1,805 research outputs found
Black Hole Entropy and Entropy of Entanglement
We compare the one-loop corrections to the entropy of a black hole, from
quantum fields of spin zero, one-half, and one, to the entropy of entanglement
of the fields. For fields of spin zero and one-half the black hole entropy is
identical to the entropy of entanglement. For spin one the two entropies differ
by a contact interaction with the horizon which appears in the black hole
entropy but not in the entropy of entanglement. The contact interaction can be
expressed as a path integral over particle paths which begin and end on the
horizon; it is the field theory limit of the interaction proposed by Susskind
and Uglum which couples a closed string to an open string stranded on the
horizon.Comment: 22 pages, 2 figures, uses harvmac and epsf fixed three minor sign
errors, improved the writing in place
Entangling spins by measuring charge: a parity-gate toolbox
The parity gate emerged recently as a promising resource for performing
universal quantum computation with fermions using only linear interactions.
Here we analyse the parity gate (P-gate) from a theoretical point of view in
the context of quantum networks. We present several schemes for entanglement
generation with P-gates and show that native networks simplify considerably the
resources required for producing multi-qubit entanglement, like n-GHZ states.
Other applications include a Bell-state analyser and teleportation. We also
show that cluster state fusion can be performed deterministically with parity
measurements. We then extend this analysis to hybrid quantum networks
containing spin and mode qubits. Starting from an easy-to-prepare resource
(spin-mode entanglement of single electrons) we show how to produce a spin
n-GHZ state with linear elements (beam-splitters and local spin-flips) and
charge-parity detectors; this state can be used as a resource in a spin quantum
computer or as a precursor for constructing cluster states. Finally, we
construct a novel spin CZ-gate by using the mode degrees of freedom as
ancillae.Comment: updated to the published versio
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