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arXiv:quant-ph/0201138

Properties of multi-partite dark states

Pieter Kok, Kae Nemoto, William J. Munro

Published Jan 29, 2002• 3 citations
arXivHTMLPDF

Abstract

We investigate and define dark and semi-dark states for multiple qudit systems. For two-level systems, semi-dark and dark states are equivalent. We show that the semi-dark states are equivalent to the singlet states of the rotation group. They exist for many multiple qudit systems, whereas dark states are quite rare. We then show that when a dark state is collapsed onto another dark state of fewer parties, the resulting state is again dark. Furthermore, one can use two orthogonal multi-qudit dark states to construct a decoherence-free qudit.

DOI
10.48550/arxiv.quant-ph/0201138

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We investigate and define dark and semi-dark states for multiple qudit systems. For two-level systems, semi-dark and dark states are equivalent. We show that the semi-dark states are equivalent to the singlet states of the rotation group. They exist for many multiple qudit systems, whereas dark states are quite rare. We then show that when a dark state is collapsed onto another dark state of fewer parties, the resulting state is again dark. Furthermore, one can use two orthogonal multi-qudit dark states to construct a decoherence-free qudit.
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Abstract Based on the decoherence‐free states, two multi‐party semi‐quantum private comparison protocols are proposed to counteract collective noises. One can resist the collective‐dephasing noise well, and the other can resist the collective‐rotation noise. With the assistance of a semi‐honest third party (TP), multiple classical participants with restricted quantum abilities can compare their secret information by performing the proposed protocols once. It is manifested that the proposed protocols can resist both external attacks and internal attacks. Additionally, the operations in the multi‐party semi‐quantum private comparison protocols are simulated on the IBM Quantum Experience.
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Quantum entanglement is a fascinating topic with both theoretical and technological impacts. Yet, even in the simplest scenarios, there are still various open questions involving pure state and mixed state entanglement. Here we present the simplest entangled mixed states. We consider both qubits (quantum bits) and qudits (quantum digits). We first provide our simplest yet most important result for rank-2 bi-partite states, and we then generalize our results to go beyond rank-2 and to go beyond bi-partite states.