Cite this problem as Problem 25.
Are two-way distillible entanglement and secret key rate lockable?
An entanglement measure is lockable, if it is extremely sensitive to the loss of a single qubit by one of the partners . In this paper it is shown that entanglement of formation, entanglement cost, logarithmic negativity, and all convex, asymptotically discontinuous entanglement measures are lockable. More recently , also squashed entanglement has been shown to be lockable.
 K. Horodecki, M. Horodecki, P. Horodecki, J. Oppenheim, Locking entanglement measures with a single qubit, quant-ph/0404096 (2004).
 M. Christandl, A. Winter, Uncertainty, Monogamy, and Locking of Quantum Correlations, quant-ph/0501090 (2005).