자료유형  

 학위논문

Control Number  

0017161890

International Standard Book Number  

9798384453611

Dewey Decimal Classification Number  

540

Main Entry-Personal Name  

Yang, Zhibo.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of California, Berkeley., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

168 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-03, Section: B.

General Note  

Advisor: Whaley, K. Birgitta.

Dissertation Note  

Thesis (Ph.D.)--University of California, Berkeley, 2024.

Summary, Etc.  

요약Quantum computing has the potential to solve problems that are intractable for classical computers. In practice, physical qubits are coupled to their environments and are open quantum systems. To mitigate and correct environmental noises or utilize environmental degrees of freedom, one needs to carefully study the qubit properties in a open quantum system setting. In this thesis, we will first provide an overview of environmental couplings that are relevant to the quantum hardware of interest in the following chapters.We begin the main body of this thesis by introducing a robust control method for the implementation of quantum logic gates in superconducting devices. By switching between two time-constant Hamiltonians, single and two-qubit gates can be implemented with fidelity exceeding the threshold of most quantum error corrections codes in the presence of TLS bath and Markovian bath. This method is inspired by variational quantum algorithms (VQA), and we continue to study quantum machine learning (QML), which is a specific type of VQA, in the following chapter. We investigate the impact of dephasing on QML and show dephasing significantly lower image classification accuracy of QML models. However, we also reveal that increasing virtual bond dimension of QML networks by adding ancilla can improve the accuracy and adding two ancilla can mostly compensate for the accuracy loss due to dephasing.We then investigate qubits in open quantum system for quantum emulation. Specifically, we focus on the emulation of energy transfer between chromosomes in natural light-harvesting complexes using ion-trap quantum devices. This uphill energy transfer is assisted by vibrational modes in the molecules and is named vibration assisted energy transfer (VAET). We start with the study of VAET between two sites (qubits) coupled to one vibrational mode in the presence of classical white noise, which has the effect of dephasing. We show that in the weak noise regime, energy transfer is enhanced by VAET and harmed by the classical noise. In strong noise regime, the VAET signature is wiped out and the energy transfer efficiency will first increase with noise strength and then decrease to a quantum Zeno regime, a phenomenon termed as environment-assisted quantum transport (ENAQT). This is followed by the study of an expanded system with three sites coupled to two vibrational modes. We present a rich array of energy transfer processes. Among them, two phonon process associated to the mode coupled to the bridging site is found to have the greatest contribution to the energy transfer process. We also investigate the model in different scenarios, including varying coupling strength and temperature, presence of dephasing and coupled nodes, finding similar patterns but different relative energy transfer efficiencies. We then conclude with the impact of these studies on the application of near-term quantum devices.

Subject Added Entry-Topical Term  

Chemistry.

Subject Added Entry-Topical Term  

Quantum physics.

Subject Added Entry-Topical Term  

Physics.

Subject Added Entry-Topical Term  

Computational physics.

Index Term-Uncontrolled  

Open quantum systems

Index Term-Uncontrolled  

Quantum algorithms

Index Term-Uncontrolled  

Quantum computing

Index Term-Uncontrolled  

Quantum control

Index Term-Uncontrolled  

Virtual bond dimension

Added Entry-Corporate Name  

University of California, Berkeley Chemistry

Host Item Entry  

Dissertations Abstracts International. 86-03B.

Electronic Location and Access  

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Control Number  

joongbu:654566