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# Engineering and Control of Quantum Machines

Friday, 28th June 2019

Location: Technische Universität Berlin

Main building, Room H 3005

Straße des 17. Juni 135, 10623 Berlin

Guests are welcome!

# Programme

**Friday, 28. June 2019**

15:00 | PIQUE: a new Framework for Quantum Systems Engineering Prof. Archana Kamal, Umass Lowell, USA |

15:50 | Coffee Break |

16:10 | Reservoir Engineering using Quantum Optimal Control for Qubit Reset Daniel Basilewitsch, Universität Kassel |

16:35 | Quantum Simulation of non-Markovianity Using the Quantum Zeno Effect Sabrina Patsch, Universität Kassel |

17:00 | Informal get-together ("Stammtisch") |

# Abstracts

**PIQUE: a new Framework for Quantum Systems Engineering**

*Prof. Archana Kamal, Umass Lowell, USA*

High-fidelity quantum state preparation, manipulation and measurement are the three cornerstones of any quantum information processing platform. In this talk I will describe a new paradigm called PIQUE (for Parametrically-Induced QUantum Engineering), which tackles all three challenges in a unified framework employing parametrically-modulated interactions between quantum systems. In the first part of my talk, I will focus on how parametrically-induced interactions have stimulated new functionalities in the field of nonreciprocal amplification, and signal processing. In the second part of the talk, I will discuss how such interactions can be leveraged for quantum state engineering, specifically quantum ground state cooling, high-fidelity dissipative control and entanglement generation.

**Reservoir Engineering using Quantum Optimal Control for Qubit Reset **

*Daniel Basilewitsch, Uni Kassel *

We determine how to optimally reset a superconducting qubit which interacts with a thermal environment in such a way that the coupling strength is tunable. Describing the system in terms of a time-local master equation with time- dependent decay rates and using quantum optimal control theory, we identify temporal shapes of tunable level splittings which maximize the efficiency of the reset protocol in terms of duration and error. Time-dependent level splittings imply a modification of the system-environment coupling, varying the decay rates as well as the Lindblad operators. Our approach thus demonstrates efficient reservoir engineering employing quantum optimal control. We find the optimized reset strategy to consist in maximizing the decay rate from one state and driving non-adiabatic population transfer into this strongly decaying state.

** Quantum Simulation of non-Markovianity Using the Quantum Zeno Effect **

*Sabrina Patsch, Uni Kassel*

A watched quantum arrow does not move. This effect, referred to as the quantum Zeno effect, arises from a frequent measurement of a quantum system’s state. In more general terms, the evolution of the quantum system can be confined to a subspace of the system’s Hilbert space leading to quantum Zeno dynamics. Resulting from the measurement process, a source of dissipation is introduced into the systems dynamics. However, differently from a generic open quantum system, we can choose the strength of the dissipation by changing the parameters of the Zeno measurement. We capitalise on the property of tunable dissipation to create a quantum simulator for open quantum systems with Markovian and non-Markovian dynamics. We show how to tune the amount of dissipation and the non-Markovianity independently from each other and derive a Lindblad master equation to describe the evolution in the Markovian limit. We demonstrate the experimental feasibility of the proposed quantum simulator using a setup in the framework of cavity QED where the considered quantum system are photons inside a cavity being subject to an indirect measurement using circular Rydberg atoms.