantum mechanics and the nature of reality.

•Apr 11, 2025•0 citations

Collapse of Probability Distributions in Relativistic Spacetime

Hans C. Ohanian

The collapse of a spatial probability distribution is triggered by a measurement at a given spacetime point. It is customarily assumed that this collapse occurs along an equal-time hypersurface, say, t = 0. However, such a naïve instantaneous collapse process is inconsistent with relativity, because the equal-time hypersurfaces of different inertial reference frames are different. The attempts at implementation of instantaneous collapse in several different reference frames then lead to violations of probability conservation and violations of the scalar character of the probability contained in given volume elements. This problem affects not only the Copenhagen interpretation of quantum mechanics, but also other interpretations in which it is still necessary to specify what changes in probabilities occur when and where in a manner consistent with relativistic spacetime geometry. In the 1980s Schlieder and Hellwig and Kraus proposed that collapse of the probability distribution along the past light cone of the measurement point avoids these difficulties and leads to a Lorentz-invariant collapse scenario. Their proposal received little attention and some negative criticisms. In this paper I argue that the proposed past-light cone collapse is not only reasonable, but is compelled by Lorentz invariance of probability conservation, and is equally valid for the spatial probability distributions in quantum mechanics and for those in a game of chance, for instance, the probability distribution for a game with playing cards scattered over some spatial region. I examine the objections that have been made to the past-light-cone collapse scenario and show that these objections are not valid. Finally, I propose two possible interferometer experiments that can serve as direct tests of past-light-cone collapse, one with an atom interferometer, and the other with a light interferometer.

arXiv:1703.00309•Mar 1, 2017•0 citations

On the Possibility of Probing the Speed of Quantum Collapse

José Ignacio Orlicki

The instantaneous nature of quantum entanglement remains one of the most intriguing aspects of quantum mechanics. While the no-signaling theorem prohibits faster-than-light communication, the concept of a finite speed for the collapse of the quantum wavefunction has been a subject of philosophical debate. In this paper, we propose an experimental setup designed to test the speed of wavefunction collapse using entangled photon pairs over a distance of 10 km. By systematically varying the time delay between measurements and analyzing the resulting correlations, we aim to outline a method that could place bounds on the collapse speed without contradicting the no-signaling theorem. We argue that detecting a finite, possibly superluminal, speed of collapse could allow for maintaining realism and locality through high-speed remote synchronization, eliminating the need for hidden variables. We provide a detailed experimental design, including an algorithm and a Python implementation using the Cirq library to simulate the proposed experiment. Our goal is to motivate experimentalists to undertake this test, which could have profound implications for our understanding of quantum mechanics and the nature of reality.

•Nov 5, 2024•0 citations

Collapse and revival of the fringe pattern in a multiple-beam atom interferometer

Martin Weitz, Tobias Heupel, Theodor W. Hänsch

We report on the observation of collapse and revival of the fringe pattern in a multiple-beam atom interferometer, when the drift time between the beam splitting processes is varied. The atomic beam splitters are realized with laser pulses pumping the atoms into velocity selective dark states. For small drift times, the interference signal shows the sharply peaked Airy function-like pattern characteristic for multiple-beam interference. The fringe pattern collapses for larger drift times due to a recoil phase shift increasing quadratically with the transverse atomic momentum. When the total interaction time reaches an integer multiple of the inverse two-photon recoil energy in frequency units, the original fringe pattern is revived.

Europhysics Letters (EPL)•Mar 10, 1997•13 citations

Coherence loss and revivals in atomic interferometry: a quantum-recoil analysis

M Davidović, Ángel S. Sanz, M Božić +1 more

The coherence effects induced by external photons coupled to matter waves inside a Mach–Zehnder three-grating interferometer are analyzed. Alternatively to atom–photon entanglement scenarios, the model considered here only relies on the atomic wavefunction and the momentum shift induced in it by the photon scattering events. A functional dependence is thus found between the observables, namely the fringe visibility and the phase shift, and the transversal momentum transfer distribution. Good quantitative agreement is found when comparing the results obtained from our model with the experimental data.

arXiv:1006.0450•Journal of Physics A Mathematical and Theoretical•Apr 4, 2012•3 citations

Finite-Speed-of-Light Effects in Atom Interferometry: Diffraction Mechanisms and Resonance Conditions

Christian Niehof, Daniel Derr, Enno Giese

Light-pulse atom interferometers serve as tools for high-precision metrology and are targeting measurements of relativistic effects. This development is facilitated by extended interrogation times and large-momentum-transfer techniques generating quantum superpositions of both interferometer arms on large distances. Due to the finite speed of light, diffracting light pulses cannot interact simultaneously with both arms, inducing phase perturbations that compromise the accuracy of the sensor -- an effect that becomes progressively important as spatial separations increase. For a consistent framework, we develop a theory for finite-speed-of-light effects in atom interferometers alongside with other relativistic effects such as the mass defect. Our analysis shows that their magnitude depends crucially on the diffraction mechanism and the specific interferometer geometry. We demonstrate that the velocity of the atomic cloud at the mirror pulse of a Mach-Zehnder interferometer is less critical than the precise tuning of the lasers for resonant diffraction. Finally, we propose an experiment to test our predictions based on recoilless transitions and discuss mitigation strategies to reduce the bias in gravimetric applications.

arXiv:2505.02728•May 5, 2025•0 citations
I propose to resolve the controversy over the speed of collapse of quantum-mechanical wavefunctions by means of an experimental test with a modified symmetric Mach-Zehnder atom interferometer, with non-intersecting, parallel, widely separated final beams. According to the conventional collapse scenario, the coherent twin-peak atomic wavefunction in the beams of the interferometer suffers an instantaneous collapse, at infinite speed, when the atom is captured by one of the two detectors at the ends of the beams, but it remains coherent until that instant. In contrast, according to the Hellwig-Kraus relativistic collapse scenario, the wavefunction collapses at the speed of light, backward in time along the past light cone of each detector. This leads to a premature collapse, or pre-collapse, which for a beam-to-beam separation of 3 m extends over a time span of 10 ns before arrival at the detectors. Within this time span the paired wavepackets in the two beams will be incoherent. The difference between the coherent wavepackets of the conventional scenario and the incoherent wavepackets of the relativistic scenario can be tested by probing the atomic beams with a transverse laser beam crossing them near the detectors. If the paired atomic wavepackets in the two beams are coherent, the light scattered by the two beams will also be coherent and generate a standing light wave in the space between the beams, with detectable interference fringes. If the paired wavepackets are incoherent, no such interference fringes will be generated, and the distribution of the scattered light will be that of two independent dipoles. The design parameters for this test seem to lie within reach of the techniques of atom interferometry.
The instantaneous nature of quantum entanglement remains one of the most intriguing aspects of quantum mechanics. While the no-signaling theorem prohibits faster-than-light communication, the concept of a finite speed for the collapse of the quantum wavefunction has been a subject of philosophical debate. In this paper, we propose an experimental setup designed to test the speed of wavefunction collapse using entangled photon pairs over a distance of 10 km. By systematically varying the time delay between measurements and analyzing the resulting correlations, we aim to outline a method that could place bounds on the collapse speed without contradicting the no-signaling theorem. We argue that detecting a finite, possibly superluminal, speed of collapse could allow for maintaining realism and locality through high-speed remote synchronization, eliminating the need for hidden variables. We provide a detailed experimental design, including an algorithm and a Python implementation using the Cirq library to simulate the proposed experiment. Our goal is to motivate experimentalists to undertake this test, which could have profound implications for our understanding of quantum mechanics and the nature of reality.
The collapse of a spatial probability distribution is triggered by a measurement at a given spacetime point. It is customarily assumed that this collapse occurs along an equal-time hypersurface, say, t = 0. However, such a naïve instantaneous collapse process is inconsistent with relativity, because the equal-time hypersurfaces of different inertial reference frames are different. The attempts at implementation of instantaneous collapse in several different reference frames then lead to violations of probability conservation and violations of the scalar character of the probability contained in given volume elements. This problem affects not only the Copenhagen interpretation of quantum mechanics, but also other interpretations in which it is still necessary to specify what changes in probabilities occur when and where in a manner consistent with relativistic spacetime geometry. In the 1980s Schlieder and Hellwig and Kraus proposed that collapse of the probability distribution along the past light cone of the measurement point avoids these difficulties and leads to a Lorentz-invariant collapse scenario. Their proposal received little attention and some negative criticisms. In this paper I argue that the proposed past-light cone collapse is not only reasonable, but is compelled by Lorentz invariance of probability conservation, and is equally valid for the spatial probability distributions in quantum mechanics and for those in a game of chance, for instance, the probability distribution for a game with playing cards scattered over some spatial region. I examine the objections that have been made to the past-light-cone collapse scenario and show that these objections are not valid. Finally, I propose two possible interferometer experiments that can serve as direct tests of past-light-cone collapse, one with an atom interferometer, and the other with a light interferometer.
The instantaneous nature of quantum entanglement remains one of the most intriguing aspects of quantum mechanics. While the no-signaling theorem prohibits faster-than-light communication, the concept of a finite speed for the collapse of the quantum wavefunction has been a subject of philosophical debate. In this paper, we propose an experimental setup designed to test the speed of wavefunction collapse using entangled photon pairs over a distance of 10 km. By systematically varying the time delay between measurements and analyzing the resulting correlations, we aim to outline a method that could place bounds on the collapse speed without contradicting the no-signaling theorem. We argue that detecting a finite, possibly superluminal, speed of collapse could allow for maintaining realism and locality through high-speed remote synchronization, eliminating the need for hidden variables. We provide a detailed experimental design, including an algorithm and a Python implementation using the Cirq library to simulate the proposed experiment. Our goal is to motivate experimentalists to undertake this test, which could have profound implications for our understanding of quantum mechanics and the nature of reality.
We report on the observation of collapse and revival of the fringe pattern in a multiple-beam atom interferometer, when the drift time between the beam splitting processes is varied. The atomic beam splitters are realized with laser pulses pumping the atoms into velocity selective dark states. For small drift times, the interference signal shows the sharply peaked Airy function-like pattern characteristic for multiple-beam interference. The fringe pattern collapses for larger drift times due to a recoil phase shift increasing quadratically with the transverse atomic momentum. When the total interaction time reaches an integer multiple of the inverse two-photon recoil energy in frequency units, the original fringe pattern is revived.
The coherence effects induced by external photons coupled to matter waves inside a Mach–Zehnder three-grating interferometer are analyzed. Alternatively to atom–photon entanglement scenarios, the model considered here only relies on the atomic wavefunction and the momentum shift induced in it by the photon scattering events. A functional dependence is thus found between the observables, namely the fringe visibility and the phase shift, and the transversal momentum transfer distribution. Good quantitative agreement is found when comparing the results obtained from our model with the experimental data.
Light-pulse atom interferometers serve as tools for high-precision metrology and are targeting measurements of relativistic effects. This development is facilitated by extended interrogation times and large-momentum-transfer techniques generating quantum superpositions of both interferometer arms on large distances. Due to the finite speed of light, diffracting light pulses cannot interact simultaneously with both arms, inducing phase perturbations that compromise the accuracy of the sensor -- an effect that becomes progressively important as spatial separations increase. For a consistent framework, we develop a theory for finite-speed-of-light effects in atom interferometers alongside with other relativistic effects such as the mass defect. Our analysis shows that their magnitude depends crucially on the diffraction mechanism and the specific interferometer geometry. We demonstrate that the velocity of the atomic cloud at the mirror pulse of a Mach-Zehnder interferometer is less critical than the precise tuning of the lasers for resonant diffraction. Finally, we propose an experiment to test our predictions based on recoilless transitions and discuss mitigation strategies to reduce the bias in gravimetric applications.