Researches On Quantum Cloning And Quantum Deleting

There is no denying that we live in a world surrounded by information, quantum information has put forward great challenge to the orthodox information science. Quantum information is a field combination of quantum mechanics and information science. The science of quantum information processing is promising to have a significant impact on how we process information, solve algorithmic problems, engineer nano-scale devices and model fundamental physics. It is already changing the way we understand and control matter at the atomic scale, making the quantum world more familiar, accessible and understandable.Manipulation and extraction of quantum information are important tasks in building quantum computer. As we know, the copying and deleting of information in a classical computer are inevitable operations whereas similar operations cannot be realized perfectly in quantum computers. Quantum information has the unique property which we should treat it specially. Some aspects of quantum cloning and quantum deleting are studied in this paper, the result is the following1. We propose a feasible scheme to implement the 1 → 2 optimal cloning transformation for two pairs of orthogonal states of two-dimensional quantum systems in the context of cavity QED. The copied qubits are shown to be inseparable by using Peres-Horodecki criterion. We also present schemes to implement the 1 → 2 phase-covariant quantum cloning machine for input state in the x-y equator or x-z equator.2. A quantum state-dependent quantum deleting machine is constructed. We obtain a upper bound of the global fidelity on N-to-M quantum deleting from a set of K non-orthogonal states. Quantum networks are constructed for the above state-dependent quantum deleting machine when K=2. Our deleting protocol only involves a unitary interaction among the initial copies, with no ancilla. We also present some analogies between quantum cloning and deleting.3. We show that the universal Hadamard and Unitary gates could be implemented bya unitary evolution together with a measurement for any unknown state chosen from a set if and only if are linearly independent.