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Rostock 2019 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 27: Quantum Information (Concepts and Methods) II

Q 27.7: Talk

Wednesday, March 13, 2019, 12:15–12:30, S HS 001 Chemie

Entanglement of truncated quantum states — •Giacomo Sorelli1, Vyacheslav N. Shatokhin1, Filippus S. Roux2, and Andreas Buchleitner11Physikalisches Institut, Albert-Ludwigs-Universität Freiburg i. Br. — 2National Metrology Institute of South Africa, Pretoria

Entanglement is a fundamental resource for many quantum information protocols. While many studies have been dedicated to bipartite entanglement of qubits, that of high-dimensional systems (qudits) is much less studied. Yet, qudits have higher information capacity and can enhance the security of quantum communication. In many practical cases, qudits are encoded in finite-dimensional subspaces of higher-dimensional Hilbert spaces. Then, after the dynamics populates the entire Hilbert space, the final state is often projected onto the encoding subspace. If the coupling between states inside and outside the encoding subspace is strong, such truncation can strongly affect the output state, and hence its entanglement.

We discuss the effect of truncation on the bipartite entanglement of n-level systems. They are initially prepared in a maximally-entangled state of m-dimensional subspaces HmHm of their total Hilbert spaces HnHn, and subsequently subjected to entanglement-preserving dynamics that populate all the n levels of each subsystem. We consider the truncation of this output state in a specific subspace HsHs (s<m) of the total Hilbert space. For random local unitary dynamics, we present simple expressions for the output state entanglement as a function of n, m and s.

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