Decoherence of matter waves by thermal emission of radiation

Abstract

Emergent quantum technologies have led to increasing interest in decoherence -the processes that limit the appearance of quantum effects and turn them into classical phenomena. One important cause of decoherence is the interaction of a quantum system with its environment, which 'entangles' the two and distributes the quantum coherence over so many degrees of freedom as to render it unobservable. Decoherence theory [1][2][3][4] has been complemented by experiments using matter waves coupled to external photons [5][6][7] or molecules [8], and by investigations using coherent photon states [9], trapped ions [10] and electron interferometers [11,12]. Large molecules are particularly suitable for the investigation of the quantumclassical transition because they can store much energy in numerous internal degrees of freedom; the internal energy can be converted into thermal radiation and thus induce decoherence. Here we report matter wave interferometer experiments in which C 70 molecules lose their quantum behaviour by thermal emission of radiation. We find good quantitative agreement between our experimental observations and microscopic decoherence theory. Decoherence by emission of thermal radiation is a general mechanism that should be relevant to all macroscopic bodies.In this Letter we investigate the decoherence of molecular matter waves. We change the internal temperature of the molecules in a controlled way before they enter a near-field interferometer, and observe the corresponding reduction of the interference contrast. The idea behind this effort is to demonstrate a most fundamental decoherence mechanism that we encounter in the macroscopic world: All large objects, but also molecules of sufficient complexity, are able to store energy and to interact with their environment via thermal emission of photons. It is generally believed that warm macroscopic bodies emit far too many photons to allow the observation of de Broglie interferences, whereas individual atoms or molecules can be sufficiently well isolated to exhibit their quantum nature. However, there must be a transition region between these two limiting cases. Interestingly, as we show in this study, C 70 fullerene molecules have just the right amount of complexity to exhibit perfect quantum interference in our experiments [13] at temperatures below 1000 K, and to gradually lose all their quantum behaviour when the internal temperature is increased up to 3000 K. We can thus trace the quantum-to-classical transition in a controlled and quantitative way. The complexity of large molecules adds a novel quality with respect to previously performed experiments with atoms [5][6][7]: the energy in molecules may be equilibrated in many internal degrees of freedom during the free flight, and a fraction of the vibrational energy will eventually be reconverted into emitted photons. Therefore the internal dynamics of the molecule is also relevant for the quantum behaviour of the centre-of-mass state. In contrast to resonance fluorescence, which was investigated wit...

Decoherence of electron waves due to induced charges moving through a nearby resistive material

“…Compared to other experiments on decoherence [30], the present one has several advantages: It is conceptually very simple, it realizes an actually ohmic environment (as it was supposed in the first theoretical treatments of decoherence), the quantum object is a single free elementary particle (no inner degrees of freedom are involved -due to the absence of magnetic fields, spin is irrelevant in the present experiment), the interaction with the environment is due to the electric field of a charge (thus giving us an idea why the charge superselection rule is so powerful), and we get real 'pictures' of the transition from quantum to classical.…”

Основное Кинетическое Уравнение Для Приведенного Статистического Оператора Атома В Плазме

“…Предполагая, что при t → −∞ справедливо равен-ство (7), согласно которому переменные системы и термостата в далеком прошлом не запутаны, а зависящие от времени состояния термостата известны, можно вы-вести замкнутое уравнение эволюции для ρ S (t). Мы полагаем, что в уравнении (8) термостат не изменяется с течением времени, в частности, имеет место стационарное (равновесное) распределение: iL B ρ B = 0.…”

“…Для вывода уравнения Паули можно также исходить из неравновесного уравнения Лиувилля (8). Оно получается путем исполь-зования проекционных операторов, если в качестве релевантной части статистиче-ского оператора выбрать его диагональную часть [5].…”

Interferometry with large molecules: exploration of coherence, decoherence and novel beam methods

“…The corresponding work has already been published in great detail [13,[17][18][19]. We will therefore only briefly summarize the general idea of these experiments.…”