| Quantum computation and quantum information is a cross-discipline of quantum physics,computation science and communication.The quantum technology has advantaged on the faster information processing rate and larger information storage space.A quantum walk is the generation of a classical random walk and has been used to realize the quantum computation and design new quantum algorithms.Due to the quantum interference,the quantum walker can spread quadratic faster than the classical one.We propose and experimentally show that the spread velocity can be enhanced by choosing proper phase shift on the origin position.(1)We firstly calculate the position distribution and the spread velocity of the homogeneous and inhomogeneous quantum walks,respectively.Our calculations show that the features of the quantum walks depend on parameters of the coin and the phase shift on the origin position.The transport velocity is enhanced by increasing the coin parameter.Furthermore,we can enlarge the spread velocity by applying proper phase shift at the origin position.(2)We then experimentally realize the two different types of quantum walks,and the quantum superposition state with quadratic spread velocity are prepared.The horizontal and vertical polarization states of light are used to represent the two coin states.The different time of the light pulse arriving at the single photon detector by routing through distinct paths represent the positions of the walker.The coin parameter is changed by the oriented angle of the half-wave plate.The phase shift is achieved by an optical loop containing a fast phase electro-optic modulator which is controlled by the electrical pulse from the arbitrary wave generation.We measure the position probability distribution and the spread velocity.The experimental results agree well with the theoretical calculations.Our setup has the advantage on the stable and the scalability and pave the way for the realization of quantum computation based on the quantum walks. |
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