Gan Qin

Quantum Adiabatic Algorithm for Factorization and Its Experimental Implementation

We propose an adiabatic quantum algorithm capable of factorizing numbers, using fewer qubits than Shors algorithm. We implement the algorithm in a NMR quantum information processor and experimentally factorize the number 21. In the range that our classical computer could simulate, the quantum adiabatic algorithm works well, providing evidence that the running time of this algorithm scales polynomially with the problem size.

Experimental demonstration of probabilistic quantum cloning.

The method of quantum cloning is divided into two main categories: approximate and probabilistic quantum cloning. The former method is used to approximate an unknown quantum state deterministically, and the latter can be used to faithfully copy the state probabilistically. Thus far, many approximate cloning machines have been experimentally demonstrated, but probabilistic cloning remains an experimental challenge, as it requires more complicated networks and a higher level of precision control. In this work, we design an efficient quantum network with a limited amount of resources and perform the first experimental demonstration of probabilistic quantum cloning in a NMR quantum computer. In our experiment, the optimal cloning efficiency proposed by Duan and Guo [Phys. Rev. Lett. 80, 4999 (1998)] is achieved.

Quantum Bertrand duopoly of incomplete information

We study Bertrands duopoly of incomplete information. It is found that the effect of quantum entanglement on the outcome of the game is dramatically changed by the uncertainty of information. In contrast with the case of complete information where the outcome increases with entanglement, when information is incomplete the outcome is maximized at some finite entanglement. As a consequence, information and entanglement are both crucial factors that determine the properties of a quantum oligopoly.

Stationary system of a two-level atom interacting with a single-mode phonon

We use three methods to calculate the ground state energy of the stationary system of a two-level atom interacting with a single-mode phonon. The results indicate that the variational method and the perturbation method are comparable to the exact power series solution in a wide parameter range. This might be useful for the time-dependent system

Persistent current in a mesoscopic semiconductor ring with electron-phonon interaction in the two-band model

We have studied, in the framework of the two-band lattice model, the persistent current in a one-dimensional mesoscopic semiconductor ring threaded by a flux , taking into consideration the electron-phonon interaction at absolute zero temperature. The current is a continuous function and periodic in , with a flux quantum , without jumps occurring when each period is over. The interband coupling enhances the current while the electron-phonon interaction suppresses it.

NEW VACUUM STATE AND SYMMETRY BREAKING IN POLARITON SYSTEM

Abstract The polariton system is studied in a concise approach using a simple model. A new ground state with negative energy is obtained and is found to exhibit symmetry breaking.