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Dismantling Wave-Particle Duality with Quantum Cheshire Cat

Pratyusha Chowdhury, Arun Kumar Pati, Jing‐Ling Chen

Published Sep 1, 2020• 0 citations
OpenAlex

Abstract

The quantum Chesire cat has drawn quite a deal of attention over the past few years, challenging the common sense perception that a physical system is inseparable from its physical properties. In this work we propose a thought experiment based on the quantum Chesire cat, which shows that suitable pre- and post-selections can not only separate a physical system from its properties, but also even separate the wave and particle attributes of a physical system. The enduring view about the wave-particle duality has suggested that a quantum entity behaves like both a wave and a particle. However, the wave-particle duality can be spatially separated under such pre- and post-selection conditions, thus allowing us to dismantle these two fundamental attributes of nature.

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In a recent work, Aharonov et al suggested that a photon could be separated from its polarization in an experiment involving pre- and post-selection (Aharonov et al 2013 New J. Phys. 15 113015 ). They named the effect 'quantum Cheshire Cat', in a reference to the cat that is separated from its grin in the novel Alice ' s Adventures in Wonderland . Following these ideas, Denkmayr et al performed a neutron interferometric experiment and interpreted the results suggesting that neutrons were separated from their spin (Denkmayr et al 2014 Nat. Commun. 5 4492 ). Here we show that these results can be interpreted as simple quantum interference, with no separation between the quantum particle and its internal degree of freedom. We thus hope to clarify the phenomenon with this work, by removing these apparent paradoxes.

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The quantum Chesire cat has drawn quite a deal of attention over the past few years, challenging the common sense perception that a physical system is inseparable from its physical properties. In this work we propose a thought experiment based on the quantum Chesire cat, which shows that suitable pre- and post-selections can not only separate a physical system from its properties, but also even separate the wave and particle attributes of a physical system. The enduring view about the wave-particle duality has suggested that a quantum entity behaves like both a wave and a particle. However, the wave-particle duality can be spatially separated under such pre- and post-selection conditions, thus allowing us to dismantle these two fundamental attributes of nature.
Wave and particle are two fundamental properties of nature. The wave–particle duality has indicated that a quantum object may exhibit the behaviors of both wave and particle, depending upon the circumstances of the experiment. The major significance of wave–particle duality has led to a fundamental equation in quantum mechanics: the Schrödinger equation. At present, the principle of wave–particle duality has been deeply rooted in people’s hearts. This leads to a common-sense perception that wave property and particle property coexist simultaneously in a quantum entity, and these two physical attributes cannot be completely separated from each other. In classical physics, a similar common-sense thought is that a physical system is inseparable from its physical properties. However, this has been recently challenged and beaten by a quantum phenomenon called the “quantum Cheshire cat,” in which a cat and its grin can be spatially separated. In this work, we propose a thought experiment based on the technology similar to the quantum Cheshire cat. We find that wave and particle attributes of a quantum entity can be completely separated, thus successfully dismantling the wave–particle duality for a quantum entity. Our result is still consistent with the complementarity principle and deepens the understanding of quantum foundations.
Wave-particle duality is one of the most intriguing counterfactual concepts in quantum theory, describing how quantum entities exhibit both wave-like and particle-like behaviors. In classical intuition, physical properties are inseparable from their objective carriers, while for quantum entities, wave and particle attributes coexist simultaneously. However, recent studies on the Quantum Cheshire Cat phenomenon have shown that it is possible to separate a quantum object’s physical properties—including its wave and particle attributes—from the object itself in a microscopic system described by the two-state vector formalism. In this study, we propose a feasible scheme to spatially separate the wave and particle attributes of two entangled photons by carefully selecting pre- and post-selected states. Our scheme also ensures that the observation of the wave and particle attributes of the entangled photons always obeys Bohr’s complementarity principle.
Wave-particle duality is one of the most intriguing counterfactual concepts in quantum theory. In our common sense, the wave and particle properties of a quantum object are inseparable. However, the recent studies based on Quantum Cheshire Cat phenomena showed that separating the physical properties of a quantum object including wave and particle attributes from itself are possible in microscopic system described by two-state vector formalism. In this study, we put forward a feasible scheme to spatially separate the wave and particle attributes of two entangled photons by properly choosing the pre- and post-selection of path states. Our scheme also guarantees that the observation of wave and particle properties of the two entangled photons always obey the Bohr's complementarity principle.
As a fundamental characteristic of physical entities, wave‒particle duality describes whether a microscopic entity exhibits wave or particle attributes depending on the specific experimental setup. This assumption is premised on the notion that physical properties are inseparable from the objective carrier. However, after the concept of the quantum Cheshire cats was proposed, which makes the separation of physical attributes from the entity possible, the premise no longer holds. Furthermore, an experimental demonstration of the separation of the wave and particle attributes inspired by this scenario remains scarce. In this work, we experimentally separated the wave and particle attributes of a single photon by exploiting the quantum Cheshire cat concept for the first time. By applying a weak disturbance to the evolution of the system, we achieve an effect similar to the quantum Cheshire cat and demonstrated the separation of the wave and particle attributes via the extraction of weak values. Our work provides a new perspective for the in-depth understanding of wave‒particle duality and promotes the application of weak measurements in fundamentals of quantum mechanics.
In a recent work, Aharonov et al suggested that a photon could be separated from its polarization in an experiment involving pre- and post-selection (Aharonov et al 2013 New J. Phys. 15 113015 ). They named the effect 'quantum Cheshire Cat', in a reference to the cat that is separated from its grin in the novel Alice ' s Adventures in Wonderland . Following these ideas, Denkmayr et al performed a neutron interferometric experiment and interpreted the results suggesting that neutrons were separated from their spin (Denkmayr et al 2014 Nat. Commun. 5 4492 ). Here we show that these results can be interpreted as simple quantum interference, with no separation between the quantum particle and its internal degree of freedom. We thus hope to clarify the phenomenon with this work, by removing these apparent paradoxes.