Implementation of qubit reset for fixed-frequency transmons in tunable-coupler architectures

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dc.contributor.authorYan, Zixian
dc.contributor.departmentChalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2)sv
dc.contributor.departmentChalmers University of Technology / Department of Microtechnology and Nanoscience (MC2)en
dc.contributor.examinerBylander, Jonas
dc.contributor.supervisorChen, Liangyu
dc.contributor.supervisorTancredi, Giovanna
dc.date.accessioned2024-12-04T06:43:43Z
dc.date.available2024-12-04T06:43:43Z
dc.date.issued2024
dc.date.submitted
dc.description.abstractUnconditional and fast qubit reset is a key element to decrease algorithm computation time as the lifetime of the physical qubits continuously grows. For example, in quantum error correction (QEC), fast qubit reset in ancilla qubits is highly desired to accelerate the surface code algorithm. This thesis reports a qubit reset protocol utilizing a tunable coupler to transfer excitation from the qubit to the dedicated readout resonator in an architecture consisting of fixed-frequency transmons pairwise coupled by tunable couplers. The reset pulse is designed and optimized based on the Roland-Cerf protocol for resetting the |e⟩-state adiabatically in a two-level system (TLS) with an adiabatic pulse, demonstrating an improvement in reset fidelity compared to linear pulse in simulation. By changing the pulse shape, the evolution follows the shortcut-to-adiabaticity (STA) path within some parameter regions, enabling faster and better qubit reset. For resetting |f⟩-state, the numerical results also give adiabatic and STA pulse shapes similar to that given by the Roland-Cerf protocol in a two-level system, thus enabling us to model the |f⟩-state reset model as an approximate TLS system. We verify our theoretical prediction by running the reset protocols on a 25-qubit chip. The experiment results show fast reset operations while keeping low reset errors, verifying the validity of the proposed pulses [1]. However, the presence of other qubits limits the reset fidelity, and therefore, frequency separation between coupled qubits should be a parameter to be carefully considered at the design stage.
dc.identifier.coursecodeMCCX04
dc.identifier.urihttp://hdl.handle.net/20.500.12380/309017
dc.language.isoeng
dc.setspec.uppsokPhysicsChemistryMaths
dc.subjectquantum computing, superconducting circuit, adiabatic theorem
dc.titleImplementation of qubit reset for fixed-frequency transmons in tunable-coupler architectures
dc.type.degreeExamensarbete för masterexamensv
dc.type.degreeMaster's Thesisen
dc.type.uppsokH
local.programmeNanotechnology (MPNAT), MSc
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