M. Abdel-Aty

Efficient realization of quantum search algorithm using quantum annealing processor with dissipation

Following experimental work [Nature, 473, 194 (2011)10.1038/nature10012], we propose a new physical scheme for perfect implementation of a quantum search algorithm in the presence of qubits dissipation. It is shown that the Grover algorithm is obtained as a special case of the suggested quantum search algorithm. We have generated the quantum gates to realize the required steps for implementing the algorithm. Experimental evidence has been discussed in which, during a critical portion of quantum annealing, the qubits become entangled, and entanglement persists even as these systems reach equilibrium with a thermal environment. Our results provide an encouraging sign that quantum annealing is a viable technology for large-scale quantum computing. It is shown that the protocol can be successfully implemented within the present experimental limits.

Improving the quantum cost of NCT-based reversible circuit

We describe a scalable protocol for optimizing the quantum cost of the 3-bit reversible circuits built using NCT library. This technique takes into account a group theory approach. The algorithm analyzes the equivalent quantum circuits obtained by decomposing the reversible circuit to its elementary quantum gates and then applies optimization rules to reduce the number of the used elementary quantum gates. We apply the obtained algorithm using different quantum cost metrics that compare favorably with the relevant methods.

Squeezing dynamics of a nanowire system with spin-orbit interaction

We analyze the dynamics of squeezing in a ballistic quantum wire with Rashba spin-orbit interaction in the presence of both strong and weak magnetic fields and for different initial states of the system. Compared to the more standard measure of squeezing based on variances, we show that entropy squeezing is a more sensitive measure. Our results show that there is a strong relationship between the spin-orbit interaction and the strength of entropy squeezing. Furthermore, there is a relationship between the initial state and the number of squeezed components. This allows new knobs to control the strength and the component of entropy squeezing in a nanowire system.

Locality and classicality: role of entropic inequalities

The use of the so-called entropic inequalities is revisited in the light of new quantum correlation measures, specially nonlocality. We introduce the concept of classicality as the nonviolation of these classical inequalities by quantum states of several multiqubit systems and compare it with the nonviolation of Bell inequalities, that is, locality. We explore—numerically and analytically—the relationship between several other quantum measures and discover the deep connection existing between them. The results are surprising due to the fact that these measures are very different in their nature and application. The cases for

Analytical solution and applications of three qubits in three coupled modes without rotating wave approximation

n=2,3,4

Collapsing a Perfect Superposition to a Chosen Quantum State without Measurement

n=2,3,4 qubits and a generalization to systems with arbitrary number of qubits are studied here when discriminated according to their degree of mixture.

Robust general N user authentication scheme in a centralized quantum communication network via generalized GHZ states

We consider a multi-qubit system consisting of two trapped ions coupled in a laser field. The ions are identical three-level electronic systems which interact with one another through the phonon modes of their relative or center of mass motions, and the system is tuned so that two-phonon processes dominate the electronic transitions. The resulting evolution of the system is studied theoretically with a focus on the entanglement properties of the system. A method of quantifying the entanglement is discussed, and the time dependence of these quantifications is determined. The cases of the two ions coupled to the same phonon field and to two different isolated phonon fields are compared for Fock cavity modes. Instances of the entanglement sudden death recovery are identified in these various systems.

Entanglement of a nonlinear two two-level atoms interacting with deformed fields in Kerr medium

We study the dynamics of the three-qubit system interacting with multi-mode without rotating wave approximation (RWA). A physical realization of the system without direct qubits interactions with dephasing bath is proposed. It is shown that non-Markovian characters of the purity of the three qubits and the coupling strength of modes are stronger enough the RWA is no longer valid. The influences of the dephasing of qubits and interactions of modes on the dynamics of genuine multipartite entanglement and bipartite correlations of qubits are investigated. The multipartite and bipartite quantum correlations could be generated faster if we increase the coupling strength of modes and the RWA is not valid when the coupling strength is strong enough. The unitary transformations approach adopted here can be extended to other systems such as circuit or cavity quantum electrodynamic systems in the strong coupling regime.