Ancilla assisted quantum information processing general protocols and nmr implementations

Abstract

While a bit is the fundamental unit of binary classical information a qubit is a fundamental unit of quantum information In quantum information processing QIP it is customary to call the qubits under study as system qubits and the additionalqubits as ancillary qubits In this thesis I describe various schemes to exploit the ancillary qubits to e fficiently perform many QIP tasks and their experimental demonstrationsin nuclear magnetic resonance NMR systems Particularly we have showed that in the presence of suffi cient ancillary qubits it is possible to completely characterize a general quantumstate as well as a general quantum dynamics in a single measurement In addition it is also possible to exploit ancillary qubits for realizing noninvasive quantum measurements required for several experiments related to quantum physics Finally I will also illustrate some interesting applications of ancillary qubits in spectroscopy The abstracts of individual chapters are given below xContentsChapter 1 is the introduction to this thesis Here I describe about classical quantum information quantum information processing QIP nuclear magnetic resonance NMR NMR QIP and finally ancilla assisted QIP The standard method of Quantum State Tomography QST relies on the measurement of a set of noncommuting observables realized in a series of independent experiments Ancilla Assisted QST AAQST greatly reduces the number of independent measurements by exploiting an ancilla register in a known initial state In suitable conditions AAQST allowsmapping out density matrix of an input register in a single experiment In chapter 2 I describe methods for explicit construction of AAQST experiments in multi qubit registers I also report NMR implementations of AAQST on certain qubit systems and the experimental results confirm the e ffectiveness of AAQST in such many qubit registers In chapter 3 I present a procedure to characterize a general quantum process in a single newline newline