Experimental Study Of The Dynamics Of Quantum Coherence In Solid-state Spin Systems

Quantum coherence roots from the superposition of quantum states and demonstrates the quantumness of a microsystem.It has been a research focus since the early days of quantum mechanics.Quantum coherence plays a significant role in the field of quantum information,especially in quantum computation.Long coherence time of quantum systems is one of the necessary conditions to realize universal quantum computing.Quantum coherence can be converted to quantum correlations in two-body or many-body quantum systems.Quantum correlations can be used as quantum resources and enable quantum computers to have computing power far exceeding that of classical computers.However,the coherence of quantum systems is easily affected by their environment,which causes decoherence of the quantum system,resulting in errors in the quantum computing procession.Therefore,investigation and protecting the coherence of quantum systems,including a single qubit system and many-body quantum systems,are particularly important for quantum computation.As a competing candidate for qubits,the solid-state spin system has many unique properties,for example,it is stable and can be controlled easily.Decoherence is one of the main reasons hindering its application in quantum computing.In order to protect the coherence of solid-state quantum systems,I carried out a series of experimental studies on quantum coherence based on magnetic molecular system and nitrogen-vacancy(NV)center in diamond in this thesis,including:1.Extension of the coherence time of the 1Cu magnetic molecular spin qubit to the order of milliseconds.By cooling,the interference of lattice vibration on the T1 time of the 1Cu magnetic molecular qubit was reduced.Then the coherence time of the qubit was extended to 1.4 ms through dynamical decoupling,which reaches the threshold condition for the coherence time of molecular spins qubits in quantum computation.2.Experimental measurement of the noise spectrum of the 1Cu magnetic molecular qubits and resolving the types of nuclear spins in its spin bath.We measured and analyzed the noise environment of the 1Cu molecular qubit based on noise spectroscopy.The noise spectrum of the environment was obtained and various nuclear spins in the environment were distinguished.This is helpful to further suppress the decoherence of the 1Cu molecular qubit.3.Experimental investigation of non-classical correlations in NV center solid-state spin system.Two-qutrit isotropic states were experimentally prepared and the existence of non-classical correlations beyond quantum entanglement was observed.The variation of quantum entanglement and quantum discord with the isotropic state parameter is also measured,and their monotonicity with the parameter is verified,as well as the difference of non-zero threshold of quantum entanglement between two-qutrit and two-qubit systems.This work lays the foundation for the subsequent protection and application of quantum correlation in quantum computing and promotes the research of high-dimensional quantum computation.