In this paper, the realignment criterion and the RCCN criterion of separability for states in infinite-dimensional bipartite quantum systems are established. Let
HA and
HB be complex Hilbert spaces with
dimHA⊗HB=+∞. Let
ρ be a state on
HA⊗HB and
{δk} be the Schmidt coefficients of
ρ as a vector in the Hilbert space
C2(HA)⊗C2(HB). We introduce the realignment operation
ρR and the computable cross norm
∥ρ∥CCN of
ρ and show that, if
ρ is separable, then
∥ρR∥Tr=∥ρ∥CCN=k∑δk≤1. In particular, if
ρ is a pure state, then
ρ is separable if and only if
∥ρR∥Tr=∥ρ∥CCN=k∑δk=1.
By combining a parameterized Hermitian matrix, the realignment matrix of the bipartite density matrix, and the vectorization of its reduced density matrices, we present a family of separability criteria which are stronger than the computable cross-norm or realignment (CCNR) criterion. With linear contraction methods, the proposed criteria can be used to detect the multipartite entangled states that are biseparable under any bipartite partitions. Moreover, we show by examples that the presented multipartite separability criteria can be more efficient than the corresponding multipartite realignment criterion based on CCNR, multipartite correlation tensor criterion, and multipartite covariance matrix criterion.