Joint remote state preparation is a multiparty global quantum task in which several parties are assigned to jointly prepare a quantum state for a remote party. Although various protocols have been proposed so far, none of them are absolutely secure in the sense that the legitimate parties (the preparers plus the receiver) can by no means identify the state to be prepared even if they all collude with each other. | Communications in Physics, Vol. 23, No. 2 (2013), pp. 97-106 NONMAXIMAL ENTANGLEMENT CAN MAKE JOINT REMOTE STATE PREPARATION ABSOLUTELY SECURE CAO THI BICH AND NGUYEN BA AN Center for Theoretical Physics, Institute of Physics, Vietnam Academy of Science and Technology 10 Dao Tan, Ba Dinh, Hanoi, Vietnam Email: ctbich@; nban@ Received 01 April 2013; Accepted for publication 21 May 2013 Abstract. Joint remote state preparation is a multiparty global quantum task in which several parties are assigned to jointly prepare a quantum state for a remote party. Although various protocols have been proposed so far, none of them are absolutely secure in the sense that the legitimate parties (the preparers plus the receiver) can by no means identify the state to be prepared even if they all collude with each other. Here we resolve this drawback by employing the quantum channel in terms of nonmaximally entangled states whose parameters are kept secret to all the participants but used to split the information in a judicious way so that not only absolute security in the above-mentioned sense is achieved but also the performance is the simplest possible. I. INTRODUCTION Entanglement owns spooky action at distance and thus is a crucial resource in quantum information processing and quantum computing: it can be used to test fundamental laws of quantum physics, to provide unconditional security in quantum communication, to teleport unknown quantum states, to enhance capacity of quantum channels, to make inefficient algorithms efficient and so on (see, ., the book [1] and references therein). It was widely believed that global quantum operations are best performed via maximal entanglement, while utilization of nonmaximal entanglement is often regarded reluctant: a prior local filtering (Procrustean method) or a special procedure (entanglement distillation method) may need to be applied to probabilitically obtain a maximally entangled state from a .
