reconcile the principles of quantum mechanics with those of special relativity[@weibqft]. In quantum field theory, vanishing correlations for space-like separated operators are ensured[@weibqft]; whereas most efforts in quantum computation have so far relied upon non-relativistic quantum mechanics which is not fully compatible with Lorentz invariance and the causal structure of space-time. Recently however, several groups(see, for instance, Refs.[@milburn; @peres; @peres2; @adami; @ahn; @terashima; @solano; @czachorm; @milburn2; @terashima2; @molotkov; @rembielinski]) have focused their investigations on relativistic effects in quantum information science. The issues include Lorentz invariance of entanglement, the behaviour of Einstein-Podolsky-Rosen-Bell states in different inertial frames, and possible modifications to the degree of Bell inequality violations for moving observers[@czachor]. These relativistic effects may alter the efficiency of eavesdropper detection in quantum cryptography[@ekert3] and compromise the security of quantum protocols. It is also expected that future applications in quantum teleportation[@bennett4], entanglement-enhanced communication[@bennett], high-precision quantum clock synchronization based on shared entanglement, and quantum-enhanced positioning[@josza] will also require relativistic treatments of quantum systems; and in particular, the careful analysis of the properties of entangled particles under Lorentz transformations and the construction of meaningful measures of entanglement. In this article, we study the behaviour of Bell states under Lorentz transformations and consider von Neumann 