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arXiv:1905.12248 · Chinese Physics Letters

Experimental Hamiltonian Learning of an 11-Qubit Solid-State Quantum Spin Register*

Pan‐Yu Hou, L. He, F. Wang, Xianzhi Huang, Wen-Yi Zhang, Xiaolong Ouyang, Xu Wang, Wentao Lian, X.-Y. Chang, Luming Duan

Published Oct 1, 2019• 15 citations
arXivHTMLPDF

Abstract

Learning the Hamiltonian of a quantum system is indispensable for prediction of the system dynamics and realization of high fidelity quantum gates. However, it is a significant challenge to efficiently characterize the Hamiltonian which has a Hilbert space dimension exponentially growing with the system size. Here, we develop and implement an adaptive method to learn the effective Hamiltonian of an 11-qubit quantum system consisting of one electron spin and ten nuclear spins associated with a single nitrogen-vacancy center in a diamond. We validate the estimated Hamiltonian by designing universal quantum gates based on the learnt Hamiltonian and implementing these gates in the experiment. Our experimental result demonstrates a well-characterized 11-qubit quantum spin register with the ability to test quantum algorithms, and shows our Hamiltonian learning method as a useful tool for characterizing the Hamiltonian of the nodes in a quantum network with solid-state spin qubits.

DOI
10.1088/0256-307x/36/10/100303

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Learning the Hamiltonian of a quantum system is indispensable for prediction of the system dynamics and realization of high fidelity quantum gates. However, it is a significant challenge to efficiently characterize the Hamiltonian which has a Hilbert space dimension exponentially growing with the system size. Here, we develop and implement an adaptive method to learn the effective Hamiltonian of an 11-qubit quantum system consisting of one electron spin and ten nuclear spins associated with a single nitrogen-vacancy center in a diamond. We validate the estimated Hamiltonian by designing universal quantum gates based on the learnt Hamiltonian and implementing these gates in the experiment. Our experimental result demonstrates a well-characterized 11-qubit quantum spin register with the ability to test quantum algorithms, and shows our Hamiltonian learning method as a useful tool for characterizing the Hamiltonian of the nodes in a quantum network with solid-state spin qubits.
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In this thesis, quantum states of single spin systems in solid state are investigated for potential applications in quantum information processing. The studied system is the nitrogen-vacancy defect in diamond, which can be thought of as a molecule trapped inside the diamond crystal. An issue for high-fidelity state preparation is the intitialization of the system. The photo-induced charge state dynamics of the nitrogen-vacancy defect is determined, and methods for charge state initialization are beeing developed. The electron spin state of single nitrogen-vacancy defects can be read out optically. Here, we focus on nearby nuclear spins coupled to the electron spin. We investigate the quantum evolution of a single nuclear spin, measurement of non-orthogonal quantum states and improved magnetic field sensing. Based on three nuclear spins, a small quantum register is realized. We prepare and measure the GHZ and the W state in this register, and implement an algorithm for quantum error correction.