Quantum Computing Asked on July 22, 2021
I am trying to formulate the calculation of conditional min-entropy as a semidefinite program. However, so far I have not been able to do so. Different sources formulate it differently. For example, in this highly influential paper, it has been formulated as:
$$H_{text{min}}(A|B)_rho = – underset{sigma_B} {text{inf}} D_{infty}(rho_{AB} | id_A otimes sigma_B)
$$
Where $$rho_{AB} in mathcal{H_A otimes H_B}, sigma in mathcal{H_B}$$ and
$$D_{infty}(tau | tau’) = text{inf} {lambda in
mathbb{R}: tau leq 2^{lambda} tau’ }$$
How do I formulate it into a semidefinite program? It is possible as is mentioned in this lecture.
A possible SDP program is given in Watrous’s lecture:
$$text{maximize}: <rho, X>$$
$$text{subject to}$$
$$Tr_X{X} == mathcal{1}_Y$$
$$X in text{Pos}(X otimes Y)$$
How do I write it in CVX or any other optimization system?
I think I have an answer. The following should be the CVX code for one of the formulations found in this link.
cvx_begin sdp
variable X(2, 2) hermitian
minimize(trace(id' * X)) % id is eye(2)
subject to
kron(id, X) >= rho_ab % the tensor product of two density matrices a, b
X >= 0
cvx_end
The optimal value found in this program is $$text{optval} = e^{-H_{text{min}}(A|B)}.$$ So simple calculation would solve for ${H_{text{min}}(A|B)}$. It turns out to be pretty simple at the end, given that the theoretical foundation leading up to this solution is not quite straightforward.
Answered by QuestionEverything on July 22, 2021
Get help from others!
Recent Questions
Recent Answers
© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP