382 research outputs found
On Renormalons and Landau Poles in Gauge Field Theories
It is shown that the commonly accepted relationship between the Landau
singularity in the running coupling constant of QED or QCD and the renormalon
singularities in the Borel sums of perturbation theory expansions is only a
particular feature of the restriction of the perturbative --function to
the one loop level.Comment: 11 pages, latex. One comment and one reference adde
L'homologie de Novikov des entrelacs de Waldhausen
A graph multilink is a link with multiplicities in a homology 3-sphere whose
exterior is a graph manifold. In this Note, we compute the Novikov homology of
graph multilinks. As a corollary, we give a majoration for the number of
Novikov modules on a given graph link.Comment: 4 pages, 2 figure
Infrared Renormalons and Finite Volume
We analyze the perturbative expansion of a condensate in the O(N) non-linear
sigma model for large N on a two dimensional finite lattice. On an infinite
volume this expansion is affected by an infrared renormalon. We extrapolate
this analysis to the case of the gluon condensate of Yang-Mills theory and
argue that infrared renormalons can be detected by performing perturbative
studies even on relatively small lattices.Comment: LaTeX file, 6 figures in postscrip
Entangled resource for interfacing single- and dual-rail optical qubits
Today's most widely used method of encoding quantum information in optical
qubits is the dual-rail basis, often carried out through the polarisation of a
single photon. On the other hand, many stationary carriers of quantum
information - such as atoms - couple to light via the single-rail encoding in
which the qubit is encoded in the number of photons. As such, interconversion
between the two encodings is paramount in order to achieve cohesive quantum
networks. In this paper, we demonstrate this by generating an entangled
resource between the two encodings and using it to teleport a dual-rail qubit
onto its single-rail counterpart. This work completes the set of tools
necessary for the interconversion between the three primary encodings of the
qubit in the optical field: single-rail, dual-rail and continuous-variable.Comment: Published in Quantu
An Introduction to the Inverse Quantum Bound State Problem in One Dimension
A technique to reconstruct one-dimensional, reflectionless potentials and the
associated quantum wave functions starting from a finite number of known energy
spectra is discussed. The method is demonstrated using spectra that scale like
the lowest energy states of standard problems encountered in the undergraduate
curriculum such as: the infinite square well, the simple harmonic oscillator,
and the one-dimensional hydrogen atom.Comment: 10 pages, 10 figures, Submitted to Am. J. Phys. August 201
Exploring More-Coherent Quantum Annealing
In the quest to reboot computing, quantum annealing (QA) is an interesting
candidate for a new capability. While it has not demonstrated an advantage over
classical computing on a real-world application, many important regions of the
QA design space have yet to be explored. In IARPA's Quantum Enhanced
Optimization (QEO) program, we have opened some new lines of inquiry to get to
the heart of QA, and are designing testbed superconducting circuits and
conducting key experiments. In this paper, we discuss recent experimental
progress related to one of the key design dimensions: qubit coherence. Using
MIT Lincoln Laboratory's qubit fabrication process and extending recent
progress in flux qubits, we are implementing and measuring QA-capable flux
qubits. Achieving high coherence in a QA context presents significant new
engineering challenges. We report on techniques and preliminary measurement
results addressing two of the challenges: crosstalk calibration and qubit
readout. This groundwork enables exploration of other promising features and
provides a path to understanding the physics and the viability of quantum
annealing as a computing resource.Comment: 7 pages, 3 figures. Accepted by the 2018 IEEE International
Conference on Rebooting Computing (ICRC
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