Nature of Quantum Localization in Atomic Momentum Transfer Experiments.
نویسندگان
چکیده
Comment on " Nature of Quantum Localization in Atomic Momentum Transfer Experiments " In a recent Letter, Latka and West [1] claim that quantum suppression of atomic momentum transfer seen in recent experiments [2] is not due to dynamical localization (DL). We contend that their arguments proceed from a misunderstanding of both DL as well as aspects of the experiment. This is compounded by erroneous numerical results which invalidate their conclusions. DL is a global mechanism for quantum suppression of diffusion characterized by exponentially localized eigen-states or quasienergy states [3]. Even in paradigm systems like the standard map the localization length j can fluctuate substantially with the center of mass of the eigenstates, relative to the heuristic estimate. It is only in the limit of an asymptotically large stochasticity parameter that uniform DL occurs where the localization length j becomes insensitive to the peak position of the eigen-state. Away from this limit, DL is still a valid mechanism as long as the phase space is predominantly chaotic. Apparently , Latka and West misinterpret DL to mean only uniform DL. The experimental initial conditions [2] average the fluctuations in j. For certain parameter regimes that are predominantly chaotic, the final momentum distributions are in excellent agreement with the predictions of DL. Even in regimes with small regular regions, the evolution from our initial condition can develop exponential tails which are well described by DL. By contrast, if the overlap of the initial condition with the regular region is substantial, DL is not expected to apply as shown for l 3.8 in the latter paper in Ref. [2]. The role of the momentum boundary in the modulated standing wave is also not understood in Ref. [1]. Resonant kicks occur when the atomic velocity p matches the velocity of the standing wave l cos͑t͒. Thus, when p. p max l, the kicks turn off and momentum growth stops with important consequences. At l 1.52, though the classical phase space is chaotic, DL cannot be observed there because j exceeds p max , a feature which has to be considered in any bound system. In our system, a boxlike momentum distribution results which is shown and discussed in Ref. [2]. We have performed quantum simulations using both space-time integration and Floquet methods [2] for the parameters and initial conditions of Ref. [1]. The Floquet results provide the long-time averaged momentum distributions. …
منابع مشابه
Decoherence by spontaneous emission in atomic-momentum transfer experiments.
The influence of spontaneous emission on the dynamical localization in atomic momentum transfer observed in recent experiments is investigated. Our numerical and analytical results indicate that contrary to previous expectation quantum diffusion due to decoherence by spontaneous emission is non-negligible in the experimental regime and may actually be visible in the measured data. Modifications...
متن کاملDynamical localization of ultracold sodium atoms.
We report a study of atomic motion in time-dependent optical potentials. We measure momentum transfer in parameter regimes for which the classical dynamics are chaotic, and observe the quantum suppression of chaos by dynamical localization. The high degree of control over the experimental parameters enables detailed comparisons with theoretical predictions, and opens new avenues for investigati...
متن کاملAn experimental realization of the quantum δ-kicked rotor
We study experimentally quantum effects in atomic motion for a classically chaotic regime. A standing wave is pulsed on periodically in time, and the resulting atomic momentum is measured. Momentum grows diffusively until the quantum break time, after which dynamical localization is observed. Quantum resonances are observed for certain pulse durations.
متن کاملSLAC-PUB-454 July 1968 QUANTUM ELECTRODYNAMICS: THEOFY
At the last International High Energy Physics Conference in 1966 the speaker on this same topic of quantum electrodynamics concluded with these remarks: ‘IBy now I have strayed very far from the usual energy domain of 10mFIO eV for a high energy conference to 10Wg eV in discussing a missing few tenths of a MHz in the Lamb shift. In fact, both domains are important in probing the detailed behavi...
متن کاملThe Standard Model in Strong Fields: Electroweak Radiative Corrections for Highly Charged Ions
Electroweak radiative corrections to the matrix elements 〈ns1/2|ĤPNC|n′p1/2〉 are calculated for highly charged hydrogenlike ions. These matrix elements constitute the basis for the description of the most parity nonconserving (PNC) processes in atomic physics. The operator ĤPNC represents the parity nonconserving relativistic effective atomic Hamiltonian at the tree level. The deviation of thes...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Physical review letters
دوره 75 23 شماره
صفحات -
تاریخ انتشار 1995