ELFT HÍRADÓ

[Szeminárium koordinátor <szfi-seminar AT wigner.mta.hu>]

SZFI Seminar
Zimborás Zoltán
(Wigner FK RMI, BME)
Mitigation of readout errors in near-term quantum devices with special 
emphasis on variational quantum optimization algorithms
We propose a scheme to reduce readout errors in experiments on quantum 
systems with finite number of measurement outcomes. Our method relies on 
performing classical post-processing which is preceded by Quantum Detector 
Tomography, i.e., the reconstruction of a Positive-Operator Valued Measure 
(POVM) describing the given quantum measurement device. If the measurement 
device is affected only by an invertible classical noise, it is possible to 
correct the outcome statistics of future experiments performed on the same 
device. To support the practical applicability of this scheme for near-term 
quantum devices, we characterize measurements implemented in IBM's and 
Rigetti's quantum processors. We find that for these devices, based on 
superconducting transmon qubits, classical noise is indeed the dominant 
source of readout errors. Moreover, we analyze the influence of the presence 
of coherent errors and finite statistics on the performance of our 
error-mitigation procedure. Applying our scheme on the IBM's 5-qubit device, 
we observe a significant improvement of the results of a number tasks 
including Quantum State Tomography, Quantum Process Tomography, the 
implementation of non-projective measurements, and certain quantum 
algorithms, such as Grover's search, the Bernstein-Vazirani algorithm. For 
more advanced variational quantum algorithms executed on a 15-qubit IBM 
device,  we introduce a correlated measurement noise model that can be 
efficiently parametrized and which admits noise mitigation on the level of 
marginal probability distributions. Characterization of the noise model can 
be done efficiently using a generalization of the Wilczek Quantum Overlapping 
Tomography. We observe numerically that for numerous variational quantum 
optimization algorithms the noise-mitigation radically improves the quality 
of the optimization.Tuesday, 20 October 2020, 10:00
video conference, https://letsmeet.wigner.hu/szeminarium
Language of the talk: English
All interested are welcome!
Róbert Juhászszfi-seminar AT wigner.mta.hu