1,052 research outputs found
On the capacities of bipartite Hamiltonians and unitary gates
We consider interactions as bidirectional channels. We investigate the
capacities for interaction Hamiltonians and nonlocal unitary gates to generate
entanglement and transmit classical information. We give analytic expressions
for the entanglement generating capacity and entanglement-assisted one-way
classical communication capacity of interactions, and show that these
quantities are additive, so that the asymptotic capacities equal the
corresponding 1-shot capacities. We give general bounds on other capacities,
discuss some examples, and conclude with some open questions.Comment: V3: extensively rewritten. V4: a mistaken reference to a conjecture
by Kraus and Cirac [quant-ph/0011050] removed and a mistake in the order of
authors in Ref. [53] correcte
The linearization of the Kodama state
We study the question of whether the linearization of the Kodama state around
classical deSitter spacetime is normalizable in the inner product of the theory
of linearized gravitons on deSitter spacetime. We find the answer is no in the
Lorentzian theory. However, in the Euclidean theory the corresponding
linearized Kodama state is delta-functional normalizable. We discuss whether
this result invalidates the conjecture that the full Kodama state is a good
physical state for quantum gravity with positive cosmological constant.Comment: 14 pages, statement on the corresponding Yang-Mills case correcte
Local cloning of Bell states and distillable entanglement
The necessary and sufficient amount of entanglement required for cloning of
orthogonal Bell states by local operation and classical communication is
derived, and using this result, we provide here some additional examples of
reversible, as well as irreversible states.Comment: 5 pages, two columns, Latex. Few typos have been corrected. An
explanation of the teleportation map (eqn. (3) in the manuscript) has been
provide
Relative Locality in -Poincar\'e
We show that the -Poincar\'e Hopf algebra can be interpreted in the
framework of curved momentum space leading to the relativity of locality
\cite{AFKS}. We study the geometric properties of the momentum space described
by -Poincar\'e, and derive the consequences for particles propagation
and energy-momentum conservation laws in interaction vertices, obtaining for
the first time a coherent and fully workable model of the deformed relativistic
kinematics implied by -Poincar\'e. We describe the action of boost
transformations on multi-particles systems, showing that in order to keep
covariant the composed momenta it is necessary to introduce a dependence of the
rapidity parameter on the particles momenta themselves. Finally, we show that
this particular form of the boost transformations keeps the validity of the
relativity principle, demonstrating the invariance of the equations of motion
under boost transformations.Comment: 24 pages, 4 figures, 1 table. v2 matches accepted CQG versio
Simulating quantum operations with mixed environments
We study the physical resources required to implement general quantum
operations, and provide new bounds on the minimum possible size which an
environment must be in order to perform certain quantum operations. We prove
that contrary to a previous conjecture, not all quantum operations on a
single-qubit can be implemented with a single-qubit environment, even if that
environment is initially prepared in a mixed state. We show that a mixed
single-qutrit environment is sufficient to implement a special class of
operations, the generalized depolarizing channels.Comment: 4 pages Revtex + 1 fig, pictures at
http://stout.physics.ucla.edu/~smolin/tetrahedron .Several small correction
Reconstructing Quantum Geometry from Quantum Information: Spin Networks as Harmonic Oscillators
Loop Quantum Gravity defines the quantum states of space geometry as spin
networks and describes their evolution in time. We reformulate spin networks in
terms of harmonic oscillators and show how the holographic degrees of freedom
of the theory are described as matrix models. This allow us to make a link with
non-commutative geometry and to look at the issue of the semi-classical limit
of LQG from a new perspective. This work is thought as part of a bigger project
of describing quantum geometry in quantum information terms.Comment: 16 pages, revtex, 3 figure
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