Quantum key distribution (QKD) protocols make it possible for two quantum parties to generate a secret shared key. Semiquantum (SQKD) protocols, such as "QKD with classical Bob" and Alice" (that have both been proven robust), achieve this goal even if one of the is classical. However, existing SQKD are not experimentally feasible current technology. Here we suggest new protocol, "Classical Alice controllable mirror", that can be implemented technology (using 4-level systems instead qubits),...

Semiquantum key distribution (SQKD) allows two parties (Alice and Bob) to create a shared secret key, even if one of these (say, Alice) is classical.However, most SQKD protocols suffer from severe practical security problems when implemented using photons.The recently developed "Mirror protocol" [1] an experimentally feasible protocol overcoming those drawbacks.The Mirror was proven robust (namely, it secure against limited class attacks including all noiseless attacks), but its in case some...

Entanglement is an important concept in quantum information, communication, and computing. We provide a geometrical analysis of entanglement separability for all the rank 2 mixed states: complete bipartite states partial multipartite states. For each state, we define its unique Bloch sphere, that spanned by eigenstates density matrix. characterize those spheres into exactly five classes separability, give examples class, prove are only classes.

A semiquantum key distribution (SQKD) protocol makes it possible for a quantum party and classical to generate secret shared key. However, many existing SQKD protocols are not experimentally feasible in secure way using current technology. An protocol, “classical Alice with controllable mirror” (the “Mirror protocol”), has recently been presented proved completely robust, but is more complicated than other protocols. Here we prove simpler variant of the Mirror “simplified protocol”) be...

The Quantum Key Distribution (QKD) protocol BB84 has been proven secure against several important types of attacks: the collective attacks and joint attacks. Here we analyze security a modified protocol, for which information is sent only in z basis while testing done both x bases, proof follows framework previous paper (Boyer, Gelles, Mor, 2009), but it avoids classical information-theoretical analysis that caused problems with composability. We show this as original requires more bits testing.

Quantum key distribution (QKD) protocols aim at allowing two parties to generate a secret shared key. While many QKD have been proven unconditionally secure in theory, practical security analyses of experimental implementations typically do not take into account all possible loopholes, and devices are still fully characterized for obtaining tight realistic rates. We present simple method computing rates any implementation discrete-variable (which can also apply measurement-device-independent...

Abstract We present a complete classification of the geometry mutually complementary sets entangled and separable states in three-dimensional Hilbert subspaces bipartite multipartite quantum systems. Our analysis begins by finding geometric structure pure product given subspace, which determines all possible mixed over same subspace. In systems, we characterise 14 qualitatively different shapes for set any subspace (5 classes also appear two-dimensional were found analysed Boyer et al. (Phys...

Continuous variable quantum key distribution (CVQKD) with discrete modulation combines advantages of CVQKD, such as the implementability using readily available technologies, distribution, easier error correction procedures. We consider a prepare-and-measure CVQKD protocol, where Alice chooses from set four coherent states and Bob performs heterodyne measurement, result which is discretised in both test rounds. provide security proof against attacks finite-size regime, compute achievable...

Semiquantum key distribution (SQKD) allows two parties (Alice and Bob) to create a shared secret key, even if one of these (say, Alice) is classical. However, most SQKD protocols suffer from severe practical security problems when implemented using photons. The recently developed "Mirror protocol" [Boyer, Katz, Liss, Mor, Phys. Rev. A 96, 062335 (2017)] an experimentally feasible protocol overcoming those drawbacks. Mirror was proven robust (namely, it secure against limited class attacks...

Quantum key distribution (QKD) protocols make it possible for two parties to generate a secret shared key. One of the most important QKD protocols, BB84, was suggested by Bennett and Brassard in 1984. Various proofs unconditional security BB84 have been suggested, but first were not composable. Here we improve proof given [Biham, Boyer, Boykin, Mor, Roychowdhury, J. Cryptology, 19(4):381-439, 2006] be composable match state-of-the-art results extend prove several variants protocol. Our its...

The counter-intuitive features of Quantum Mechanics make it possible to solve problems and perform tasks that are beyond the abilities classical computers communication devices. area quantum information processing studies how representing by states can help achieving such improvements.In this research, we use basic notions (mainly entanglement, Bloch sphere, geometrical distances between states) for analyzing relations each other cryptographic protocols.Entanglement is an important feature...

We present a complete classification of the geometry mutually complementary sets entangled and separable states in three-dimensional Hilbert subspaces bipartite multipartite quantum systems. Our analysis begins by finding geometric structure pure product given subspace, which determines all possible mixed over same subspace. In systems, we characterise 14 qualitatively different shapes for set any subspace (5 classes also appear two-dimensional were found analysed Boyer, Liss Mor [Phys. Rev....

Abstract A Bloch sphere is the geometrical representation of an arbitrary two-dimensional Hilbert space. Possible classes entanglement and separability for pure mixed states on were suggested by [Boyer et al 2017 PRA 95 032 308]. Here we construct a space spanned one ground Kitaev’s toric code model its closest product states. We prove that this contains only separable state, thus belonging to fourth class said paper. furthermore study topological order surface conclude that, according...

The counter-intuitive features of quantum mechanics make it possible to solve problems and perform tasks that are beyond the abilities non-quantum (classical) computers communication devices. field information processing studies how we can achieve such improvements by representing as states.One early achievements is development key distribution (QKD). QKD protocols allow two participants (Alice Bob) classically-impossible task generating a secret shared even if their adversary...

Quantum key distribution (QKD) protocols aim at allowing two parties to generate a secret shared key. While many QKD have been proven unconditionally secure in theory, practical security analyses of experimental implementations typically do not take into account all possible loopholes, and devices are still fully characterized for obtaining tight realistic rates. We present simple method computing rates any implementation discrete-variable (which can also apply measurement-device-independent...

Finding the ground state energy of Heisenberg Hamiltonian is an important problem in field condensed matter physics. In some configurations, such as antiferromagnetic translationally-invariant case on 2D square lattice, its exact still unknown. We show that finding model cannot be NP-Hard unless P=NP. prove this result using a reduction to sparse set and certain theorems from computational complexity theory. The hints at potential tractability encourages further research towards positive...