Optimal cloning and singlet monogamy.

Optimal asymmetric 1 → 4 quantum cloning in arbitrary dimension

We present an optimal asymmetric 1 → 4 quantum cloner. Our derivation generalizes the constructions of optimal asymmetric 1 → 2 and 1 → 3 quantum cloners in [Quantum Inf. Comput 5, 583 (2005)]. We explicitly prove the optimality of this cloner and give the maximum achievable fidelities. We also present the relation between the optimal quantum cloner with the multipartite entangled state which s...

Monogamy of Bell's inequality violations in nonsignaling theories.

We derive monogamy relations (tradeoffs) between strengths of violations of Bell's inequalities from the nonsignaling condition. Our result applies to general Bell inequalities with an arbitrary large number of partners, outcomes, and measurement settings. The method is simple, efficient, and does not require linear programing. The results are used to derive optimal fidelity for asymmetric clon...

Quantum cloning, Quantum Money, and Quantum Monogamy

Asymptotic quantum cloning is state estimation.

The impossibility of perfect cloning and state estimation are two fundamental results in quantum mechanics. It has been conjectured that quantum cloning becomes equivalent to state estimation in the asymptotic regime where the number of clones tends to infinity. We prove this conjecture using two known results of quantum information theory: the monogamy of quantum correlations and the propertie...

Better bounds on optimal measurement and entanglement recovery, with applications to uncertainty and monogamy relations

We extend the recent bounds of Sason and Verdú relating Rényi entropy and Bayesian hypothesis testing [arXiv:1701.01974] to the quantum domain and show that they have a number of different applications. First, we obtain a sharper bound relating the optimal probability of correctly distinguishing elements of an ensemble of states to that of the pretty good measurement, and an analogous bound for...