BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Liouvillian Tomography in Noisy Intermediate-scale Quantum Compute rs DTSTART:20241127T160000Z DTEND:20241127T180000Z DTSTAMP:20260622T023256Z UID:80739208-4f56-467d-a388-bd94a297d929 SEQUENCE:2 CREATED:20241122T154701Z DESCRIPTION:In the past four decades\, many exciting applications of quant um computers have been proposed. However\, the current noisy intermediate- scale quantum computers (NISQ) are severely limited by faulty gates and en vironmental interactions. To assess the role these factors play in qubit d ynamics\, Liouvillian tomography protocols were introduced as means of est imating the generator of the qubits’ Markovian evolution. In this work\, we propose a novel Liouvillian tomography technique that eliminates the c ommon Markovian assumption by considering a regression problem over deriva tives of Pauli string probability distributions. Additionally\, two compan ion algorithms for process and self-consistent state preparation and measu rement (SPAM) tomography are presented. All three tomographic procedures a re benchmarked with simulated data for systems of 1\,2 and 3 qubits. SPAM and process tomography were demonstrably capable of producing high-fidelit y estimates sufficient for the application of Liouvillian tomography. The retrieved Liouvillians were shown to match the target values\, at the leve l of the Hamiltonian\, dissipative rates\, and spectrum. Conversely\, the jump operators were observed to be more susceptible to noise\, resulting i n estimates that deviated from the target values. Liouvillian tomography i s then applied to two-qubit circuits in the Helmi quantum computer\, to re trieve the generator of the dynamics obtained when qubits are left to idle . Despite some limitations\, we believe this work marks an advancement in the field of Liouvillian tomography by providing the first protocol that c aptures non-Markovian dynamics. LAST-MODIFIED:20241122T155046Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/en/events/liouvillian-tomography-in-n oisy-intermediate-scale-quantum-computers/ X-ALT-DESC;FMTTYPE=text/html:

In the past four de cades\, many exciting applications of quantum computers have been proposed . However\, the current noisy intermediate-scale quantum computers (NISQ) are severely limited by faulty gates and environmental interactions. To as sess the role these factors play in qubit dynamics\, Liouvillian tomograph y protocols were introduced as means of estimating the generator of the qu bits’ Markovian evolution. In this work\, we propose a novel Liouvillian tomography technique that eliminates the common Markovian assumption by c onsidering a regression problem over derivatives of Pauli string probabili ty distributions.

Additionally\, two companion algorithms for pr ocess and self-consistent state preparation and measurement (SPAM) tomogra phy are presented. All three tomographic procedures are benchmarked with s imulated data for systems of 1\,2 and 3 qubits. SPAM and process tomograph y were demonstrably capable of producing high-fidelity estimates sufficien t for the application of Liouvillian tomography.

The retrieved L iouvillians were shown to match the target values\, at the level of the Ha miltonian\, dissipative rates\, and spectrum. Conversely\, the jump operat ors were observed to be more susceptible to noise\, resulting in estimates that deviated from the target values. Liouvillian tomography is then appl ied to two-qubit circuits in the Helmi quantum computer\, to retrieve the generator of the dynamics obtained when qubits are left to idle. Despite s ome limitations\, we believe this work marks an advancement in the field o f Liouvillian tomography by providing the first protocol that captures non -Markovian dynamics.

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