# Quantum Information Processing

## List of Papers (Total 110)

#### Noise resistance of activation of the violation of the Svetlichny inequality

In this paper, we analyze the activation of the violation of the Svetlichny inequality in GHZ states in the presence of noise. We take into account bit flip, phase flip, amplitude damping and depolarizing noisy channels acting on one, two or three qubits. We find that the effect is most robust in the case of phase flip while most fragile in the case of amplitude damping channel.

#### Entanglement-assisted quantum error-correcting codes over arbitrary finite fields

We prove that the known formulae for computing the optimal number of maximally entangled pairs required for entanglement-assisted quantum error-correcting codes (EAQECCs) over the binary field hold for codes over arbitrary finite fields as well. We also give a Gilbert–Varshamov bound for EAQECCs and constructions of EAQECCs coming from punctured self-orthogonal linear codes which...

#### Parity oblivious d-level random access codes and class of noncontextuality inequalities

The quantum ontological feature of contextuality apart from being central to foundations of quantum theory forms the basis of quantum advantage in a multitude of information processing tasks. In particular, the contextuality of preparation procedures was shown to power a particular two-party information processing task “parity oblivious multiplexing” (Spekkens et al. Phys Rev...

#### Entanglement access control for the quantum Internet

Quantum entanglement is a crucial element of establishing the entangled network structure of the quantum Internet. Here we define a method to achieve controlled entanglement access in the quantum Internet. The proposed model defines different levels of entanglement accessibility for the users of the quantum network. The path cost is determined by an integrated criterion on the...

#### Probing the geometry of two-qubit state space by evolution

We provide explicit geometric description of state manifolds obtained from evolution governed by a four-parameter family of time-independent Hamiltonians. We cover most cases related to the real interacting two-qubit systems and discuss possible types of evolutions in terms of the defining parameters. The relevant description of the pure state spaces and their Riemannian geometry...

#### Topological aspects of quantum entanglement

Kauffman and Lomonaco (New J Phys 4:73.1–73.18, 2002. arXiv:quant-ph/0401090, New J Phys 6:134.1–134.40, 2004) explored the idea of understanding quantum entanglement (the non-local correlation of certain properties of particles) topologically by viewing unitary entangling operators as braiding operators. In Alagic et al. (Yang–Baxter operators need quantum entanglement to...

#### Derivative of the disturbance with respect to information from quantum measurements

To study the trade-off between information and disturbance, we obtain the first and second derivatives of the disturbance with respect to information for a fundamental class of quantum measurements. We focus on measurements lying on the boundaries of the physically allowed regions in four information–disturbance planes, using the derivatives to investigate the slopes and...

#### Tomography from collective measurements

We discuss the tomography of N-qubit states using collective measurements. The method is exact for symmetric states, whereas for not completely symmetric states the information accessible can be arranged as a mixture of irreducible SU(2) blocks. For the fully symmetric sector, the reconstruction protocol can be reduced to projections onto a canonically chosen set of pure states.

#### Lorentz-covariant, unitary evolution of a relativistic Majorana qubit

We formulate a covariant description of a relativistic qubit identified with an irreducible set of quantum spin states of a Majorana particle with a sharp momentum. We treat the particle’s four-momentum as an external parameter. We show that it is possible to define an interesting time evolution of the spin density matrix of such a qubit. This evolution is manifestly Lorentz...

#### Security proof for round-robin differential phase shift QKD

We give a security proof of the ‘round-robin differential phase shift’ (RRDPS) quantum key distribution scheme, and we give a tight bound on the required amount of privacy amplification. Our proof consists of the following steps. We construct an EPR variant of the scheme. We show that the RRDPS protocol is equivalent to RRDPS with basis permutation and phase flips performed by...

#### Conditional entropic uncertainty relations for Tsallis entropies

The entropic uncertainty relations are a very active field of scientific inquiry. Their applications include quantum cryptography and studies of quantum phenomena such as correlations and non-locality. In this work we find entanglement-dependent entropic uncertainty relations in terms of the Tsallis entropies for states with a fixed amount of entanglement. Our main result is...

#### On the security of semi-device-independent QKD protocols

While fully device-independent security in (BB84-like) prepare-and-measure quantum key distribution (QKD) is impossible, it can be guaranteed against individual attacks in a semi-device-independent (SDI) scenario, wherein no assumptions are made on the characteristics of the hardware used except for an upper bound on the dimension of the communicated system. Studying security...

#### Two Gilbert–Varshamov-type existential bounds for asymmetric quantum error-correcting codes

In this note, we report two versions of Gilbert–Varshamov-type existential bounds for asymmetric quantum error-correcting codes.

#### Unitary equivalence classes of one-dimensional quantum walks II

This study investigated the unitary equivalence classes of one-dimensional quantum walks with and without initial states. We determined the unitary equivalence classes of one-dimensional quantum walks, two-phase quantum walks with one defect, complete two-phase quantum walks, one-dimensional quantum walks with one defect and translation-invariant one-dimensional quantum walks.

#### Quantum steering and entanglement in three-mode triangle Bose–Hubbard system

We consider the possibility of generation steerable states in Bose–Hubbard system composed of three interacting wells in the form of a triangle. We show that although our system still fulfills the monogamy relations, the presence of additional coupling which transforms a chain of wells onto triangle gives a variety of new possibilities for the generation of steerable quantum...

#### Allowed region and optimal measurement for information versus disturbance in quantum measurements

We present graphs of information versus disturbance for general quantum measurements of completely unknown states. Each piece of information and disturbance is quantified by two measures: (i) the Shannon entropy and estimation fidelity for the information and (ii) the operation fidelity and physical reversibility for the disturbance. These measures are calculated for a single...

#### Efficient classical simulation of the Deutsch–Jozsa and Simon’s algorithms

A long-standing aim of quantum information research is to understand what gives quantum computers their advantage. This requires separating problems that need genuinely quantum resources from those for which classical resources are enough. Two examples of quantum speed-up are the Deutsch–Jozsa and Simon’s problem, both efficiently solvable on a quantum Turing machine, and both...

#### Unitary reconstruction of secret for stabilizer-based quantum secret sharing

We propose a unitary procedure to reconstruct quantum secret for a quantum secret sharing scheme constructed from stabilizer quantum error-correcting codes. Erasure correcting procedures for stabilizer codes need to add missing shares for reconstruction of quantum secret, while unitary reconstruction procedures for certain class of quantum secret sharing are known to work without...

#### Authenticated communication from quantum readout of PUFs

Quantum readout of physical unclonable functions (PUFs) is a recently introduced method for remote authentication of objects. We present an extension of the protocol to enable the authentication of data: A verifier can check if received classical data were sent by the PUF holder. We call this modification QR-d or, in the case of the optical-PUF implementation, QSA-d. We discuss...

#### Three-player conflicting interest games and nonlocality

We outline the general construction of three-player games with incomplete information which fulfil the following conditions: (i) symmetry with respect to the permutations of players; (ii) the existence of an upper bound for total payoff resulting from Bell inequalities; (iii) the existence of both fair and unfair Nash equilibria saturating this bound. Conditions (i)–(iii) imply...