791,112 research outputs found
Complete characterization of the directly implementable quantum gates used in the IBM quantum processors
Quantum process tomography of each directly implementable quantum gate used
in the IBM quantum processors is performed to compute gate error in order to
check viability of complex quantum operations in the superconductivity-based
quantum computers introduced by IBM and to compare the quality of these gates
with the corresponding gates implemented using other technologies. Quantum
process tomography (QPT) of C-NOT gates have been performed for three
configurations available in IBM QX4 processor. For all the other allowed gates
QPT have been performed for every allowed position (i.e., by placing the gates
in different qubit lines) for IBM QX4 architecture, and thus, gate fidelities
are obtained for both single-qubit and 2-qubit gates. Gate fidelities are
observed to be lower than the corresponding values obtained in the other
technologies, like NMR. Further, gate fidelities for all the single-qubit gates
are obtained for IBM QX2 architecture by placing the gates in the third qubit
line (). It's observed that the IBM QX4 architecture yields better gate
fidelity compared to IBM QX2 in all cases except the case of
gate as far as the gate fidelity corresponding to the third qubit line is
concerned. In general, the analysis performed here leads to a conclusion that a
considerable technological improvement would be inevitable to achieve the
desired scalability required for the realization of complex quantum operations.Comment: Quantum Process tomography has been done for all the gates used in
IBM QX2 and IBM QX
Regularities with random interactions in energy centroids defined by group symmetries
Regular structures generated by random interactions in energy centroids
defined over irreducible representations (irreps) of some of the group
symmetries of the interacting boson models IBM, IBM, IBM- and
IBM- are studied by deriving trace propagations equations for the
centroids. It is found that, with random interactions, the lowest and highest
group irreps in general carry most of the probability for the corresponding
centroids to be lowest in energy. This generalizes the result known earlier,
via numerical diagonalization, for the more complicated fixed spin ()
centroids where simple trace propagation is not possible.Comment: 18 pages, 3 figure
IBM Cloud Strategic Audit
An examination of IBM Cloud\u27s strategy and history and a recommendation for what to do moving forward
Inclusion body myositis: therapeutic approaches.
The idiopathic inflammatory myopathies are a heterogeneous group of diseases that include dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) and other less common myopathies. These are clinically and histopathologically distinct diseases with many shared clinical features. IBM, the most commonly acquired inflammatory muscle disease occurs in individuals aged over 50 years, and is characterized by slowly progressive muscle weakness and atrophy affecting proximal and distal muscle groups, often asymmetrically. Unlike DM and PM, IBM is typically refractory to immunotherapy. Although corticosteroids have not been tested in randomized controlled trials, the general consensus is that they are not efficacious. There is some suggestion that intravenous immunoglobulin slows disease progression, but its long-term effectiveness is unclear. The evidence for other immunosuppressive therapies has been derived mainly from case reports and open studies and the results are discouraging. Only a few clinical trials have been conducted on IBM, making it difficult to provide clear recommendations for treatment. Moreover, IBM is a slowly progressive disease so assessment of treatment efficacy is problematic due to the longer-duration trials needed to determine treatment effects. Newer therapies may be promising, but further investigation to document efficacy would be expensive given the aforementioned need for longer trials. In this review, various treatments that have been employed in IBM will be discussed even though none of the interventions has sufficient evidence to support its routine use
Synchronising C/C++ and POWER
Shared memory concurrency relies on synchronisation primitives: compare-and-swap, load-reserve/store-conditional (aka LL/SC), language-level mutexes, and so on. In a sequentially consistent setting, or even in the TSO setting of x86 and Sparc, these have well-understood semantics. But in the very relaxed settings of IBM®, POWER®, ARM, or C/C++, it remains surprisingly unclear exactly what the programmer can depend on.
This paper studies relaxed-memory synchronisation. On the hardware side, we give a clear semantic characterisation of the load-reserve/store-conditional primitives as provided by POWER multiprocessors, for the first time since they were introduced 20 years ago; we cover their interaction with relaxed loads, stores, barriers, and dependencies. Our model, while not officially sanctioned by the vendor, is validated by extensive testing, comparing actual implementation behaviour against an oracle generated from the model, and by detailed discussion with IBM staff. We believe the ARM semantics to be similar.
On the software side, we prove sound a proposed compilation scheme of the C/C++ synchronisation constructs to POWER, including C/C++ spinlock mutexes, fences, and read-modify-write operations, together with the simpler atomic operations for which soundness is already known from our previous work; this is a first step in verifying concurrent algorithms that use load-reserve/store-conditional with respect to a realistic semantics. We also build confidence in the C/C++ model in its own terms, fixing some omissions and contributing to the C standards committee adoption of the C++11 concurrency model
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