448 research outputs found
Probing Positron Gravitation at HERA
An equality of particle and antiparticle gravitational interactions holds in
general relativity and is supported by indirect observations. Here I develop a
method based on high energy Compton scattering to measure the gravitational
interaction of accelerated charged particles. Within that formalism the Compton
spectra measured at HERA rule out the positron's anti-gravity and hint for a
positron's 1.3(0.2)\% weaker coupling to the gravitational field relative to an
electron
Accelerator experiments contradicting general relativity
The deflection of gamma-rays in Earth's gravitational field is tested in
laser Compton scattering at high energy accelerators. Within a formalism
connecting the bending angle to the photon's momentum it follows that detected
gamma-ray spectra are inconsistent with a deflection magnitude of 2.78 nrad,
predicted by Einstein's gravity theory. Moreover, preliminary results for 13-28
GeV photons from two different laboratories show opposite - away from the Earth
- deflection, amounting to 33.8-0.8 prad. I conclude that general relativity,
which describes gravity at low energies precisely, break down at high energies.Comment: text correction on page 2: "order of " replaced by "order of
Probing Positron Gravitation at HERA
An equality of particle and antiparticle gravitational interactions holds in
general relativity and is supported by indirect observations. Here I develop a
method based on high energy Compton scattering to measure the gravitational
interaction of accelerated charged particles. Within that formalism the Compton
spectra measured at HERA rule out the positron's anti-gravity and hint for a
positron's 1.3(0.2)\% weaker coupling to the gravitational field relative to an
electron
Reply to "Comment on Testing Planck-Scale Gravity with Accelerators"
Results of a 2012 PRL Letter have recently been questioned by T. Kalaydzhyan
in arXiv:1604.04486. Here we confirm our original results and conclusions by
addressing all concerns raised in the Comment
Sharpening the Second Law of Thermodynamics with the Quantum Bayes' Theorem
We prove a generalization of the classic Groenewold-Lindblad entropy
inequality, combining decoherence and the quantum Bayes theorem into a simple
unified picture where decoherence increases entropy while observation decreases
it. This provides a rigorous quantum-mechanical version of the second law of
thermodynamics, governing how the entropy of a system (the entropy of its
density matrix, partial-traced over the environment and conditioned on what is
known) evolves under general decoherence and observation. The powerful tool of
spectral majorization enables both simple alternative proofs of the classic
Lindblad and Holevo inequalities without using strong subadditivity, and also
novel inequalities for decoherence and observation that hold not only for von
Neumann entropy, but also for arbitrary concave entropies.Comment: Replaced to match accepted PRE version. Significantly expanded,
including proofs of which entropy theorems hold for which types of
interactions (probing, purity-preserving POVMs, etc). 7 pages, 2 fig
Are entangled particles connected by wormholes? Support for the ER=EPR conjecture from entropy inequalities
If spacetime is built out of quantum bits, does the shape of space depend on
how the bits are entangled? The ER=EPR conjecture relates the entanglement
entropy of a collection of black holes to the cross sectional area of
Einstein-Rosen (ER) bridges (or wormholes) connecting them. We show that the
geometrical entropy of classical ER bridges satisfies the subadditivity,
triangle, strong subadditivity, and CLW inequalities. These are nontrivial
properties of entanglement entropy, so this is evidence for ER=EPR. We further
show that the entanglement entropy associated to classical ER bridges has
nonpositive interaction information. This is not a property of entanglement
entropy, in general. For example, the entangled four qubit pure state
|GHZ_4>=(|0000>+|1111>)/\sqrt{2} has positive interaction information, so this
state cannot be described by a classical ER bridge. Large black holes with
massive amounts of entanglement between them can fail to have a classical ER
bridge if they are built out of |GHZ_4> states. States with nonpositive
interaction information are called monogamous. We conclude that classical ER
bridges require monogamous EPR correlations.Comment: 11 pages, 4 figure
A Quantum Multiparty Packing Lemma and the Relay Channel
Optimally encoding classical information in a quantum system is one of the
oldest and most fundamental challenges of quantum information theory. Holevo's
bound places a hard upper limit on such encodings, while the
Holevo-Schumacher-Westmoreland (HSW) theorem addresses the question of how many
classical messages can be "packed" into a given quantum system. In this
article, we use Sen's recent quantum joint typicality results to prove a
one-shot multiparty quantum packing lemma generalizing the HSW theorem. The
lemma is designed to be easily applicable in many network communication
scenarios. As an illustration, we use it to straightforwardly obtain quantum
generalizations of well-known classical coding schemes for the relay channel:
multihop, coherent multihop, decode-forward, and partial decode-forward. We
provide both finite blocklength and asymptotic results, the latter matching
existing classical formulas. Given the key role of the classical packing lemma
in network information theory, our packing lemma should help open the field to
direct quantum generalization.Comment: 20 page
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