Experimental Study Of Quantum Systems With Noise In Nuclear Magnetic Resonance

Quantum information is a new subject based on physics and informatics.Quantum computing is one of the main branches of quantum information.According to quantum superposition and entanglement,quantum computing has an exponential increase in computing capacity and speed compared to classical computing.Due to its remarkable superiority,quantum computing has become very popular research fields.At present,the physical platforms for quantum computing include nuclear magnetic resonance system,superconducting system,quantum dot system,and so on.Among them,the NMR system has become one of the commonly used platforms for quantum computing and quantum simulation,because of its mature operation technology and long coherence time.Specifically,it is suitable for experimental research of small and medium-sized quantum systems.This thesis focuses on some intersting phenomena about quantum systems with noise and implements them in NMR systems.Firstly,the related principles and developments of quantum computing are briefly introduced.Then,the basic principles,experimental implementation and operation techniques,and pulse optimization methods of nuclear magnetic resonance quantum computing are introduced in detail,together with noise injection techniques,which are especially applied in my research work.The final part of this thesis is the two main research work:(1)In NMR system,the quantum simulation of photosynthesis energy transfer was realized.According to the quantum coherence theory,we have established an experimental scheme for effectively mimicking any spectral density of noise.The time-domain function of the Debye noise is obtained by using the principle of noise injection,and the pulse optimization method is applied to implement a simulation of the four-qubit photosynthesis energy transfer in the two-qubit system,whose computational complexity is lower than the hierarchical equation of motion.In addition,we use the Ramsey experiment to verify the Debye noise and derive the relevant theory in detail.(2)Noise-induced adiabaticity was realized on NMR experiments.Noise is not only a hindrance to the quantum system,but also it will promote the evolution of the quantum system to produce new phenomena.Theoretical work has shown that the addition of transverse relaxation white noise enhances or even induces adiabaticity.We implemented noise-induced adiabaticity in single and two qubit systems,and obtained adiabatic Hadamard gates and adiabatic entangled states.In particular,injection of the hybird noise was applied to achieving the evolution of single qubit time-varying Hamiltonian,which can be also used in other quantum systems.