9,514 research outputs found
Anisotropic pair-superfluidity of trapped two-component Bose gases
We theoretically investigate the pair-superfluid phase of two-component
ultracold gases with negative inter-species interactions in an optical lattice.
We establish the phase diagram for filling at zero and finite
temperature, by applying Bosonic Dynamical Mean-Field Theory, and confirm the
stability of pair-superfluidity for asymmetric hopping of the two species.
While the pair superfluid is found to be robust in the presence of a harmonic
trap, we observe that it is destroyed already by a small population imbalance
of the two species.Comment: 7 pages, 11 figure
The evolution of misbelief
From an evolutionary standpoint, a default presumption is that true beliefs are adaptive and misbeliefs maladaptive. But if humans are biologically engineered to appraise the world accurately and to form true beliefs, how are we to explain the routine exceptions to this rule? How can we account for mistaken beliefs, bizarre delusions, and instances of self-deception? We explore this question in some detail. We begin by articulating a distinction between two general types of misbelief: those resulting from a breakdown in the normal functioning of the belief formation system (e.g., delusions) and those arising in the normal course of that system's operations (e.g., beliefs based on incomplete or inaccurate information). The former are instances of biological dysfunction or pathology, reflecting "culpable” limitations of evolutionary design. Although the latter category includes undesirable (but tolerable) by-products of "forgivably” limited design, our quarry is a contentious subclass of this category: misbeliefs best conceived as design features. Such misbeliefs, unlike occasional lucky falsehoods, would have been systematically adaptive in the evolutionary past. Such misbeliefs, furthermore, would not be reducible to judicious - but doxastically1 noncommittal - action policies. Finally, such misbeliefs would have been adaptive in themselves, constituting more than mere by-products of adaptively biased misbelief-producing systems. We explore a range of potential candidates for evolved misbelief, and conclude that, of those surveyed, only positive illusions meet our criteri
Pairing, crystallization and string correlations of mass-imbalanced atomic mixtures in one-dimensional optical lattices
We numerically determine the very rich phase diagram of mass-imbalanced
binary mixtures of hardcore bosons (or equivalently -- fermions, or
hardcore-Bose/Fermi mixtures) loaded in one-dimensional optical lattices.
Focusing on commensurate fillings away from half filling, we find a strong
asymmetry between attractive and repulsive interactions. Attraction is found to
always lead to pairing, associated with a spin gap, and to pair crystallization
for very strong mass imbalance. In the repulsive case the two atomic components
remain instead fully gapless over a large parameter range; only a very strong
mass imbalance leads to the opening of a spin gap. The spin-gap phase is the
precursor of a crystalline phase occurring for an even stronger mass imbalance.
The fundamental asymmetry of the phase diagram is at odds with recent
theoretical predictions, and can be tested directly via time-of-flight
experiments on trapped cold atoms.Comment: 4 pages, 4 figures + Supplementary Materia
Random access quantum information processors
Qubit connectivity is an important property of a quantum processor, with an
ideal processor having random access -- the ability of arbitrary qubit pairs to
interact directly. Here, we implement a random access superconducting quantum
information processor, demonstrating universal operations on a nine-bit quantum
memory, with a single transmon serving as the central processor. The quantum
memory uses the eigenmodes of a linear array of coupled superconducting
resonators. The memory bits are superpositions of vacuum and single-photon
states, controlled by a single superconducting transmon coupled to the edge of
the array. We selectively stimulate single-photon vacuum Rabi oscillations
between the transmon and individual eigenmodes through parametric flux
modulation of the transmon frequency, producing sidebands resonant with the
modes. Utilizing these oscillations for state transfer, we perform a universal
set of single- and two-qubit gates between arbitrary pairs of modes, using only
the charge and flux bias of the transmon. Further, we prepare multimode
entangled Bell and GHZ states of arbitrary modes. The fast and flexible
control, achieved with efficient use of cryogenic resources and control
electronics, in a scalable architecture compatible with state-of-the-art
quantum memories is promising for quantum computation and simulation.Comment: 7 pages, 5 figures, supplementary information ancillary file, 21
page
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Beagle to the Moon: nn experiment package to measure polar ice and volatiles in permanently shadowed areas or beneath the lunar surface
The Beagle Science Package is a flight qualified set of instruments which should be deployed to the lunar surface to answer the questions about water and volatiles present in permanently shadowed regions and/or beneath the surface
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