Effect of phase relaxation on quantum superpositions in complex collisions (original) (raw)
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2007
We study coherent superpositions of clockwise and anti-clockwise rotating intermediate complexes with overlapping resonances formed in bimolecular chemical reactions. Disintegration of such complexes represents an analog of famous double-slit experiment. The time for disappearance of the interference fringes is estimated from heuristic arguments related to fingerprints of chaotic dynamics of a classical counterpart of the coherently rotating complex. Validity of this estimate is confirmed numerically for the H+D2 chemical reaction. Thus we demonstrate the quantum-classical transition in temporal behavior of highly excited quantum many-body systems in the absence of external noise and coupling to an environment.
Macroscopic quantum superpositions in highly excited strongly interacting many-body systems
Physical Review C, 2003
We demonstrate a break-down in the macroscopic (classical-like) dynamics of wave-packets in complex microscopic and mesoscopic collisions. This break-down manifests itself in coherent superpositions of the rotating clockwise and anticlockwise wave-packets in the regime of strongly overlapping many-body resonances of the highly-excited intermediate complex. These superpositions involve ∼ 10 4 many-body configurations so that their internal interactive complexity dramatically exceeds all of those previously discussed and experimentally realized. The interference fringes persist over a time-interval much longer than the energy relaxation-redistribution time due to the anomalously slow phase randomization (dephasing). Experimental verification of the effect is proposed. PACS numbers: 25.70.Ef; 24.10.Cn; 24.60.Ky; 03.65.-w
Slow cross-symmetry phase relaxation in complex collisions
Physics of Atomic Nuclei, 2008
We discuss the effect of slow phase relaxation and the spin off-diagonal S-matrix correlations on the cross section energy oscillations and the time evolution of the highly excited intermediate systems formed in complex collisions. Such deformed intermediate complexes with strongly overlapping resonances can be formed in heavy ion collisions, bimolecular chemical reactions and atomic cluster collisions. The effects of quasiperiodic energy dependence of the cross sections, coherent rotation of the hyperdeformed ≃ (3 : 1) intermediate complex, Schrödinger cat states and quantum-classical transition are studied for 24 Mg+ 28 Si heavy ion scattering.
Effect of a finite-time resolution on Schrödinger cat states in complex collisions
Physics Letters B, 2005
We study the effect of finite time resolution on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy-ions, molecules and atomic clusters. It is shown that time averaging reduces the interference fringes acting effectively as dephasing. We propose a simple estimate of the "critical" time averaging interval. For the time averaging intervals bigger than the critical one the interference fringes wash out appreciably. This is confirmed numerically. We evaluate minimal energy intervals for measurements of the excitation functions needed to observe the Schrödinger Cat States. These should be easily observable in heavy-ion scattering. Such an experiment is suggested.
Quantum-classical correspondence in microscopic and mesoscopic complex collisions
Physical Review C, 2000
We propose a novel method to study quantum-classical correspondence in complex, e.g., heavy-ion, atomic, molecular, and atomic cluster collisions. The many-body rotating wave packets are formed spontaneously and their stability is due to the slow decoherence between highly excited strongly overlapping states of the intermediate complex. The phenomenon is illustrated by analyzing the 12 Cϩ 24 Mg collision. The significant deviations from the random-matrix theory are reproduced in terms of the macroscopically rotating molecule formed in this collision.
Decoherence for phase-sensitive relaxation
Journal of Luminescence, 2000
It is shown that the vibrational wave packet relaxation of initially coherent (displaced) states as well as the quantum superposition of coherent states in heat bathes with the different spectral densities exhibit a number of peculiarities compared with the cases of linear phase-sensitive relaxation, quadratic relaxation, and relaxational dynamics described with the use of Zurek's environmentally-induced pointer basis. A strong dependence of the relaxation rate on the position of the spectral density maximum of the bath is found. The differences can be used for the discrimination of the mechanisms of the molecule-environment interactions.
Observing a coherent superposition of an atom and a molecule
Physical Review A, 2006
We demonstrate that it is possible, in principle, to perform a Ramsey-type interference experiment to exhibit a coherent superposition of a single atom and a diatomic molecule. This gedanken experiment, based on the techniques of Aharonov and Susskind ͓Phys. Rev. 155, 1428 ͑1967͔͒, explicitly violates the commonly accepted superselection rule that forbids coherent superpositions of eigenstates of differing atom number. A Bose-Einstein condensate plays the role of a reference frame that allows for coherent operations analogous to Ramsey pulses. We also investigate an analogous gedanken experiment to exhibit a coherent superposition of a single boson and a fermion, violating the commonly accepted superselection rule forbidding coherent superpositions of states of differing particle statistics. In this case, the reference frame is realized by a multimode state of many fermions. This latter case reproduces all of the relevant features of Ramsey interferometry, including Ramsey fringes over many repetitions of the experiment. However, the apparent inability of this proposed experiment to produce well-defined relative phases between two distinct systems each described by a coherent superposition of a boson and a fermion demonstrates that there are additional, outstanding requirements to fully "liftЉ the univalence superselection rule.
How to observe a coherent superposition of an atom and a molecule
Phys Rev a, 2006
We demonstrate that it is possible, in principle, to perform a Ramsey-type interference experiment to exhibit a coherent superposition of a single atom and a diatomic molecule. This gedanken experiment, based on the techniques of Aharonov and Susskind [Phys. Rev. 155, 1428 (1967)], explicitly violates the commonly-accepted superselection rule that forbids coherent superpositions of eigenstates of differing atom number. This interference experiment makes use of a Bose-Einstein condensate as a reference frame with which to perform the coherent operations analogous to Ramsey pulses. We also investigate an analogous gedanken experiment to exhibit a coherent superposition of a single boson and a fermion, violating the commonly-accepted superselection rule forbidding coherent superpositions of states of differing particle statistics; in this case, the reference frame is realized by a multi-mode state of many fermions. This latter case reproduces all of the relevant features of Ramsey interferometry, including Ramsey fringes over many repetitions of the experiment. However, the apparent inability of this proposed experiment to produce well-defined relative phases between two distinct systems each described by a coherent superposition of a boson and a fermion demonstrates that there are additional, outstanding requirements to fully ``lift'' the univalence superselection rule.
Suppression of collisional decoherence by ultrafast molecular rotation
Using an optical centrifuge to control molecular rotation in extremely broad range of angular momenta, we study coherent rotational dynamics of nitrogen molecules in the presence of dissipation. Our detection technique of time- and frequency-resolved Raman scattering allows us to analyze the decay rate of rotational coherence as a function of the rotational quantum number between J=6J=6J=6 and J=66J=66J=66. We demonstrate that the rate of rotational decoherence can be varied by more than an order of magnitude in the studied range of JJJ values. The dependence of the decoherence rate on JJJ, pressure and temperature is in good agreement with the "energy corrected sudden" (ESC) model of collisional decay.
Overlapping resonances in the resistance of superposition states to decoherence
The Journal of Chemical Physics, 2010
Overlapping resonances are shown to provide new insights into the extent of decoherence experienced by a system superposition state in the regime of strong system-environment coupling. As an example of this general approach, a generic system comprising spin-half particles interacting with a thermalized oscillator environment is considered. We find that (a) amongst the collection of parametrized Hamiltonians, the larger the overlapping resonances contribution, the greater the maximum possible purity, and (b) for a fixed Hamiltonian, the larger the overlapping resonances contribution, the larger the range of possible values of the purity as one varies the phases in the system superposition states. Systems displaying decoherence free subspaces show that largest overlapping resonances contribution.