Two new deterministic secure quantum communication protocols are proposed in this paper. In these protocols, utilizing auxilians, no particle is transported between two authorized parties, who guarantee the safety of the protocols.
A three-party controlled deterministic secure quantum communication scheme through entanglement swapping is proposed firstly. In the scheme, the sender needs to prepare a class of Greenberger–Horne–Zeilinger (GHZ) states which are used as quantum channel. The two communicators may securely communicate under the control of the controller if the quantum channel is safe. The roles of the sender, the receiver, and the controller can be exchanged owing to the symmetry of the quantum channel. Different from other controlled quantum secure communication schemes, the scheme needs lesser additional classical information for transferring secret information. Finally, it is generalized to a multiparty controlled deterministic secure quantum communication scheme.
We propose a new protocol for deterministic secure quantum communication with a four-qubit W state. In this protocol, by using four local two-particle unitary operations and Bell basis measurements, the two legitimate users can directly transmit secret messages after exchanging some additional classical information. It will be shown that our protocol has a high capacity as each W state can carry two bits of secret information, and has a high intrinsic efficiency because almost all the instances are useful. Furthermore, this protocol is feasible with present day techniques.
In light of Lucamarini–Mancini's secure deterministic communication without entanglement [Phys. Rev. Lett94, (2005) 140501], by introducing an additional operation for encoding and additional classical information for decoding, we propose a new secure deterministic bidirectional communication protocol without using entanglement. In our protocol, two legitimate users can simultaneously exchange their different secret messages in a direct way with a set of communication devices. The proposed protocol is asymptotically secure in the limit of transmitting long messages.
A novel efficient scheme for deterministic secure quantum communication with cluster state is proposed. By utilizing Bell-basis- and [Formula: see text]-basis-measurements, the two legitimate users can directly transmit secret message after exchanging some additional classical information. It has a high capacity as each cluster state can carry two bits of information, and has a high intrinsic efficiency because almost all the instances are useful. Since the present scheme is based on the cluster state which is robust against decoherence, it is easily processed by a one-way quantum computer. Furthermore, this scheme is feasible with present-day technique.