Quantum Simulation Of Open System With Superconducting Circuits

With the rapid development of experimental techniques in recent years,quantum computation has transitioned from a theoretical model to physical realizations.Quantum computational advantages have been demonstrated in certain tasks through experimentation,attracting significant interest.Although these remarkable achievements are notable,there is still a long way to go before building a quantum computer with extremely low errors.However,due to its high scalability and flexible controllability,superconducting quantum computing represents one of the most promising techniques to date.This thesis focuses primarily on the quantum simulation of open systems using superconducting circuits.The document begins with an overview of the basic concepts of quantum computation and a review of the recent progress made in physical realizations of quantum computation and error correction.Furthermore,potential applications of quantum computation are discussed.Next,the focus shifts to superconducting quantum computing,where the design,control,readout and deocherence of a transmon qubit is detailed.This forms a fundamental basis for the discussion of quantum simulation based on superconducting circuits.Moreover,the crucial components of the measurement system in superconducting quantum computing are elaborated on,as they are key ingredients of multi-qubit experiments.We investigate the realization of discrete time crystal based on the fully connected superconducting quantum processor.We utilize two-photon driven-dissipative processes to observe the spontaneous breaking of time-translation symmetry and verify the existence of the time crystal by numerical simulations.The time crystal proposed in the thesis can be implemented by tuning the specified dissipation rates,which takes the inherent decoherence errors into consideration and suppress the effects of decoherence.Moreover,the engineered dissipation also enhances the robustness of the time crystal.Then we introduce the experimental observation of entanglement phase transition for mixed states,which is based on the contents in the second and third chapters.In this work,we construct pseudo-random circuits with global entangling gates of a fully connected superconducting processor to generate highly random quantum states.By the quantum state tomography of six qubits,we investigate the influences of enviornment on the entanglement between system qubits.The results demonstrate that our fully connected processor can efficiently generate highly random quantum states.The all-to-all architecture can decrease the depth of the circuit and lower decoherence errors.It is also the first time to observe the distribution of negativity spectrum in the experiment,which verifies the predication of the theory.Furthermore,we introduce the application and realization of nonunitary gates in the imaginary time evolution algorithm.Combined with the Grover’s algorithm,we improve the success probability and fidelity,and determine the ground state of a random Ising model.The nonunitary gates can also be employed in the circuits of digital simulation to reduce the depth.Finally,we introduce a work about the observation of multi-steady states in a ten-qubit one-dimension superconducting quantum processor with engineered noise.This work does not rely on the auxiliary qubits and measurements to simulate open systems.The techniques used in this work are also suitable to multiple qubits.The results obtained in this thesis lay the foundation for future research on novel physical phenomena in open quantum systems and non-Hermitian systems using superconducting quantum circuits.