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

Springer eBooks

Atomic “Bomb Testing”: The Elitzur–Vaidman Experiment Violates the Leggett–Garg Inequality

Carsten Robens, Wolfgang Alt, Clive Emary, Dieter Meschede, Andrea Alberti

Published Jan 1, 2018• 1 citation
Publisher

Abstract

Abstract Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the “bomb test” with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett–Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett–Garg inequality.

DOI
10.1007/978-3-319-64346-5_10

Related papers

Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality

Carsten Robens, W. Alt, Clive Emary +2 more

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the “bomb test” with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett–Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett–Garg inequality.

•Jan 1, 2017•0 citations

Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality

Carsten Robens, Wolfgang Alt, Clive Emary +2 more

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object-in a dramatic scenario, a bomb-without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the "bomb test" with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality-a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett-Garg inequality.

arXiv:1609.06218•Applied Physics B•Dec 19, 2016•59 citations

Atomic "bomb testing": The Elitzur-Vaidman experiment violates the Leggett-Garg inequality

Carsten Robens, Wolfgang Alt, Clive Emary +2 more

© The Author(s) 2018. Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object-in a dramatic scenario, a bomb-without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the 'bomb test' with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality-a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett-Garg inequality.

•Jan 3, 2018•0 citations

Testing Leggett–Garg inequality using Rydberg superatom

De-Sheng Xiang, Ren Liao, Biao Xu +14 more

Quantum mechanics predicts that measurement is inherently invasive, challenging the macrorealist view that physical properties exist independently of observation. The Leggett–Garg inequality (LGI) provides a test of this worldview, but its violation in systems in collective systems is often challenging due to technical measurement disturbance. By embedding an Elitzur–Vaidman interaction-free measurement (“quantum bomb-testing”) protocol into a microwave-driven Rydberg superatom (a mesoscopically coherent collective system) interferometer—we realize a high-fidelity, sequential measurement test. We observe a clear LGI violation that exceeds the classical bound by nearly 50 standard deviations in such a mesoscopic collective system. This result demonstrates the failure of noninvasive measurability for a collective quantum observable, establishing a scalable platform for probing temporal quantum correlations beyond the single-particle limit.

Advanced Photonics•Sep 11, 2026•0 citations

Quantum diffusion falsifies the concept of classical trajectories by violation of Leggett-Garg inequality

Carsten Robens, Wolfgang Alt, Dieter Meschede +2 more

When a physical object is in a quantum superposition, interference among the possible quantum paths affects the outcomes of a measurement. Gaining knowledge about the system with an intermediate measurement smears out, if not completely destroys, the resulting interference pattern. Based on this idea, Leggett and Garg formulated an inequality relating two-time correlation measurements, which establishes a quantitative criterion for discerning quantum superposition on a fundamental ground. Originally proposed to test realism of macroscopic physical objects, the inequality is here used to prove the non-classicality of the motion of a cesium atom, which propagates on a space-time discrete lattice. Making use of ideal negative measurements to test the atom's motion, we obtain a 6 sigma experimental violation of the Leggett-Garg inequality. From a broader perspective, our findings provide rigorous validation of the idea that quantum transport experiments cannot be interpreted in terms of classical trajectories.

•Apr 15, 2014•1 citation

Ideal Negative Measurements in Quantum Walks Disprove Theories Based on Classical Trajectories

Carsten Robens, Wolfgang Alt, Dieter Meschede +2 more

We report on a stringent test of the nonclassicality of the motion of a massive quantum particle, which propagates on a discrete lattice.Measuring temporal correlations of the position of single atoms performing a quantum walk, we observe a 6σ violation of the Leggett-Garg inequality.Our results rigorously excludes (i.e., falsifies) any explanation of quantum transport based on classical, well-defined trajectories.We use so-called ideal negative measurements-an essential requisite for any genuine Leggett-Garg test-to acquire information about the atom's position, yet avoiding any direct interaction with it.The interactionfree measurement is based on a novel atom transport system, which allows us to directly probe the absence rather than the presence of atoms at a chosen lattice site.Beyond the fundamental aspect of this test, we demonstrate the application of the Leggett-Garg correlation function as a witness of quantum superposition.Here, we employ the witness to discriminate different types of walks spanning from merely classical to wholly quantum dynamics.

arXiv:1404.3912•Physical Review X•Jan 20, 2015•172 citations
Abstract Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the “bomb test” with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett–Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett–Garg inequality.
Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the “bomb test” with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett–Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett–Garg inequality.
Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object-in a dramatic scenario, a bomb-without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the "bomb test" with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality-a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett-Garg inequality.
© The Author(s) 2018. Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object-in a dramatic scenario, a bomb-without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the 'bomb test' with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality-a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett-Garg inequality.
Quantum mechanics predicts that measurement is inherently invasive, challenging the macrorealist view that physical properties exist independently of observation. The Leggett–Garg inequality (LGI) provides a test of this worldview, but its violation in systems in collective systems is often challenging due to technical measurement disturbance. By embedding an Elitzur–Vaidman interaction-free measurement (“quantum bomb-testing”) protocol into a microwave-driven Rydberg superatom (a mesoscopically coherent collective system) interferometer—we realize a high-fidelity, sequential measurement test. We observe a clear LGI violation that exceeds the classical bound by nearly 50 standard deviations in such a mesoscopic collective system. This result demonstrates the failure of noninvasive measurability for a collective quantum observable, establishing a scalable platform for probing temporal quantum correlations beyond the single-particle limit.
When a physical object is in a quantum superposition, interference among the possible quantum paths affects the outcomes of a measurement. Gaining knowledge about the system with an intermediate measurement smears out, if not completely destroys, the resulting interference pattern. Based on this idea, Leggett and Garg formulated an inequality relating two-time correlation measurements, which establishes a quantitative criterion for discerning quantum superposition on a fundamental ground. Originally proposed to test realism of macroscopic physical objects, the inequality is here used to prove the non-classicality of the motion of a cesium atom, which propagates on a space-time discrete lattice. Making use of ideal negative measurements to test the atom's motion, we obtain a 6 sigma experimental violation of the Leggett-Garg inequality. From a broader perspective, our findings provide rigorous validation of the idea that quantum transport experiments cannot be interpreted in terms of classical trajectories.
We report on a stringent test of the nonclassicality of the motion of a massive quantum particle, which propagates on a discrete lattice.Measuring temporal correlations of the position of single atoms performing a quantum walk, we observe a 6σ violation of the Leggett-Garg inequality.Our results rigorously excludes (i.e., falsifies) any explanation of quantum transport based on classical, well-defined trajectories.We use so-called ideal negative measurements-an essential requisite for any genuine Leggett-Garg test-to acquire information about the atom's position, yet avoiding any direct interaction with it.The interactionfree measurement is based on a novel atom transport system, which allows us to directly probe the absence rather than the presence of atoms at a chosen lattice site.Beyond the fundamental aspect of this test, we demonstrate the application of the Leggett-Garg correlation function as a witness of quantum superposition.Here, we employ the witness to discriminate different types of walks spanning from merely classical to wholly quantum dynamics.