Quantum Brownian motion at strong dissipation probed by superconducting tunnel junctions

Abstract

We have studied the temporal evolution of a quantum system subjected to strong dissipation at ultra-low temperatures where the system-bath interaction represents the leading energy scale. In this regime, theory predicts the time evolution of the system to follow a generalization of the classical Smoluchowski description, the quantum Smoluchowski equation, thus, exhibiting quantum Brownian motion characteristics. For this purpose, we have investigated the phase dynamics of a superconducting tunnel junction in the presence of high damping. We performed current-biased measurements on the small-capacitance Josephson junction of a scanning tunneling microscope placed in a low impedance environment at milli-Kelvin temperatures. We can describe our experimental findings by a quantum diffusion model with high accuracy in agreement with theoretical predications based on the quantum Smoluchowski equation. In this way we experimentally demonstrate that quantum systems subjected to strong dissipation follow quasi-classical dynamics with significant quantum effects as the leading corrections.

5 pages, 4 figures

References in corpus (4)

• Many-Body Physics with Ultracold Gases
• The energy resolution function of a tunnel junction
• Critical Josephson current in the dynamical Coulomb blockade regime
• Probing the superconducting condensate on a nanometer scale

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• Phase Diffusion in Low-$E_J$ Josephson Junctions at milli-Kelvin Temperatures
• An entropy production based method for determining the position diffusion's coefficient of a quantum Brownian motion
• Fractional positional jumps in stochastic systems with tilted periodic double-well potentials
• The feedback driven atomic scale Josephson microscope