BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Assessing Quantum Computers' Performance in the NISQ Era DTSTART:20241115T140000Z DTEND:20241115T160000Z DTSTAMP:20260630T225834Z UID:e28de3c4-a790-4c5d-b25d-c17230626a07 SEQUENCE:2 CREATED:20241108T155056Z DESCRIPTION:Quantum dynamics in the presence of an external environment ar e susceptible to decoherence and dissipation\, which are primary error sou rces in current quantum processors. The decay of quantum state fidelity — a measure of the correlation between the ideal and imperfect states — characterizes inevitable degradation in practical quantum processes. U nderstanding how this decay depends on the nature and severity of errors h elps in understanding decoherence and improving algorithms. However\, aver age fidelity decay overlooks significant dynamic aspects\, which this thes is aims to address. The first part examines fidelity decay in a random qua ntum circuit with errors from imperfect two-qubit gates and qubit permutat ions. We show that fidelity decays exponentially with both circuit depth a nd number of qubits raised to an architecture-dependent power\, and estima te decay rates based on the amplitude of the errors. These findings assist in benchmarking quantum computers using Quantum Volume - a figure of meri t for quantum processors - and suggest strategies for enhancing performanc e. In the second part\, we study how dissipation impacts chaotic and regul ar dynamics. We find that average fidelity decay does not differentiate ch aotic from regular systems\, so we analyze the spectral properties of diss ipative maps. By examining various regular dynamics\, we find that spectra l features unique to non-dissipative systems persist up to a dissipation t hreshold\, which can help distinguish between regular and chaotic maps. Th is thesis assists in characterizing error accumulation in quantum circuits and provides insights into the influence of noise in chaotic and regular quantum channels. LAST-MODIFIED:20241112T100856Z LOCATION:Sala P3 Pavilhão de Matemática\, Piso 1 URL:http://df.vps.tecnico.ulisboa.pt/en/events/assessing-quantum-computers -performance-in-the-nisq-era/ X-ALT-DESC;FMTTYPE=text/html:

Quantum dynamics in the presence of an external environment are susceptible to decoherence an d dissipation\, which are primary error sources in current quantum process ors. The decay of quantum state fidelity — a measure of the correlation between the ideal and imperfect states — characterizes inevitable degrad ation in practical quantum processes. Understanding how this decay depends on the nature and severity of errors helps in understanding decoherence a nd improving algorithms.

However\, average fidelity decay overlo oks significant dynamic aspects\, which this thesis aims to address. The f irst part examines fidelity decay in a random quantum circuit with errors from imperfect two-qubit gates and qubit permutations. We show that fideli ty decays exponentially with both circuit depth and number of qubits raise d to an architecture-dependent power\, and estimate decay rates based on t he amplitude of the errors.

These findings assist in benchmarkin g quantum computers using Quantum Volume - a figure of merit for quantum p rocessors - and suggest strategies for enhancing performance. In the secon d part\, we study how dissipation impacts chaotic and regular dynamics. We find that average fidelity decay does not differentiate chaotic from regu lar systems\, so we analyze the spectral properties of dissipative maps.
By examining various regular dynamics\, we find that spectral fea tures unique to non-dissipative systems persist up to a dissipation thresh old\, which can help distinguish between regular and chaotic maps. This th esis assists in characterizing error accumulation in quantum circuits and provides insights into the influence of noise in chaotic and regular quant um channels.

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