Frontiers of Mathematics in China >
A successive approximation method for quantum separability
Received date: 14 Jul 2011
Accepted date: 12 Dec 2012
Published date: 01 Dec 2013
Copyright
Determining whether a quantum state is separable or inseparable (entangled) is a problem of fundamental importance in quantum science and has attracted much attention since its first recognition by Einstein, Podolsky and Rosen [Phys. Rev., 1935, 47: 777] and Schröodinger [Naturwissenschaften, 1935, 23: 807-812, 823-828, 844-849]. In this paper, we propose a successive approximation method (SAM) for this problem, which approximates a given quantum state by a so-called separable state: if the given states is separable, this method finds its rank-one components and the associated weights; otherwise, this method finds the distance between the given state to the set of separable states, which gives information about the degree of entanglement in the system. The key task per iteration is to find a feasible descent direction, which is equivalent to finding the largest M-eigenvalue of a fourth-order tensor. We give a direct method for this problem when the dimension of the tensor is 2 and a heuristic cross-hill method for cases of high dimension. Some numerical results and experiences are presented.
Key words: Quantum system; entanglement; tensor; successive approximation; M-eigenvalue; cross-hill
Deren HAN , Liqun QI . A successive approximation method for quantum separability[J]. Frontiers of Mathematics in China, 2013 , 8(6) : 1275 -1293 . DOI: 10.1007/s11464-013-0274-1
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