Abstract
Information switching and swapping seem to be fundamental elements of quantum communication protocols. Another crucial issue is the presence of entanglement and its level in inspected quantum systems. In this article, a formal definition of the operation of the swapping local quantum information and its existence proof, together with some elementary properties analysed through the prism of the concept of the entropy, are presented. As an example of the local information swapping usage, we demonstrate a certain realisation of the quantum switch. Entanglement levels, during the work of the switch, are calculated with the Negativity measure and a separability criterion based on the von Neumann entropy, spectral decomposition and Schmidt decomposition. Results of numerical experiments, during which the entanglement levels are estimated for systems under consideration with and without distortions, are presented. The noise is generated by the Dzyaloshinskii-Moriya interaction and the intrinsic decoherence is modelled by the Milburn equation. This work contains a switch realisation in a circuit form—built out of elementary quantum gates, and a scheme of the circuit which estimates levels of entanglement during the switch’s operating.
Highlights
The constant development of quantum computing manifests itself in a great number of works concerning the physical implementations of quantum computers and networks, and a wide range of algorithms is still evolving
We present an analysis of entropy and entanglement level during the operation of switching and swapping of two quantum states
We have presented the quantum information transfer with the use of SWAP operation and its practical application as a circuit realising the quantum switch
Summary
The constant development of quantum computing manifests itself in a great number of works concerning the physical implementations of quantum computers and networks, and a wide range of algorithms (e.g., in quantum machine learning) is still evolving. We present an analysis of entropy and entanglement level during the operation of switching and swapping of two quantum states. We utilise simulation techniques to trace the entanglement in a circuit of known quantum gates, which performs a controlled swapping operation. It should be mentioned that, the results presented in this article on entanglement changes, produced by the switch gate, provide another example of different entanglement levels generated by quantum gates. This phenomenon was studied in the context of controlled negation gates in [7]. In [12], the optimisation of circuits realising SWAP operation for qudits (generalised units of quantum information) is presented.
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