Wyszukiwarka
prof. dr hab. Paweł Horodecki
Zatrudnienie
- Profesor w Instytut Fizyki i Informatyki Stosowanej
Publikacje
Filtry
wszystkich: 119
Katalog Publikacji
Rok 2014
-
Sensitivity of entanglement decay of quantum-dot spin qubits to the external magnetic field
PublikacjaWe study the decay of entanglement of quantum-dot electron-spin qubits under hyperfine-interaction-mediated decoherence.We show that two-qubit entanglement of a single entangled initial state may exhibit decay characteristic of two disentanglement regimes in a single sample, when the externalmagnetic field is changed. The transition is manifested by the suppression of time-dependent entanglement oscillations which are superimposed...
-
Strong Monogamies of No-Signaling Violations for Bipartite Correlation Bell Inequalities
PublikacjaThe phenomenon of monogamy of Bell inequality violations is interesting both from the fundamental perspective as well as in cryptographic applications such as the extraction of randomness and secret bits. In this article, we derive new and stronger monogamy relations for violations of Bell inequalities in general no-signaling theories. These relations are applicable to the class of binary output correlation inequalities known as...
-
The decay of quantum correlations between quantum dot spin qubits and the characteristics of its magnetic-field dependence
PublikacjaWe address the question of the role of quantum correlations beyond entanglement in the context of quantum magnetometry. We study the evolution of the rescaled variant of the geometric quantum discord of two electron-spin qubits interacting with an environment of nuclear spins via the hyperfine interaction. We have found that quantum correlations display a strong magnetic-field sensitivity which can be utilized for decoherence-driven...
Rok 2013
-
Separability in terms of a single entanglement witness
PublikacjaThe separability problem is formulated in terms of a characterization of a single entanglement witness. More specifically, we show that any (in general multipartite) state rho is separable if and only if a specially constructed entanglement witness W-rho is weakly optimal, i.e., its expectation value vanishes on at least one product vector. Interestingly, the witness can always be chosen to be decomposable. Our result changes the...
Rok 2016
-
Sharp transitions in low-number quantum dots Bayesian magnetometry
PublikacjaWe consider Bayesian estimate of static magnetic field, characterized by a prior Gaussian probability distribution, in systems of a few electron quantum dot spins interacting with infinite temperature spin environment via hyperfine interaction. Sudden transitions among optimal states and measurements are observed. Usefulness of measuring occupation levels is shown for all times of the evolution, together with the role of entanglement...
Rok 2009
-
Squashed entanglement for multipartite states and entanglement measures based on the mixed convex roof
PublikacjaNew measures of multipartite entanglement are constructedbased on two definitions of multipartite information anddifferent methods of optimizing over extensions of the states. Oneis a generalization of the squashed entanglement where one takesthe mutual information of parties conditioned on the state's extensionand takes the infimum over such extensions. Additivity ofthe multipartite squashed entanglement is proved for both versionsof...
-
W-like bound entangled states and secure key distillation
PublikacjaWe construct multipartite entangled states with underlying W-type structuresatisfying positive partial transpose (PPT) condition under any (N −1)|1 partition. Then we showhow to distill a N-partite secure key from the states using two different methods: direct applicationof local filtering and novel random key distillation scheme in which we adopt the idea from recentresults on entanglement distillation. Open problems and possible...
Rok 2018
-
Steering is an essential feature of non-locality in quantum theory
PublikacjaA physical theory is called non-local when observers can produce instantaneous effects over distant systems. Non-local theories rely on two fundamental effects: local uncertainty relations and steering of physical states at a distance. In quantum mechanics, the former one dominates the other in a well-known class of non-local games known as XOR games. In particular, optimal quantum strategies for XOR games are completely determined...
-
System information propagation for composite structures
PublikacjaWe study in details decoherence process of a spin register, coupled to a spin environment. We use recently developed methods of information transfer study in open quantum systems to analyze information flow between the register and its environment. We show that there are regimes when not only the register decoheres effectively to a classical bit string, but this bit string is redundantly encoded in the environment, making it available...
Rok 2010
-
Sudden death of effective entanglement
PublikacjaSudden death of entanglement is a well-known effect resulting from the finite volume of separable states. We study the case when the observer has a limited measurement capability and analyze the effective entanglement (i.e., entanglement minimized over the output data). We show that in the well-defined system of two quantum dots monitored by single-electron transistors, one may observe a sudden death of effective entanglement when...
Rok 2017
-
Superadditivity of two quantum information resources
PublikacjaEntanglement is one of the most puzzling features of quantum theory and a principal resource for quantum information processing. It is well known that in classical information theory, the addition of two classical information resources will not lead to any extra advantages. On the contrary, in quantum information, a spectacular phenomenon of the superadditivity of two quantum information resources emerges. It shows that quantum...
-
Zero-knowledge convincing protocol on quantum bit is impossible
PublikacjaIt is one of fundamental features of quantum formalism that o n one hand it provides a new infor- mation processing resources and on the other hand puts funda mental constraints on the processing of quantum information implying “no-go” theorems for cloni ng [1–3], bit commitment [4, 5] and deleting [6] in quantum theory. Here we ask about possibilit y of “zero knowledge” scenario which, for its simplicity, can be considered as...
Rok 2004
-
TelePOVM - A generalized quantum teleportation scheme.
PublikacjaPokazano, że kwantowa teleportacja jest specjalnym przypadkiem uogólnionej nielokalności EPR.
-
Termodynamics of quantum information systems - Hamiltonian description.
PublikacjaPrzy użyciu podejścia hamiltonowskiego wyprowadzono wzór na pracę dla układów kwantowych zanurzonych w ciepłym otoczeniu.
-
The ab initio calculations of single nitrogen-vacancy defect center in diamond.
PublikacjaW artykule zaprezentowano rezultaty kwantowomechanicznych obliczeń ''ab initio'' struktury elektronowej defektu azot-wakans w diamencie. Do obliczeń wykorzystano model złożony z 63 atomów. Otrzymane wyniki zostały porównane z wcześniejszymi pracami teoretycznymi i doświadczalnymi.
Rok 2002
-
Thermodynamical approach to quantifying quantum correlations
PublikacjaWe consider the amount of work which can be extracted from a heat bath using a bipartite state ρ shared by two parties. In general it is less then the amount of work extractable when one party is in possession of the entire state. We derive bounds for this “work deficit” and calculate it explicitly for a number of different cases. In particuar, for pure states the work deficit is exactly equal to the distillable entanglement of...
Rok 2008
-
Unconditional privacy over channels which cannot convey quantum information
PublikacjaQuantum cryptography enables one to verify that the state of the quantum system has not been tampered with and thus one can obtain privacy regardless of the power of the eavesdropper. All previous protocols relied on the ability to faithfully send quantum states or equivalently to share pure entanglement. Here we show this need not be the case-one can obtain verifiable privacy even through some channels which cannot be used to...
-
Universal observable detecting all two-qubit entanglement and determinant-based separability tests
PublikacjaW pracy zbadano możliwość konstrukcji uniwersalnej obserwabli, którejwartość średnia na pewnej ilości kopii danego stanu kwantowegorozstrzygałaby jednoznacznie i niezależnie od badanego stany czy jest on splątany. Pokazano, że w przypadku dwukubitowych stanów kwantowych konstrukcja takiej obserwabli jest możliwa oraz ilość kopii potrzebna do zmierzenia jej wartości średniej jest równa cztery. Ponadto, zbadano czy wartość średnia...
Rok 2007
-
Unifying classical and quantum key distillation
PublikacjaPrzypuśćmy, że dwie oddalone od siebie osoby, Alicja i Bob, oraz osoba z nimi niewspółpracująca, Ewa, mają dostęp do systemów kwantowych przygotowanych w stanie rho_ABE. Ponadto Alicja i Bob mogą używać lokalnych operacji i uwiarygodnionej komunikacji publicznej. Celem Alicji i Boba jest ustanowienie klucza, który nie będzie znany Ewie. Nasze badania inicjują podejście do wspomnianego zagadnienia oparte na unifikacji dwóch standardowych...
wyświetlono 4045 razy