Theoretical study towards realization of measurement-based quantum computers

Hans J. Briegel, Dan E. Browne, Wolfgang Dür +2 more

アグン トゥリーサティアソ, AGUNG TRISETYARSO

Measurement-based quantum computation (MBQC) is a new exciting paradigm in the field of quantum computation, in which the quantum information processing is proceeded by the sequences of measurements on the logical qubits encoded in a highly entangled state.MBQC is considered to be one of the most realistic formats of quantum computer since it is more robust than the conventional reversible quantum computation protocols.However, there exists a number of challenges to overcome.This dissertation presents a theoretical study towards realization of measurement-based quantum computer using a single atom contained in a cavity as a qubit node.The control of coherence are achieved with the assistance of an externally applied classical field.An architecture for large number of qubits in a cluster state is also presented.The first half of this dissertation presents a technique to ensure the qubit coherency because the measurement over the cluster state needs to be performed on the coherently evolving qubits.Under this scheme, a cavity is irradiated concurrently with quantum and classical electromagnetic fields to manipulate the atomic population.It is shown theoretically that manipulation of the time evolution of the population of two states in cavity quantum electrodynamics (QED) is possible by introduction of an appropriate electromagnetic field.The theoretical justification is provided by the use of Darboux transformations on the potential in an one-dimensional stationary Dirac model.Here, Pauli matrices are the central parameters for controlling the collapse and revival of the Rabi oscillations.The second half of this dissertation presents a new architecture of MBQC.The circuit design and evaluation of a quantum carry-lookahead C.1 Maple codes for the modified atomic inversion. . . . . . . . . . . .C.2 Maple codes for the solution of D(σ 1 ). . . . . . . . . . . . . . . .C.3 Maple codes for the solution of D(σ 3 ). . . . . . . . . . . . . . . .C.4 Maple codes for the modified atomic inversion in the case of D(σ 2 ).C.5 The scheme for obtaining the correlations between atomic inversion and Dirac potentials. . . . . . . . . . .

Mark Tame, Robert Prevedel, Mauro Paternostro +3 more

We report the first experimental demonstration of an all-optical one-way implementation of Deutsch's quantum algorithm on a four-qubit cluster state. All the possible configurations of a balanced or constant function acting on a two-qubit register are realized within the measurement-based model for quantum computation. The experimental results are in excellent agreement with the theoretical model, therefore demonstrating the successful performance of the algorithm.

Tomoyuki Morimae

Robert Raussendorf

Daniel Volya, Prabhat Mishra

Surface codes provide a promising path towards large-scale fault-tolerant quantum computers. However, outside the difficulty in engineering qubits, their theoretical realization is hindered by a number of technical implementation details, including the initialization of an encoded quantum state on contemporary quantum computers. We propose a solution to overcome these challenges by utilizing recent theoretical developments in measurement-induced quantum steering. An encoded quantum state is prepared by repeatedly performing the following steps: (1) entangling qubits via a specifically chosen operation, (2) performing measurement on some of the qubits, and (3) resetting the measured qubits' states. We demonstrate our results using numerical simulations of surface codes, noting convergence of state fidelity, and commenting on choices for parameter selection.