Quantum tunnelling in the hydrogen bond

Horsewill, A.J.

doi:10.1016/j.pnmrs.2007.09.002

Cited by 36 publications

(37 citation statements)

References 90 publications

(211 reference statements)

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“…We refer to these two approaches as the Pointer and Lindblad methods, respectively. The latter method in particular is well known and has been studied extensively for various systems [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]; the comparison between the two methods and the possibility of opening up an alternative way of looking at the system-environment interaction are the primary goals of this paper, in addition to the hunt for the AZE, which may be necessary for the warm, wet environments found in biological organisms to exhibit quantum behavior.…”

Section: Introductionmentioning

confidence: 99%

Environment-induced dephasing versus von Neumann measurements in proton tunneling

2014

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In this work we compare two theoretical approaches to modeling the action of the environment on an open quantum system. It is often assumed that as the temperature of the environment surrounding a quantum system increases, so does the speed of environment-induced dephasing, or decoherence (dynamical noise), and so the efficacy of processes such as quantum tunneling drops. An alternative way of viewing the action of the environment is to consider it as carrying out von Neumann-type measurements that, in the limit of continuous observation, lead to the so-called quantum Zeno effect, whereby the system is never allowed to evolve because its wave function is collapsed to its initial state with overwhelming likelihood. However, it has been established in recent years that under certain conditions quantum processes such as tunneling can actually be enhanced (thermally assisted) when the system couples to its environment, as this allows transitions to higher-energy eigenstates closer to the top of the potential barrier. Here we show that, over a specific temperature range, increasing the temperature of the heat bath to encourage such thermally induced tunneling is equivalent to increasing the frequency of a von Neumann-type measurement on the system by the environment (an anti-Zeno effect). However, this correspondence between these two independent pictures of quantum measurement breaks down above a certain limit: Increasing the frequency of measurement above this limit leads to a reversal from an anti-Zeno to a Zeno effect and the tunneling rate decreases again, whereas raising the temperature further leads to a leveling off in the tunneling probability.

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Section: Introductionmentioning

confidence: 99%

Environment-induced dephasing versus von Neumann measurements in proton tunneling

2014

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“…These have been reviewed in [7] so we shall only summarise the main results here. Consider two nuclear spin systems, labelled I and S, both with spin ½.…”

Section: Spin-lattice Relaxationmentioning

confidence: 99%

“…The relaxation is dominated by the modulation of the homonuclear and heteronuclear dipolar interactions and the elements of the relaxation matrix R ¼ q I r r q S are defined by correlation functions and spectral density functions given elsewhere [8,21]. Evaluating these for double proton transfer in the hydrogen bond we obtain for powder samples [7,13,23,24], …”

Section: Spin-lattice Relaxationmentioning

confidence: 99%

“…For fundamental investigations of the proton transfer process, solid-state NMR is well-suited to characterising the hydrogen dynamics [3][4][5][6][7]. The role of tunnelling can be a complex one so it is important to investigate model systems to gain fundamental insight into the proton transfer process as well as to provide a platform for a deeper exploration of the experimental protocols used to investigate the dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…1, where incoherent tunnelling is shown to dominate at low temperature. Here, NMR relaxometry has been particularly effective in characterising the dynamics and when the frequency and magnetic field domain is exploited through magnetic field-cycling, spin-lattice relaxation time measurements can provide highly accurate measurements of molecular correlation times and deep insight into the mechanisms of molecular motion [7,14,15].…”

Section: Introductionmentioning

confidence: 99%

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