Igor Chełstowski | Searcharxiv

arXiv2025

Quantum Mycielskians: symmetries, twin vertices and distinguishing labelings

We investigate a quantum generalization of the Mycielski construction for quantum graphs. In particular, we analyze the quantum symmetries of quantum Mycielskians and their relation to the symmetries of the underlying quantum graphs. We introduce a quantum analogue of graphs with twin vertices and show that, for classical graphs with a small number of vertices, this notion reduces to the classical one. Finally, we propose a quantum extension of the distinguishing number and examine its behavior under the quantum Mycielski construction.

math.OA↗

arXiv2024

Operation fidelity explored by numerical range of Kraus operators

Present-day quantum devices require precise implementation of desired quantum channels. To characterize the quality of implementation one uses the average operation fidelity $F$, defined as the fidelity between an initial pure state and its image with respect to the analyzed operation, averaged over an ensemble of pure states. We analyze statistical properties of the operation fidelity for low-dimensional channels and study its extreme values and probability distribution, both of which can be used for statistical channel discrimination. These results are obtained with help of the joint numerical range of the set of Kraus operators representing a channel. Analytic expressions for the density $P\left(F\right)$ are derived in some particular cases including unitary and mixed unitary channels as well as quantum maps represented by commuting Kraus operators. Measured distributions of operation fidelity can be used to distinguish between two quantum operations.

quant-ph↗