Han Rong-Dian

Realization of the Fredkin Gate by Three Transition Pulses in a Nuclear Magnetic Resonance Quantum Information Processor

We have experimentally realized the Fredkin gate with only three transition pulses in a solution of alanine. It appears that no experimental realization of the Fredkin gate with fewer pulses has been reported yet. In addition, the simple structure of our scheme makes it easy to implement in experiments.

Multi-player and Multi-choice Quantum Game

We investigate a multi-player and multi-choice quantum game. We start from two-player and two-choice game and the result is better than its classical version. Then we extend it to N-player and N-choice cases. In the quantum domain, we provide a strategy with which players can always avoid the worst outcome. Also, by changing the value of the parameter of the initial state, the probabilities for players to obtain the best payoff will be much higher that in its classical version.We investigate a multi-player and multi-choice quantum game. We start from a two-player and two-choice game, and the result is better than its classical version. Then we extend this to N-player and N-choice cases. In the quantum domain, we provide a strategy with which players can always avoid the worst outcome. Also, by changing the value of the parameter of the initial state, the probabilities for players to obtain the best pay-off will be much higher than in its classical version.

Simulation of positron backscattering and implantation profiles using Geant4 code

For the proper interpretation of the experimental data produced in slow positron beam technique, the positron implantation properties are studied carefully using the latest Geant4 code. The simulated backscattering coefficients, the implantation profiles, and the median implantation depths for mono-energetic positrons with energy range from 1 keV to 50 keV normally incident on different crystals are reported. Compared with the previous experimental results, our simulation backscattering coefficients are in reasonable agreement, and we think that the accuracy may be related to the structures of the host materials in the Geant4 code. Based on the reasonable simulated backscattering coefficients, the adjustable parameters of the implantation profiles which are dependent on materials and implantation energies are obtained. The most important point is that we calculate the positron backscattering coefficients and median implantation depths in amorphous polymers for the first time and our simulations are in fairly good agreement with the previous experimental results.

Dependence of intrinsic defects in ZnO films on oxygen fraction studied by positron annihilation

Defects in ZnO films grown by radio-frequency reactive magnetron sputtering under variable ratios between oxygen and argon gas have been investigated by using the monoenergetic positron beam technique. The dominate intrinsic defects in these ZnO samples are O vacancies (V-O) and Zn interstitials (Zn-i) when the oxygen fraction in the O-2/Ar feed gas does not exceed 70% in the processing chamber. On the other hand, zinc vacancies are preponderant in the ZnO Elms fabricated in richer oxygen environment. The concentration of zinc vacancies increases with the increasing (2) fraction. For the oxygen fraction 85%, the number of zinc vacancies that could trap positrons will be smaller. It is speculated that some unknown defects could shield zinc vacancies. The concentration of zinc vacancies in the ZnO films varies with the oxygen fraction in the growth chamber, which is in agreement with the results of photoluminescence spectra.

Realization of the Three-Qubit Toffoli Gate in Molecules *

We present the experimental realization of this gate with a solution of chlorostyrene molecules. Our method does not depend heavily on the two-qubit controlled operation, which used to serve as the basic quantum operation in quantum computing. At present, we use transition operator that can be applied to all qubits in one operation. It appears that no experimental realization has yet been reported up to now regarding the implementation of quantum Toffoli gate using transition pulse on three-qubit nuclear magnetic resonance quantum computers. In addition, our method is experimentally convenient to be extended to more qubits.

Liquid Nuclear Magnetic Resonance Implementation of Quantum Computation in Subspace

Based on the logical labelling method, we prepare an effective pure state in a subsystem of a three spin system via liquid nuclear magnetic resonance technique. Then with this subspace effective pure state we implement the Deutsch-Jozsa algorithm. The tomography for the subspace effective pure state and the corresponding spectrum of the output for the Deutsch-Jozsa algorithm in a subsysytem of a nuclear spin system and demonstrated a subspace quantum computation.

Experimentally Obtaining the Likeness of Two Unknown Qubits on a Nuclear-Magnetic-Resonance Quantum Information Processor

We study the discrimination of quantum states from the other way around, i.e. the likeness of two quantum states. The fidelity is used to describe the likeness of two quantum states. Then we present a scheme to obtain the fidelity of two unknown qubits directly from the integral area of the spectra of the assistant qubit (spin) on a nuclear-magnetic-resonance quantum information processor. Finally, we demonstrate the scheme on a three-qubit quantum information processor. The experimental data are consistent with the theoretical expectation with an average error of 0.05, which confirms the scheme.Recently quantum states discrimination has been frequently studied. In this paper we study them from the other way round, the likeness of two quantum states. The fidelity is used to describe the likeness of two quantum states. Then we presented a scheme to obtain the fidelity of two unknown qubits directly from the integral area of the spectra of the assistant qubit(spin) on an NMR Quantum Information Processor. Finally we demonstrated the scheme on a three-qubit quantum information processor. The experimental data are consistent with the theoretical expectation with an average error of 0.05, which confirms the scheme.

Simulation of time bunching for a pulsed positron beam

Simulate anneal arithmetic has been used to settle the problem of time bunching on a pulsed slow-positron beam device. This paper has searched for the parameters of the device in a large scope and achieved the time resolution within 150ps at the target with accelerating voltage in a range of 0.5–30kV.

Vacancy in 6H-Silicon carbide studied by slow positron beam

The defect changes in 6H-SiC after annealing and 10MeV electron irradiation have been studied by using a variable-energy positron beam. It was found that after annealing, the defect concentration in n-type 6H-SiC decreased due to recombination with interstitials. When the sample was annealed at 1400°C for 30min in vacuum, a 20-nm thickness Si layer was found on the top of the SiC substrate, this is a direct proof of the Si atoms diffusing to surface when annealed at high temperature stages. After 10MeV electron irradiation, for n-type 6H-SiC, the S parameter increased from 0.4739 to 0.4822, and the relative positron-trapping rate was about 27.878 times of the origin sample, this shows that there are some defects created in n-type 6H-SiC. For p-type 6H-SiC, it is very unclear, this may be because of the opposite charge of vacancy defects.

Calculating the Relativistic Wave Functions of 11S0 and 13S1 Positronium

Based on the relativistic Bethe–Salpeter (BS) equation, the positronium wavefunctions in Euclidean momentum space are obtained. Meanwhile the energy levels of positronium ground states 11S0 and 13S1 are fitted to be 6.7934 eV and 6.7929 eV respectively, which qualitatively agree with the previous theoretical values. It is shown that the BS theory is valid and reliable to treat positronium.