Juju Hu

INVESTIGATION COMPARISON ON THE GATE SPEED OF THREE-LEVEL AND TWO-LEVEL QUANTUM NOT GATES WITH ASYMMETRIC POTENTIAL OF rf-SQUID

We investigate the relation between the speed of quantum NOT gate and the asymmetry or detuning of the potential in system of the interaction of a two-level rf-SQUID qubit with a classical microwave pulse. The rf-SQUID is characterized by an asymmetric double well potential that gives rise to diagonal matrix elements. Then in resonance, we compare the gate speeds for three-level and two-level quantum NOT gates. We show that in general, a three-level gate is much faster than the conventional two-level gate.

Fidelity of robust control in open quantum system with superconducting qubit

Superconducting quantum systems are promising candidates for quantum information processing due to their scalability and design flexibility. However, real quantum systems usually suffer from decoherence caused by environment disturbance. This effect, together with parametric error and un-modelled dynamics, usually leads to uncertainties in system models, which will destroy the systems excellent quantum properties. Therefore, it is significant to study robust control of open quantum system to enhance control performance in reality. In this paper, the control effect based on fidelity of the required robustness is defined using the concept of a sliding mode domain by considering uncertainties. Then, we design control scheme and acquire the corresponding analytical expression of sampling period based on data sampling. Meanwhile, we discuss the selection of sampling operator and quantum state drive in the process of quantum sampling. Furthermore, the influences of coupling constant, cut-off frequency and temperature on the sampling period are analysed.

Sampled-data design for decoherence control in open quantum system with operator errors

Application of quantum measurement to control system plays an important role in quantum information processing or other field. Since any real system must interact with surrounding environment, one has to consider the quantum measurement and control about open system. This paper investigates the problem of robustness for a single qubit with operator errors, which enlarges the field of quantum robustness control. It establishes control models on the basis of sliding mode control under Markovian noise, and defines control performance with indices as fidelity; coherence and purity that have real physical meanings. According to the different control targets, this paper presents the corresponding sliding mode design and the analytical expression of the data sampling period in a concrete Markovian environment. Furthermore, based on sampled-data control law, tracking the fidelity, coherence and purity of system and so on different state performance index, realizes the effective control of the operator error caused by the return of the coherent effect.

Simple edge detection method for vascular tree angiogram

Vascular tree angiogram is an important tool for computer-aided diagnosis on the vascular disease. The vascular edge detection in the angiogram is an important step in the angiogram analysis and computer-aided diagnosis, which is the basis on the segmentation of angiogram. This paper studies an improved edge detection method based on several classical methods. The experiments demonstrate the improved method has good performance in angiogram edge detection. This method is easy to be used in the processing of angiogram.