@article {1326,
title = {Quantum Interactions with Closed Timelike Curves and Superluminal Signaling
},
journal = {Physical Review A},
volume = {89},
year = {2014},
month = {2014/2/12},
abstract = { There is now a significant body of results on quantum interactions with
closed timelike curves (CTCs) in the quantum information literature, for both
the Deutsch model of CTC interactions (D-CTCs) and the projective model
(P-CTCs). As a consequence, there is a prima facie argument exploiting
entanglement that CTC interactions would enable superluminal and, indeed,
effectively instantaneous signaling. In cases of spacelike separation between
the sender of a signal and the receiver, whether a receiver measures the local
part of an entangled state or a disentangled state to access the signal can
depend on the reference frame. We propose a consistency condition that gives
priority to either an entangled perspective or a disentangled perspective in
spacelike separated scenarios. For D-CTC interactions, the consistency
condition gives priority to frames of reference in which the state is
disentangled, while for P-CTC interactions the condition selects the entangled
state. Using the consistency condition, we show that there is a procedure that
allows Alice to signal to Bob in the past via relayed superluminal
communications between spacelike separated Alice and Clio, and spacelike
separated Clio and Bob. This opens the door to time travel paradoxes in the
classical domain. Ralph (arXiv:1107.4675) first pointed this out for P-CTCs,
but we show that Ralph{\textquoteright}s procedure for a {\textquoteright}radio to the past{\textquoteright} is flawed. Since
both D-CTCs and P-CTCs allow classical information to be sent around a
spacetime loop, it follows from a result by Aaronson and Watrous
(Proc.Roy.Soc.A, 465:631-647 (2009)) for CTC-enhanced classical computation
that a quantum computer with access to P-CTCs would have the power of PSPACE,
equivalent to a D-CTC-enhanced quantum computer.
},
doi = {10.1103/PhysRevA.89.022311},
url = {http://arxiv.org/abs/1309.4751v4},
author = {Jeffrey Bub and Allen Stairs}
}
@article {1325,
title = {Contextuality in Quantum Mechanics: Testing the Klyachko Inequality},
year = {2010},
month = {2010/06/02},
abstract = { The Klyachko inequality is an inequality for the probabiities of the values
of five observables of a spin-1 particle, which is satisfied by any
noncontextual assignment of values to this set of observables, but is violated
by the probabilities defined by a certain quantum state. We describe an
experiment between two entangled spin-1 particles to test contextuality via a
related inequality. We point out that a test of contextuality by measurements
on a single particle to confirm the Klyachko inequality requires an assumption
of non-disturbance by the measuring instrument, which is avoided in the
two-particle experiment.
},
url = {http://arxiv.org/abs/1006.0500v2},
author = {Jeffrey Bub and Allen Stairs}
}
@article {1324,
title = {Contextuality and nonlocality in {\textquoteright}no signaling{\textquoteright} theories},
journal = {Foundations of Physics},
volume = {39},
year = {2009},
month = {2009/4/21},
pages = {690 - 711},
abstract = { We define a family of {\textquoteright}no signaling{\textquoteright} bipartite boxes with arbitrary inputs
and binary outputs, and with a range of marginal probabilities. The defining
correlations are motivated by the Klyachko version of the Kochen-Specker
theorem, so we call these boxes Kochen-Specker-Klyachko boxes or, briefly,
KS-boxes. The marginals cover a variety of cases, from those that can be
simulated classically to the superquantum correlations that saturate the
Clauser-Horne-Shimony-Holt inequality, when the KS-box is a generalized PR-box
(hence a vertex of the {\textquoteleft}no signaling{\textquoteright} polytope). We show that for certain
marginal probabilities a KS-box is classical with respect to nonlocality as
measured by the Clauser-Horne-Shimony-Holt correlation, i.e., no better than
shared randomness as a resource in simulating a PR-box, even though such
KS-boxes cannot be perfectly simulated by classical or quantum resources for
all inputs. We comment on the significance of these results for contextuality
and nonlocality in {\textquoteright}no signaling{\textquoteright} theories.
},
doi = {10.1007/s10701-009-9307-8},
url = {http://arxiv.org/abs/0903.1462v2},
author = {Jeffrey Bub and Allen Stairs}
}
@article {1322,
title = {Conditionalizing and commutativity: a note on Malley},
year = {2005},
month = {2005/06/19},
abstract = { This paper has been withdrawn.
},
url = {http://arxiv.org/abs/quant-ph/0506159v2},
author = {Allen Stairs and Jeffrey Bub}
}