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Quantum superposition of distinct macroscopic states

Jonathan R. Friedman, Vijay Patel, W. Chen +2 more

NatureJul 1, 20001,158 citations

Superposition of macroscopically distinct states in quantum many-body systems

Tomoyuki Morimae

Jan 1, 20090 citations

Rapid and slow decoherence in conjunction with dissipation in a system of two-level atoms

Péter Földi, Attila Czirják, M. G. Benedict

We investigate the time evolution of the superposition of macroscopically distinct quantum states in a system of two-level atoms interacting with a thermal environment of photon modes. We show that the atomic coherent states are robust against decoherence; therefore, we call their superpositions atomic Schr\"odinger cat states. The initial fast regime of the time evolution is associated with the process of decoherence and it is directed toward the statistical mixture of the constituent coherent states of the original state for most of the initial conditions. However, certain superpositions, called symmetric, exhibit exceptionally slow decoherence. By introducing a new measure, we generalize the usual decoherence scheme regarding the evolution of the state to account also for the symmetric case. To stress the fact that the environment preserves symmetric superpositions much longer than the other ones, we present Wigner function images of the decoherence of a suitably oriented four-component cat state.We investigate the time evolution of the superposition of macroscopically distinct quantum states in a system of two-level atoms interacting with a thermal environment of photon modes. We show that the atomic coherent states are robust against decoherence; therefore, we call their superpositions atomic Schr\"odinger cat states. The initial fast regime of the time evolution is associated with the process of decoherence and it is directed toward the statistical mixture of the constituent coherent states of the original state for most of the initial conditions. However, certain superpositions, called symmetric, exhibit exceptionally slow decoherence. By introducing a new measure, we generalize the usual decoherence scheme regarding the evolution of the state to account also for the symmetric case. To stress the fact that the environment preserves symmetric superpositions much longer than the other ones, we present Wigner function images of the decoherence of a suitably oriented four-component cat state.

arXiv:quant-ph/0101072Physical Review AFeb 9, 200128 citations

Decoherence bypass of macroscopic superpositions in quantum measurement

Dominique Spehner, Fritz Haake

We study a class of quantum measurement models. A microscopic object is entangled with a macroscopic pointer such that a distinct pointer position is tied to each eigenvalue of the measured object observable. Those different pointer positions mutually decohere under the influence of an environment. Overcoming limitations of previous approaches we (i) cope with initial correlations between pointer and environment by considering them initially in a metastable local thermal equilibrium, (ii) allow for object–pointer entanglement and environment-induced decoherence of distinct pointer readouts to proceed simultaneously, such that mixtures of macroscopically distinct object–pointer product states arise without intervening macroscopic superpositions, and (iii) go beyond the Markovian treatment of decoherence.We study a class of quantum measurement models. A microscopic object is entangled with a macroscopic pointer such that a distinct pointer position is tied to each eigenvalue of the measured object observable. Those different pointer positions mutually decohere under the influence of an environment. Overcoming limitations of previous approaches we (i) cope with initial correlations between pointer and environment by considering them initially in a metastable local thermal equilibrium, (ii) allow for object–pointer entanglement and environment-induced decoherence of distinct pointer readouts to proceed simultaneously, such that mixtures of macroscopically distinct object–pointer product states arise without intervening macroscopic superpositions, and (iii) go beyond the Markovian treatment of decoherence.

arXiv:0709.0469Journal of Physics A Mathematical and TheoreticalFeb 5, 20085 citations

Macroscopic Superposition States in Isolated Quantum Systems

Roman V. Buniy, Stephen D. H. Hsu

arXiv:2011.11661Foundations of PhysicsJul 31, 20215 citations

Stable Macroscopic Quantum Superpositions

Florian Fröwis, Wolfgang Dür

We study the stability of superpositions of macroscopically distinct quantum states under decoherence. We introduce a class of quantum states with entanglement features similar to Greenberger-Horne-Zeilinger (GHZ) states, but with an inherent stability against noise and decoherence. We show that in contrast to GHZ states, these so-called concatenated GHZ states remain multipartite entangled even for macroscopic numbers of particles and can be used for quantum metrology in noisy environments. We also propose a scalable experimental realization of these states using existing ion-trap setups.We study the stability of superpositions of macroscopically distinct quantum states under decoherence. We introduce a class of quantum states with entanglement features similar to Greenberger-Horne-Zeilinger (GHZ) states, but with an inherent stability against noise and decoherence. We show that in contrast to GHZ states, these so-called concatenated GHZ states remain multipartite entangled even for macroscopic numbers of particles and can be used for quantum metrology in noisy environments. We also propose a scalable experimental realization of these states using existing ion-trap setups.

arXiv:1012.4472Physical Review LettersMar 16, 2011100 citations

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