Quantum Crosstalk Cancellation And Quantum State Transfer In Superconducting Quantum Computers

Quantum computing is one of the hottest research directions at the moment,and its principle is to use quantum bits to complete computing tasks.Unlike the bits built by classical computers using digital circuits,thanks to their quantum physics properties,qubits can be at “0”and “1” at the same time.As the number of qubits increases,the amount of data in qubits is exponential increased.With the help of the superposition state properties of qubits,people can use quantum computers to solve problems that cannot be solved by classical computers,such as quantum many-body problems,decomposition of large numbers,etc.At present,the experimental platforms of quantum computing include: superconducting quantum platform,ion trap platform,optical quantum platform and semiconductor platform.Among them,the superconducting quantum platform,with its excellent scalability and controllability,is currently the most likely experimental platform for large-scale quantum computers capable of quantum error correction.To achieve this goal,scientists still need to solve many problems.In order to realize large-scale quantum computers that can realize quantum error correction,high-fidelity quantum gates need to be implemented first.In superconducting quantum platforms,the fidelity of quantum gates is mainly affected by the lifetime of the qubits(i.e.,the decoherence time),classical crosstalk during microwave manipulation,and quantum crosstalk due to coupling between qubits.In addition,limited by the conditions of the experimental equipment,such as the size of the working space of the dilution refrigerator,the number of qubits that a single superconducting quantum computer can accommodate is limited.If you want to reach the number of qubits on the order of millions,you need to build a network of quantum computers.The research content of this thesis mainly focuses on the above two problems.In the first half,we detail the basic concepts of superconducting quantum computing and the transmon type qubits currently used in mainstream superconducting quantum experiments.Taking quantum crosstalk as our research topic,we introduce the causes of quantum crosstalk and the existing solutions to eliminate quantum crosstalk.We delve into quantum crosstalk in Cross-Resonance gates and analyze the hardware parameter space for quantum crosstalk cancellation via microwave pulse control.In the second half,we introduce the stimulated adiabatic Raman passage(STIRAP)technique and the shortcut to adiabaticity(STA)technique based on the stimulated adiabatic Raman channel technique.Facing the problem of quantum state transfer between superconducting quantum computers.We propose a hardware framework using two hybrid optomechanical interfaces connected by continuous-mode fibers,and based on this hardware model,we propose a fast and high-fidelity quantum state transfer scheme.Compared with the ordinary STIRAP scheme,our scheme includes two STAs,which greatly improves the speed of quantum state transmission under the premise of ensuring high fidelity.