# Constant rotation of two-qubit equally entangled pure states by local quantum operations - Quantum Physics

Abstract: We look for local unitary operators $W 1 \otimes W 2$ which would rotate allequally entangled two-qubit pure states by the same but arbitrary amount. It isshown that all two-qubit maximally entangled states can be rotated through thesame but arbitrary amount by local unitary operators. But there is no localunitary operator which can rotate all equally entangled non-maximally entangledstates by the same amount, unless it is unity. We have found the optimal setsof equally entangled non-maximally entangled states which can be rotated by thesame but arbitrary amount via local unitary operators $W 1 \otimes W 2$, whereat most one these two operators can be identity. In particular, when $W 1 = W 2= i-\sqrt{2}{\sigma} x + {\sigma} y$, we get the local quantum NOToperation. Interestingly, when we apply the one-sided local depolarizing map,we can rotate all equally entangled two-qubit pure states through the sameamount. We extend our result for the case of three-qubit maximally entangledstate.

Author: Samir Kunkri, Swarup Poria, Preeti Parashar, Sibasish Ghosh

Source: https://arxiv.org/