dorsal/arxiv
View SchemaTheory of quantum Loschmidt echoes
| Authors | Tomaz Prosen, Thomas H. Seligman, Marko Znidaric |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0304104 |
| URL | https://arxiv.org/abs/quant-ph/0304104 |
| DOI | 10.1143/PTPS.150.200 |
| Journal | Prog.Theo.Phys.Supp. 150 (2003), 200-228 |
Abstract
In this paper we review our recent work on the theoretical approach to quantum Loschmidt echoes, i.e. various properties of the so called echo dynamics -- the composition of forward and backward time evolutions generated by two slightly different Hamiltonians, such as the state autocorrelation function (fidelity) and the purity of a reduced density matrix traced over a subsystem (purity fidelity). Our main theoretical result is a linear response formalism, expressing the fidelity and purity fidelity in terms of integrated time autocorrelation function of the generator of the perturbation. Surprisingly, this relation predicts that the decay of fidelity is the slower the faster the decay of correlations. In particular for a static (time-independent) perturbation, and for non-ergodic and non-mixing dynamics where asymptotic decay of correlations is absent, a qualitatively different and faster decay of fidelity is predicted on a time scale 1/delta as opposed to mixing dynamics where the fidelity is found to decay exponentially on a time-scale 1/delta^2, where delta is a strength of perturbation. A detailed discussion of a semi-classical regime of small effective values of Planck constant is given where classical correlation functions can be used to predict quantum fidelity decay. Note that the correct and intuitively expected classical stability behavior is recovered in the classical limit, as the perturbation and classical limits do not commute. The theoretical results are demonstrated numerically for two models, the quantized kicked top and the multi-level Jaynes Cummings model. Our method can for example be applied to the stability analysis of quantum computation and quantum information processing.
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"abstract": "In this paper we review our recent work on the theoretical approach to\nquantum Loschmidt echoes, i.e. various properties of the so called echo\ndynamics -- the composition of forward and backward time evolutions generated\nby two slightly different Hamiltonians, such as the state autocorrelation\nfunction (fidelity) and the purity of a reduced density matrix traced over a\nsubsystem (purity fidelity). Our main theoretical result is a linear response\nformalism, expressing the fidelity and purity fidelity in terms of integrated\ntime autocorrelation function of the generator of the perturbation.\nSurprisingly, this relation predicts that the decay of fidelity is the slower\nthe faster the decay of correlations. In particular for a static\n(time-independent) perturbation, and for non-ergodic and non-mixing dynamics\nwhere asymptotic decay of correlations is absent, a qualitatively different and\nfaster decay of fidelity is predicted on a time scale 1/delta as opposed to\nmixing dynamics where the fidelity is found to decay exponentially on a\ntime-scale 1/delta^2, where delta is a strength of perturbation. A detailed\ndiscussion of a semi-classical regime of small effective values of Planck\nconstant is given where classical correlation functions can be used to predict\nquantum fidelity decay. Note that the correct and intuitively expected\nclassical stability behavior is recovered in the classical limit, as the\nperturbation and classical limits do not commute. The theoretical results are\ndemonstrated numerically for two models, the quantized kicked top and the\nmulti-level Jaynes Cummings model. Our method can for example be applied to the\nstability analysis of quantum computation and quantum information processing.",
"arxiv_id": "quant-ph/0304104",
"authors": [
"Tomaz Prosen",
"Thomas H. Seligman",
"Marko Znidaric"
],
"categories": [
"quant-ph",
"nlin.CD"
],
"doi": "10.1143/PTPS.150.200",
"journal_ref": "Prog.Theo.Phys.Supp. 150 (2003), 200-228",
"title": "Theory of quantum Loschmidt echoes",
"url": "https://arxiv.org/abs/quant-ph/0304104"
},
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