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 Buchleitner1 — 1Physikalisches 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 Hm⊗ Hm of their total Hilbert spaces Hn⊗ Hn, 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 Hs⊗ Hs (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.