Quantum Teleportation of a Three-qubit State using a Five-qubit Cluster State

We propose a scheme for cloning an arbitrary unknown two-qubit state and its orthogonal complement state with the assistance from the state preparer. Our scheme includes two stages. The first stage requires a quantum teleportation process, in which an arbitrary unknown two-qubit state can be deterministically teleported from the sender to the receiver with χ-type entangled states as the quantum channel. In the second stage, with the assistance of the state preparer, either a perfect copy or an orthogonal complement state of an arbitrary unknown two-qubit state can be obtained with a certain probability.

Generalized quantum state sharing of arbitrary unknown two-qubit state

We propose a new protocol of bidirectional and asymmetric quantum controlled teleportation, using a maximally seven-qubit entangled state as the quantum channel. That is to say Alice wants to transmit an arbitrary single qubit state (an arbitrary two-qubit state) to Bob and Bob wants to transmit an arbitrary two-qubit state (an arbitrary single state) to Alice via the control of the supervisor Charlie.

Using the five-qubit cluster state in a given entanglement structure as quantum channel, and employing some local operations and classical communication, a tripartite scheme for sharing a single-qubit operation on a remote target state is proposed. It has some obvious advantages; for example, the probability of success is 100%, i.e., it is deterministic, rather than probabilistic; the operation to be shared is arbitrary, other than restricted; the quantum and classical resource consumptions are relative economic, and the difficulty and intensity of the necessary operations are relatively low and small, while the intrinsic efficiency is higher than most existing QOS schemes, and so on. The underlying physical essence why the cluster state in the entanglement structure can be used to fulfill the task is revealed via deep studies. Besides, some concise discussions about the security are made and the experimental feasibility of the present theoretical scheme is analyzed.

We propose a scheme for asymmetric bidirectional controlled teleportation by using a six-qubit cluster state as quantum channel. In our scheme, Alice can transmit an arbitrary two-qubit entangled state to Bob and at the same time Bob can teleport an arbitrary single-qubit state to Alice under the control of the supervisor Charlie.

We propose two controlled remote state preparation protocols via partially entangled channels. One prepares a single-qubit state, and the other prepares a two-qubit state. Different from other controlled remote state preparation schemes which also utilize partially entangled channels, neither auxiliary qubits nor two-qubit unitary transformations are required in our schemes, and the success probabilities are independent of the coefficients of the quantum channel. The success probabilities are 50 and 25 % for arbitrary single-qubit states and two-qubit states, respectively. We also show that the success probabilities can reach 100 % for restricted classes of states.

The purpose of this paper is to explore how to teleport a low-dimensional (two-dimensional) arbitrary unknown two-qubit cat-like state through a high-dimensional entangled state constituting the quantum channel. We first present a scheme employing a maximally entangled three-qutrit state as the channel. Within this scheme, the sender performs a single-qubit projective measurement and a non-symmetric basis measurement on their particles. Based on these measurement outcomes, the receiver applies specific unitary operations to reconstruct the original cat-like state. Subsequently, the maximally entangled channel is replaced with a non-maximally entangled three-qutrit state. For this probabilistic teleportation scheme, the target state is reconstructed by introducing an auxiliary qubit and performing appropriate operations; the corresponding success probability is derived. Analysis indicates that the non-maximally entangled scheme generalizes the previous maximally entangled approach. Furthermore, both schemes are shown to be directly extendable to quantum channels formed by arbitrary high-dimensional entangled states.

We demonstrate that two independent spin-1/2 Ising-Heisenberg trimer chains provide an effective platform for the quantum teleportation of any entangled two-qubit state through the quantum communication channel formed by two Heisenberg dimers. The reliability of this quantum channel is assessed by comparing the concurrences, which quantify a strength of the bipartite entanglement of the initial input state and the readout output state. Additionally, we rigorously calculate quantities fidelity and average fidelity to evaluate the quality of the teleportation protocol depending on temperature and magnetic field. It is evidenced that the efficiency of quantum teleportation of arbitrary entangled two-qubit state through this quantum communication channel can be significantly enhanced by moderate magnetic fields. This enhancement can be attributed to the magnetic-fielddriven transition from a quantum antiferromagnetic phase to a quantum ferrimagnetic phase, which supports realization of a fully entangled quantum channel suitable for efficient quantum teleportation. The polymeric trimer chains Cu3(P2O6OH)2 are proposed as an experimental resource of this quantum communication channel, which provides an efficient platform for realization of the quantum teleportation up to moderate temperatures 40 K and extremely high magnetic fields 80 T.

We provide two schemes for tripartite Controlled Teleportation (CT) of an arbitrary two-qubit state by using five- and six-qubit cluster states as the quantum channel. It is found that the five-partite cluster state can be used for CT of an arbitrary two-qubit state with three agents and the six-partite cluster state can be used for symmetric CT scheme. In comparison with the similar scheme using the same quantum channels by Muralidharan and Panigrahi [Phys. Rev. A 78 (2008) 062333] and by Menona et al. [arXiv:/0906.3874v1], not multipartite entanglement measurements, which makes our schemes simpler than the existing schemes.

We consider the geometric global quantum discord (GGQD) of two-qubit systems. By analyzing the symmetry of geometric global quantum discord we give an approach for deriving analytical formulae of the extremum problem which lies at the core of computing the GGQD for arbitrary two-qubit states. Furthermore, formulae of GGQD of arbitrary two-qubit states and some concrete examples are presented.

We present a scheme for bidirectional controlled remote preparation of arbitrary single-qubit states by using a five-photon cluster-type state as the quantum channel. The arbitrary single-qubit states can be bidirectional remote prepared with only linear-optical elements under the controller’s control. The sender first transform the quantum channel to the target channel according to their knowledge of prepared states, then perform single-qubit measurements on their entangled particles, the controller performs a X-basis measurement and the receivers can prepared the original states on their entangled particles if they cooperate with the control. This scheme is more convenient in application since it only requires linear-optical elements for bidirectional controlled remote state preparation of single-qubit states with cluster-type states.

We analyze the optimal measurements accessing classical correlations in arbitrary two-qubit states. Two-qubit states can be transformed into the canonical forms via local unitary operations. For the canonical forms, we investigate the probability distribution of the optimal measurements. The probability distribution of the optimal measurement is found to be centralized in the vicinity of a specific von Neumann measurement, which we call the maximal-correlation-direction measurement (MCDM). We prove that for the states with zero-discord and maximally mixed marginals, the MCDM is the very optimal measurement. Furthermore, we give an upper bound of quantum discord based on the MCDM, and investigate its performance for approximating the quantum discord.

Non-Bell-pair quantum channel for teleporting an arbitrary two-qubit state

We study efficient quantum error correction schemes for the fully correlated channel on an n-qubit system with error operators that assume the form \(\sigma _x^{\otimes n}\), \(\sigma _y^{\otimes n}\), \(\sigma _z^{\otimes n}\). Previous schemes are improved to facilitate implementation. In particular, when n is odd and equals \(2k+1\), we describe a quantum error correction scheme using one arbitrary qubit \(\sigma \) to protect the data state \(\rho \) in a 2k-qubit system. The encoding operation \(\sigma \otimes \rho \mapsto \Phi (\sigma \otimes \rho )\) only requires 3k CNOT gates (each with one control bit and one target bit). After the encoded state \(\Phi (\sigma \otimes \rho )\) goes through the channel, we can apply the inverse operation \(\Phi ^{-1}\) to produce \({\tilde{\sigma }} \otimes \rho \) so that a partial trace operation can recover \(\rho \). When n is even and equals \(2k+2\), we describe a hybrid quantum error correction scheme using any one of the two classical bits \(\sigma \in \{|ij{\rangle }{\langle }ij|: i, j \in \{0,1\}\}\) to protect a 2k-qubit state \(\rho \) and two classical bits. The encoding operation \(\sigma \otimes \rho \mapsto \Phi (\sigma \otimes \rho )\) can be done by \(3k+2\) CNOT gates and a single-qubit Hadamard gate. After the encoded state \(\Phi (\sigma \otimes \rho )\) goes through the channel, we can apply the inverse operation \(\Phi ^{-1}\) to produce \(\sigma \otimes \rho \) so that a perfect protection of the two classical bits \(\sigma \) and the 2k-qubit state is achieved. If one uses an arbitrary two-qubit state \(\sigma \), the same scheme will protect 2k-qubit states. The scheme was implemented using MATLAB, Mathematica, Python and the IBM’s quantum computing framework qiskit.

Local correlations of mixed two-qubit states