10,439 research outputs found
Parting layers, ash trays and Ramesside glassmaking: an experimental study
A series of glassmaking and glass colouring
replication experiments was undertaken in order to
test some of the current hypotheses concerning Late
Bronze Age glass production at Qantir-Piramesses.
These were based on the model of glassmaking
developed in this volume, and aimed in particular to
test the behaviour of the parting layer and the local
ceramic under the proposed chemical and thermal
conditions. Modern ash trays made out of Egyptian
Nile silt clay were used as proxies for LBA reaction
vessels and crucibles, and both raw glass and
coloured glass ingots were produced in them. This
experimental study, based on detailed observation
and technical studies of archaeological samples from
Qantir-Piramesses, not only provides material
readily comparable to the archaeological finds, but
brings to the forefront practical issues concerning the
nature of the parting layer, its application, the
melting procedures, the re-use of crucibles, and
indirect evidence of primary production, such as the
impact of sodium chloride, a major component of
plant ashes, on the ceramic. Although this string of
experiments does not fully replicate LBA
glassmaking technology, much information was
obtained and further areas of ambiguity identified
Randomized Benchmarking as Convolution: Fourier Analysis of Gate Dependent Errors
We provide an alternative proof of Wallman's [Quantum 2, 47 (2018)] and
Proctor's [Phys. Rev. Lett. 119, 130502 (2017)] bounds on the effect of
gate-dependent noise on randomized benchmarking (RB). Our primary insight is
that a RB sequence is a convolution amenable to Fourier space analysis, and we
adopt the mathematical framework of Fourier transforms of matrix-valued
functions on groups established in recent work from Gowers and Hatami [Sbornik:
Mathematics 208, 1784 (2017)]. We show explicitly that as long as our faulty
gate-set is close to some representation of the Clifford group, an RB sequence
is described by the exponential decay of a process that has exactly two
eigenvalues close to one and the rest close to zero. This framework also allows
us to construct a gauge in which the average gate-set error is a depolarizing
channel parameterized by the RB decay rates, as well as a gauge which maximizes
the fidelity with respect to the ideal gate-set
From Bare Metal to Virtual: Lessons Learned when a Supercomputing Institute Deploys its First Cloud
As primary provider for research computing services at the University of
Minnesota, the Minnesota Supercomputing Institute (MSI) has long been
responsible for serving the needs of a user-base numbering in the thousands.
In recent years, MSI---like many other HPC centers---has observed a growing
need for self-service, on-demand, data-intensive research, as well as the
emergence of many new controlled-access datasets for research purposes. In
light of this, MSI constructed a new on-premise cloud service, named Stratus,
which is architected from the ground up to easily satisfy data-use agreements
and fill four gaps left by traditional HPC. The resulting OpenStack cloud,
constructed from HPC-specific compute nodes and backed by Ceph storage, is
designed to fully comply with controls set forth by the NIH Genomic Data
Sharing Policy.
Herein, we present twelve lessons learned during the ambitious sprint to take
Stratus from inception and into production in less than 18 months. Important,
and often overlooked, components of this timeline included the development of
new leadership roles, staff and user training, and user support documentation.
Along the way, the lessons learned extended well beyond the technical
challenges often associated with acquiring, configuring, and maintaining
large-scale systems.Comment: 8 pages, 5 figures, PEARC '18: Practice and Experience in Advanced
Research Computing, July 22--26, 2018, Pittsburgh, PA, US
Generation and detection of NOON states in superconducting circuits
NOON states, states between two modes of light of the form
allow for super-resolution interformetry. We
show how NOON states can be efficiently produced in circuit quntum
electrodynamics using superconducting phase qubits and resonators. We propose a
protocol where only one interaction between the two modes is required, creating
all the necessary entanglement at the start of the procedure. This protocol
makes active use of the first three states of the phase qubits. Additionally,
we show how to efficiently verify the success of such an experiment, even for
large NOON states, using randomly sampled measurements and semidefinite
programming techniques.Comment: 15 pages and 3 figure
Control of inhomogeneous atomic ensembles of hyperfine qudits
We study the ability to control d-dimensional quantum systems (qudits)
encoded in the hyperfine spin of alkali-metal atoms through the application of
radio- and microwave-frequency magnetic fields in the presence of
inhomogeneities in amplitude and detuning. Such a capability is essential to
the design of robust pulses that mitigate the effects of experimental
uncertainty and also for application to tomographic addressing of particular
members of an extended ensemble. We study the problem of preparing an arbitrary
state in the Hilbert space from an initial fiducial state. We prove that
inhomogeneous control of qudit ensembles is possible based on a semi-analytic
protocol that synthesizes the target through a sequence of alternating rf and
microwave-driven SU(2) rotations in overlapping irreducible subspaces. Several
examples of robust control are studied, and the semi-analytic protocol is
compared to a brute force, full numerical search. For small inhomogeneities, <
1%, both approaches achieve average fidelities greater than 0.99, but the brute
force approach performs superiorly, reaching high fidelities in shorter times
and capable of handling inhomogeneities well beyond experimental uncertainty.
The full numerical search is also applied to tomographic addressing whereby two
different nonclassical states of the spin are produced in two halves of the
ensemble
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