6,746 research outputs found
Multi-photon entanglement and interferometry
Multi-photon interference reveals strictly non-classical phenomena. Its
applications range from fundamental tests of quantum mechanics to photonic
quantum information processing, where a significant fraction of key experiments
achieved so far comes from multi-photon state manipulation. We review the
progress, both theoretical and experimental, of this rapidly advancing
research. The emphasis is given to the creation of photonic entanglement of
various forms, tests of the completeness of quantum mechanics (in particular,
violations of local realism), quantum information protocols for quantum
communication (e.g., quantum teleportation, entanglement purification and
quantum repeater), and quantum computation with linear optics. We shall limit
the scope of our review to "few photon" phenomena involving measurements of
discrete observables.Comment: 71 pages, 38 figures; updated version accepted by Rev. Mod. Phy
On the group theoretic structure of a class of quantum dialogue protocols
Intrinsic symmetry of the existing protocols of quantum dialogue are
explored. It is shown that if we have a set of mutually orthogonal -qubit
states {\normalsize
and a set of
() unitary operators
and
forms a group under multiplication then it
would be sufficient to construct a quantum dialogue protocol using this set of
quantum states and this group of unitary operators}. The sufficiency condition
is used to provide a generalized protocol of quantum dialogue. Further the
basic concepts of group theory and quantum mechanics are used here to
systematically generate several examples of possible groups of unitary
operators that may be used for implementation of quantum dialogue. A large
number of examples of quantum states that may be used to implement the
generalized quantum dialogue protocol using these groups of unitary operators
are also obtained. For example, it is shown that GHZ state, GHZ-like state, W
state, 4 and 5 qubit Cluster states, Omega state, Brown state, state
and state can be used for implementation of quantum dialogue protocol.
The security and efficiency of the proposed protocol is appropriately analyzed.
It is also shown that if a group of unitary operators and a set of mutually
orthogonal states are found to be suitable for quantum dialogue then they can
be used to provide solutions of socialist millionaire problem.Comment: 15 page
Multiparty Quantum Communication Using Multiqubit Entanglement and Teleportation
We propose a 2N qubit entangled channel that can be used to teleport N qubits in a network to a single receiver. We describe the structure of this channel and explicitly demonstrate how the protocol works. The channel can be used to implement a scheme in which all parties have to participate in order for the teleportation to be successful. This can be advantageous in various scenarios and we discuss the potential application of this protocol to voting
A domain-specific language and matrix-free stencil code for investigating electronic properties of Dirac and topological materials
We introduce PVSC-DTM (Parallel Vectorized Stencil Code for Dirac and
Topological Materials), a library and code generator based on a domain-specific
language tailored to implement the specific stencil-like algorithms that can
describe Dirac and topological materials such as graphene and topological
insulators in a matrix-free way. The generated hybrid-parallel (MPI+OpenMP)
code is fully vectorized using Single Instruction Multiple Data (SIMD)
extensions. It is significantly faster than matrix-based approaches on the node
level and performs in accordance with the roofline model. We demonstrate the
chip-level performance and distributed-memory scalability of basic building
blocks such as sparse matrix-(multiple-) vector multiplication on modern
multicore CPUs. As an application example, we use the PVSC-DTM scheme to (i)
explore the scattering of a Dirac wave on an array of gate-defined quantum
dots, to (ii) calculate a bunch of interior eigenvalues for strong topological
insulators, and to (iii) discuss the photoemission spectra of a disordered Weyl
semimetal.Comment: 16 pages, 2 tables, 11 figure
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