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A powerful experimental technique to study Efimov physics at positive scattering lengths is demonstrated. We use the Feshbach dimers as a local reference for Efimov trimers by creating a coherent superposition of both states. Measurement of its coherent evolution provides information on the binding energy of the trimers with unprecedented precision and yields access to previously inaccessible parameters of the system such as the Efimov trimers' lifetime and the elastic processes between atoms and the constituents of the superposition state. We develop a comprehensive data analysis suitable for noisy experimental data that confirms the trustworthiness of our demonstration.In few-body physics, the laws of quantum mechanics allow formation of peculiar loosely bound states [1]. Being insensitive to the details of the short range interparticle interactions, they display a variety of universal properties [2]. In recent years ultracold atoms have emerged as a main experimental platform to explore universality in few-body systems [3][4][5]. In the two-body domain, weakly bound dimers are now routinely used for the characterization of Feshbach resonances [6] and serve as the initial state for the production of ultra-cold molecules in their ro-vibrational ground state [7]. In the three-body domain, the captivating subject of Efimov physics has been explored in a variety of atomic systems [8][9][10][11][12][13][14][15][16][17][18]. But, interestingly, experimental techniques used in these explorations have been essentially limited to the study of inter-atomic inelastic processes, such as three-body recombination. Such an approach is best suited for the region of negative scattering lengths (a < 0), where trimers can be associated from the three atom continuum. In contrast, for positive scattering lengths (a > 0) the presence of dimers shifts the recombination related loss features into the atom-dimer continuum and Efimov resonances remain inaccessible for direct observation.One of the central results of experimental research reveals an intriguing universality in the absolute position of the Efimov three-body resonance across diverse openchannel-dominated Feshbach resonances [19] in a variety of atomic species [15,20,21]. The Efimov resonance's position is determined by the three-body parameter (3BP) which has generally been accepted to be system dependent, i.e. sensitive to the short-range physics. However, experimental results urged the theory to reinterpret the 3BP. Indeed, it was shown that this universality stems from the fact that atoms interact through a van der Waals potential which suppresses the probability to find the particles at short distances from each other [22][23][24][25][26][27]. The break-down of this universality has been predicted to occur only near closed-channel-dominated Feshbach resonances [28][29][30] which was confirmed in a recent experiment [18].The Efimov-van der Waals universality is well established for a < 0. However, for a > 0 the situation remains obscure due to the lack of reliable experi...

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