Effects of stochastic noise on dynamical decoupling procedures

Dynamical decoupling is an important tool to counter decoherence and dissipation effects in quantum systems originating from environmental interactions. It has been used successfully in many experiments; however, there is still a gap between fidelity improvements achieved in practice compared to theoretical predictions. We propose a model for imperfect dynamical decoupling based on a stochastic Ito differential equation which could explain the observed gap. We discuss the impact of our model on the time evolution of various quantum systems in finite- and infinite-dimensional Hilbert spaces. Analytical results are given for the limit of continuous control, whereas we present numerical simulations and upper bounds for the case of finite control.Comment: 15 pages, 6 figure

Constructing Pauli pulse schemes for decoupling and quantum simulation

Dynamical decoupling is a powerful technique to suppress errors in quantum systems originating from environmental couplings or from unwanted inter-particle interactions. However, it can also be used to selectively decouple specific couplings in a quantum system. We present a simple and easy-to-use general method to construct such selective decoupling schemes on qubit and qudit networks by means of (generalized) Pauli operations. As these constructed schemes can suppress Hamiltonian interactions on general qudit networks selectively, they are well suited for purposes of approximate quantum simulation. Some examples are presented, demonstrating the use of our method and the resulting decoupling schemes.Comment: 11 pages, 5 figure

Pulse-controlled quantum gate sequences on a strongly coupled qubit chain

We propose a selective dynamical decoupling scheme on a chain of permanently coupled qubits with XX type interactions, which is capable of dynamically suppressing any coupling in the chain by applying sequences of local pulses to the individual qubits. We demonstrate that high-fidelity single- and two-qubit gates can be achieved by this procedure and that sequences of gates can be implemented by this pulse control alone. We discuss the applicability and physical limitations of our model specifically for strongly coupled superconducting flux qubits. Since dynamically modifying the couplings between flux qubits is challenging, they are a natural candidate for our approach.Comment: 10 pages, 7 figure

3D Engine for Game Carcassonne

Import 22/07/2015Cílem mé bakalářské práce je vytvořit 3D náhled na herní plochu hry Carcassonne. 3D náhled je implementovaný v jazyce Java, za podpory knihovny LWJGL, která poskytuje přístup k funkcím z grafické knihovny OpenGL. Práce je rozdělena na několik částí. V první části se věnuji popisu knihoven pro podporu tvorby grafiky v jazyce Java. Další část obsahuje zmínku o tvorbě 3D modelů. Poslední část se věnuje tvorbě samotného programu, problémům které při něm vznikly a dokumentaci programu. Má práce navazuje na existující bakalářkou práci, která řeší logiku a pravidla hry.The aim of my thesis is to create a 3D perspective on the game play area Carcassonne. 3D preview is implemented in Java, with the support of LWJGL library that provides access to the features of graphics library OpenGL. The work is divided into several parts. In the first part I describe libraries to support the creation of graphics in Java. Another section contains a reference to the creation of 3D models. The last part is dedicated to creating the program itself, the problems that occurred, and program documentation. My work builds on existing bachelor thesis, which manages game logic and rules.460 - Katedra informatikydobř