Joachim Ankerhold

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Based on an exact non-Markovian open systems quantum dynamics we demonstrate how to reduce the entropy of an open system through a cooperative effect of driving and dissipation. We illustrate the controlled dynamics in phase space in terms of Wigner functions and discuss the applicability of approximate approaches using master equations.
It is proposed to measure the current noise generated in a mesoscopic conductor by macroscopic quantum tunneling (MQT) in a current biased Josephson junction placed in parallel to the conductor. The theoretical description of this setup takes into account the complete dynamics of detector and noise source. Explicit results are given for the specific case of(More)
The tunnelling current in scanning tunnelling spectroscopy (STS) is typically and often implicitly modelled by a continuous and homogeneous charge flow. If the charging energy of a single-charge quantum sufficiently exceeds the thermal energy, however, the granularity of the current becomes non-negligible. In this quantum limit, the capacitance of the(More)
Standard optimal control methods perform optimization in the time domain. However, many experimental settings demand the expression of the control signal as a superposition of given waveforms. Since this type of constraint is not time-local, Optimal Control Theory cannot be used without modifications. Simplex methods, used as a substitute in this case, tend(More)
During the last few decades, the two fields of ultracold neutral atoms and of single trapped ions have undergone an amazing development. The incorporation of both these systems into a single experiment exploits the complementary physical properties of the subsystems and opens up novel lines of research. In this thesis, I present experimental results(More)
In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t 230402] that a combination of an exact stochastic decomposition of(More)
Motivated by recent experimental progress to readout quantum bits implemented in superconducting circuits via the phenomenon of dynamical bifurcation, transitions between steady orbits in a driven anharmonic oscillator, the Duffing oscillator, are analyzed. In the regime of weak dissipation a consistent diffusion equation in the semiclassical limit is(More)
Processes involving quantum tunneling can be found in a huge variety of physical and chemical systems, ranging in length from the mesoscopic scale of a few microns to the subatomic scale of a few fermi. It has been realized already three decades ago that thereby the interaction of the tunneling degree of freedom with environmental degrees of freedom plays a(More)
At low temperatures and strong friction the time evolution of the density distribution in position follows a quantum Smoluchowski equation. Recently, also higher-order contributions of quantum fluctuations to drift and diffusion coefficients have been systematically derived. As a nontrivial situation to reveal the impact of subleading quantum corrections(More)