1,147 research outputs found
Generalized multi-photon quantum interference
Non-classical interference of photons lies at the heart of optical quantum
information processing. This effect is exploited in universal quantum gates as
well as in purpose-built quantum computers that solve the BosonSampling
problem. Although non-classical interference is often associated with perfectly
indistinguishable photons this only represents the degenerate case, hard to
achieve under realistic experimental conditions. Here we exploit tunable
distinguishability to reveal the full spectrum of multi-photon non-classical
interference. This we investigate in theory and experiment by controlling the
delay times of three photons injected into an integrated interferometric
network. We derive the entire coincidence landscape and identify transition
matrix immanants as ideally suited functions to describe the generalized case
of input photons with arbitrary distinguishability. We introduce a compact
description by utilizing a natural basis which decouples the input state from
the interferometric network, thereby providing a useful tool for even larger
photon numbers
Many-Electron Integrals over Gaussian Basis Functions. I. Recurrence Relations for Three-Electron Integrals
Explicitly correlated F12 methods are becoming the first choice for high-accuracy molecular orbital calculations and can often achieve chemical accuracy with relatively small Gaussian basis sets. In most calculations, the many three- and four-electron integrals that formally appear in the theory are avoided through judicious use of resolutions of the identity (RI). However, for the intrinsic accuracy of the F12 wave function to not be jeopardized, the associated RI auxiliary basis set must be large. Here, inspired by the Head-Gordon-Pople and PRISM algorithms for two-electron integrals, we present an algorithm to directly compute three-electron integrals over Gaussian basis functions and a very general class of three-electron operators without invoking RI approximations. A general methodology to derive vertical, transfer, and horizontal recurrence relations is also presented
The harmonic hyperspherical basis for identical particles without permutational symmetry
The hyperspherical harmonic basis is used to describe bound states in an
--body system. The approach presented here is based on the representation of
the potential energy in terms of hyperspherical harmonic functions. Using this
representation, the matrix elements between the basis elements are simple, and
the potential energy is presented in a compact form, well suited for numerical
implementation. The basis is neither symmetrized nor antisymmetrized, as
required in the case of identical particles; however, after the diagonalization
of the Hamiltonian matrix, the eigenvectors reflect the symmetries present in
it, and the identification of the physical states is possible, as it will be
shown in specific cases. We have in mind applications to atomic, molecular, and
nuclear few-body systems in which symmetry breaking terms are present in the
Hamiltonian; their inclusion is straightforward in the present method. As an
example we solve the case of three and four particles interacting through a
short-range central interaction and Coulomb potential
Quantum Discord and Quantum Computing - An Appraisal
We discuss models of computing that are beyond classical. The primary
motivation is to unearth the cause of nonclassical advantages in computation.
Completeness results from computational complexity theory lead to the
identification of very disparate problems, and offer a kaleidoscopic view into
the realm of quantum enhancements in computation. Emphasis is placed on the
`power of one qubit' model, and the boundary between quantum and classical
correlations as delineated by quantum discord. A recent result by Eastin on the
role of this boundary in the efficient classical simulation of quantum
computation is discussed. Perceived drawbacks in the interpretation of quantum
discord as a relevant certificate of quantum enhancements are addressed.Comment: To be published in the Special Issue of the International Journal of
Quantum Information on "Quantum Correlations: entanglement and beyond." 11
pages, 4 figure
Multipartite maximally entangled states in symmetric scenarios
We consider the class of (N+1)-partite states suitable for protocols where
there is a powerful party, the authority, and the other N parties play the same
role, namely the state of their system live in the symmetric Hilbert space. We
show that, within this scenario, there is a "maximally entangled state" that
can be transform by a LOCC protocol into any other state. In addition, we show
how to make the protocol efficiently including the construction of the state
and discuss security issues for possible applications to cryptographic
protocols. As an immediate consequence we recover a sequential protocol that
implements the one to N symmetric cloning.Comment: 6 pages, 4 figure
in a chiral constituent quark model and its interpolating fields
The recently discovered pentaquark is described within the chiral
constituent quark model. Within this picture the flavor-spin interaction
between valence quarks inverts the and levels of the
four-quark subsystem and consequently the lowest-lying pentaquark is a positive
parity, I=0, J=1/2 state of the flavor antidecuplet, similar to the soliton
model prediction. Contrary to the soliton model, however, the quark picture
predicts its spin-orbit partner with . Different interpolating fields
intended for lattice calculations of are constructed, which have a
maximal overlap with this baryon if it is indeed a quark excitation in the 5Q
system.Comment: 9 p
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