Skip to main content
2 of 2
added 256 characters in body
Narutaka OZAWA
  • 10.1k
  • 1
  • 42
  • 50

Your "countable separability" is called "countable decomposability" in [1]. As shown there, there exist separable but not countably decomposable states (in fact such states are dense as it is conjectured in [1]). Since every separable state on the tensor product of finite dimensional Hilbert spaces is finitely decomposable, your condition 1 does not imply 2.

See the MO post Is the set of separable quantum states closed? for some relevant discussion (and my goof).

[1] A. S. Holevo, M. E. Shirokov, R. F. Werner; Separability and Entanglement-Breaking in Infinite Dimensions. (https://arxiv.org/abs/quant-ph/0504204). See also (https://iopscience.iop.org/article/10.1070/RM2005v060n02ABEH000830).

Narutaka OZAWA
  • 10.1k
  • 1
  • 42
  • 50