Like cloning machine one can construct an approximate deletion machine also. an arbitrary quantum state against a copy cannot be perfectly deleted. Linearity of quantum mechanics put another restriction on deletion of an arbitrary quantum state i.e. Further, we have investigated the problem of secretly broadcasting of three-qubit entangled state between two distant partners. In this regard we have studied the broadcasting of entanglement using state dependent quantum cloning machine. Therefore broadcasting (cloning) of entanglement is a very important subject to study. Quantum entanglement is a very astonishing property in a multi-partite system and it is a very useful ingredient of quantum information theory.

We showed that this hybrid quantum cloning machine sometime gives better quality copy than the pre-existing quantum cloners. Therefore, we have constructed and studied a special kind of quantum cloning machine named as Hybrid quantum cloning machine which is nothing but a different combination of pre-existing quantum cloning machines. Although quantum mechanics forbid us to construct a perfect cloner, there is no restriction to construct an imperfect cloner. One such restriction is that we cannot copy an arbitrary quantum state. Quantum mechanics put restriction on performing some task which we can do classically. After that, in joint work with Andrew Landahl, I present a new set of procedures for performing logical operations called 'color-code lattice-surgery.' Finally, I describe a software package I developed for studying, developing, and evaluating quantum error-correcting codes under realistic noise. Next, I present a new stabilizer simulation algorithm that gives improved runtime performance for topological stabilizer codes. I then, in joint work with Ojas Parekh, analyze the performance of the quantum approximate optimization algorithm (QAOA) on a graph problem called Max Cut. I begin by presenting an overview of the language of quantum computation. For this reason, the focus of this dissertation is on the development of quantum-computing applications and robust, scalable quantum-architectures. Thus, the realization of large-scale, reliable quantum-computers will likely have a significant impact on the world. These speedups may enable quantum devices to solve currently intractable problems such as those in the fields of optimization, material science, chemistry, and biology. Quantum algorithms have the potential to provide exponential speedups over some of the best known classical algorithms.

No clone theorem