Teleportation in an indivisible quantum system

Teleportation protocol is conventionally treated as a method for quantum state transfer between two spatially separated physical carriers. Recent experimental progress in manipulation with high-dimensional quantum systems opens a new framework for implementation of teleportation protocols. We show that the one-qubit teleportation can be considered as a state transfer between subspaces of the whole Hilbert space of an indivisible eight-dimensional system. We explicitly show all corresponding operations and discuss an alternative way of implementation of similar tasks.Comment: 4 pages, 1 figure, 1 tabl

Bidirectional imperfect quantum teleportation with a single Bell state

We present a bidirectional modification of the standard one-qubit teleportation protocol, where both Alice and Bob transfer noisy versions of their qubit states to each other by using single Bell state and auxiliary (trigger) qubits. Three schemes are considered: the first where the actions of parties are governed by two independent quantum random triggers, the second with single random trigger, and the third as a mixture of the first two. We calculate the fidelities of teleportation for all schemes and find a condition on correlation between trigger qubits in the mixed scheme which allows us to overcome the classical fidelity boundary of 2/3. We apply the Choi-Jamiolkowski isomorphism to the quantum channels obtained in order to investigate an interplay between their ability to transfer the information, entanglement-breaking property, and auxiliary classical communication needed to form correlations between trigger qubits. The suggested scheme for bidirectional teleportation can be realized by using current experimental tools.Comment: 8 pages, 4 figures; published versio

Symmetric blind information reconciliation and hash-function-based verification for quantum key distribution

We consider an information reconciliation protocol for quantum key distribution (QKD). In order to correct down the error rate, we suggest a method, which is based on symmetric blind information reconciliation for the low-density parity-check (LDPC) codes. We develop a subsequent verification protocol with the use of $\epsilon$-universal hash functions, which allows verifying the identity between the keys with a certain probability.Comment: 4 pages; 1 figure; published versio

Post-processing procedure for industrial quantum key distribution systems

We present algorithmic solutions aimed on post-processing for industrial quantum key distribution systems with hardware sifting. The main steps of the procedure are error correction, parameter estimation, and privacy amplification. Authentication of a classical public communication channel is also considered.Comment: 5 pages; presented at the 3rd International School and Conference "Saint-Petersburg OPEN 2016" (Saint-Petersburg, March 28-30, 2016

Information processing using three-qubit and qubit-qutrit encodings of noncomposite quantum systems

We study quantum information properties of a seven-level system realized by a particle in an one-dimensional square-well trap. Features of encodings of seven-level systems in a form of three-qubit or qubit-qutrit systems are discussed. We use the three-qubit encoding of the system in order to investigate subadditivity and strong subadditivity conditions for the thermal state of the particle. The qubit-qutrit encoding is employed to suggest a single qudit algorithm for calculation of parity of a bit string. Obtained results indicate on the potential resource of multilevel systems for realization of quantum information processing.Comment: 6 pages, 3 figures; published versio