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The Large Hadron Collider will soon undergo an upgrade to increase its luminosity by a factor of ~10 [1]. A crucial part of this upgrade will be replacement of the NbTi focusing magnets with Nb3Sn magnets that achieve a ~50% increase in the field strength. This will be the first ever large-scale implementation of Nb3Sn magnets in a particle accelerator. The High-Luminosity LHC Upgrade, HL-LHC is a CERN project with a world-wide collaboration. It is under construction and utilizes Nb3Sn Magnets (named MQXF) as key ingredients to increase tenfold the integrated luminosity delivered to the CMS and ATLAS experiments in the next decade. The HL-LHC AUP is the US effort to contribute approximately 50% of the low-beta focusing magnets and crab cavities for the HL-LHC. This paper will present the program to fabricate the Nb3Sn superconducting magnets. We are reporting the status of the HL-LHC AUP project present the results from horizontal tests of the first fully assembled cryo-assembly., Comment: IPAC'24 - 15th International Particle Accelerator Conference

By the end of October 2022, the US HL-LHC Accelerator Upgrade Project (AUP) had completed fabrication of ten MQXFA magnets and tested eight of them. The MQXFA magnets are the low beta quadrupole magnets to be used in the Q1 and Q3 Inner Triplet elements of the High Luminosity LHC. This AUP effort is shared by BNL, Fermilab, and LBNL, with strand verification tests at NHMFL. An important step of the AUP QA plan is the testing of MQXFA magnets in a vertical cryostat at BNL. The acceptance criteria that could be tested at BNL were all met by the first four production magnets (MQXFA03-MQXFA06). Subsequently, two magnets (MQXFA07 and MQXFA08) did not meet some criteria and were disassembled. Lessons learned during the disassembly of MQXFA07 caused a revision to the assembly specifications that were used for MQXFA10 and subsequent magnets. In this paper, we present a summary of: 1) the fabrication and test data of all the MQXFA magnets; 2) the analysis of MQXFA07/A08 test results with characterization of the limiting mechanism; 3) the outcome of the investigation, including the lessons learned during MQXFA07 disassembly; and 4) the finite element analysis correlating observations with test performance.

Many companies and institutions have automated their business process in workflow management software. The novel programming paradigm Task-Oriented Programming (TOP) provides an abstraction for such software. The largest framework based on TOP, iTasks, has been used to develop real-world software. Workflow software often includes critical systems. In such cases it is important to reason over the software to ascertain its correctness. The lack of a formal iTasks semantics makes it unsuitable for formal reasoning. To this end TopHat has been developed as a TOP language with a formal semantics. However, TopHat lacks a graphical user interface (GUI), making it harder to develop practical TopHat systems. In this paper we present TopHat UI. By combining an existing server framework and user interface framework, we have developed a fully functioning proof of concept implementation in Haskell, on top of TopHat's semantics. We show that implementing a TOP framework is possible using a different host language than iTasks uses. None of TopHat's formal properties have been compromised, since the UI framework is completely separate from TopHat. We run several example programs and evaluate their generated GUI. Having such a system improves the quality and verifiability of TOP software in general.

Automatic exploit generation is a relatively new area of research. Work in this area aims to automate the manual and labor intensive task of finding exploits in software. In this paper we present a novel program logic to support automatic exploit generation. We develop a program logic called Reachability Logic, which formally defines the relation between reachability of an assertion and the preconditions which allow them to occur. This relation is then used to calculate the search space of preconditions. We show that Reachability Logic is a powerful tool in automatically finding evidence that an assertion is reachable. We verify that the system works for small litmus tests, as well as real-world algorithms. An implementation has been developed, and the entire system is proven to be sound and complete in a theorem prover. This work represents an important step towards formally verified automatic exploit generation.

Colliders are built on a foundation of superconducting magnet technology that provides strong dipole magnets to maintain the beam orbit and strong focusing magnets to enable the extraordinary luminosity required to probe physics at the energy frontier. The dipole magnet strength plays a critical role in dictating the energy reach of a collider, and the superconducting magnets are arguably the dominant cost driver for future collider facilities. As the community considers opportunities to explore new energy frontiers, the importance of advanced magnet technology - both in terms of magnet performance and in the magnet technology's potential for cost reduction - is evident, as the technology status is essential for informed decisions on targets for physics reach and facility feasibility., Comment: contribution to Snowmass 2021

The MQXFA Quadrupole magnets will be installed in High Luminosity LHC to form the Q1 and Q3 inner triplet optical elements in front of the interaction points 1 (ATLAS) and 5 (CMS). A pair of MQXFA units is assembled in a stainless steel helium vessel, including the end domes, to make the Q1 Cold Mass or the Q3 Cold Mass. The US HL LHC Accelerator Upgrade Project* is responsible for the design, manufacturing and test of the Q1/Q3 Cold Masses and the complete MQXFA magnets. CERN provides the cryostat components and is responsible for integration and installation in HL LHC. The MQXFA quadrupoles have 150 mm aperture, 4.2 m magnetic length, nominal gradient of 132.2 T/m, and coil peak field of 11.3 T. They use Nb_3Sn conductor and a support structure made of segmented aluminum shells pre-loaded by using bladders and keys. This report presents the final design of the MQXFA quadrupole magnets. *Supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, Comment: 120 pages

One of the main bottlenecks in the pursuit of a large-scale--chip-based quantum computer is the large number of control signals needed to operate qubit systems. As system sizes scale up, the number of terminals required to connect to off-chip control electronics quickly becomes unmanageable. Here, we discuss a quantum-dot spin-qubit architecture that integrates on-chip control electronics, allowing for a significant reduction in the number of signal connections at the chip boundary. By arranging the qubits in a two-dimensional (2D) array with $\sim$12 $\mu$m pitch, we create space to implement locally integrated sample-and-hold circuits. This allows to offset the inhomogeneities in the potential landscape across the array and to globally share the majority of the control signals for qubit operations. We make use of advanced circuit modeling software to go beyond conceptual drawings of the component layout, to assess the feasibility of the scheme through a concrete floor plan, including estimates of footprints for quantum and classical electronics, as well as routing of signal lines across the chip using different interconnect layers. We make use of local demultiplexing circuits to achieve an efficient signal-connection scaling leading to a Rent's exponent as low as $p = 0.43$. Furthermore, we use available data from state-of-the-art spin qubit and microelectronics technology development, as well as circuit models and simulations, to estimate the operation frequencies and power consumption of a million-qubit processor. This work presents a novel and complementary approach to previously proposed architectures, focusing on a feasible scheme to integrating quantum and classical hardware, and significantly closing the gap towards a fully CMOS-compatible quantum computer implementation., Comment: 19 pages, 16 figures

We analyze the structure and evolution of ribbons from the M7.3 SOL2014-04-18T13 flare using ultraviolet (UV) images from IRIS and SDO/AIA, magnetic data from SDO/HMI, hard X-ray (HXR) images from RHESSI, and light curves from Fermi/GBM, in order to infer properties of coronal magnetic reconnection. As the event progresses, two flare ribbons spread away from the magnetic polarity inversion line. The width of the newly brightened front along the extension of the ribbon is highly intermittent in both space and time, presumably reflecting non-uniformities in the structure and/or dynamics of the flare current sheet. Furthermore, the ribbon width grows most rapidly in regions exhibiting concentrated non-thermal HXR emission, with sharp increases slightly preceding the HXR bursts. The light curve of the ultraviolet emission matches the HXR light curve at photon energies above 25 keV. In other regions the ribbon-width evolution and light curves do not temporally correlate with the HXR emission. This indicates that the production of non-thermal electrons is highly non-uniform within the flare current sheet. Our results suggest a strong connection between the production of non-thermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts, which in turn reflects inhomogeneous structure and/or reconnection dynamics of the current sheet. Despite this variability, the ribbon fronts remain nearly continuous, quasi-one-dimensional features. Thus, although the reconnecting coronal current sheets are highly structured, they remain quasi-two-dimensional and the magnetic energy release occurs systematically, rather than stochastically, through the volume of reconnecting magnetic flux.

Quantum computational experiments exploiting Noisy Intermediate-Scale Quantum (NISQ) devices to demonstrate violation of a Bell inequality are proposed. They consist of running specified quantum algorithms on few-qubit computers. If such a device assures entanglement and performs single-shot measurements, the detection loophole is avoided. Four concise quantum circuits determining the expectation values of the relevant observables are used for a two-qubit system. It is possible to add an ancilla qubit to these circuits and eventually only measure the ancilla to obtain the relevant information. For a four-qubit NISQ computer, two algorithms yielding the same averages, however also guaranteeing a random choice of the observable, are developed. A freedom-of-choice loophole is therefore avoided. Including an additional ancilla reduces the number of measurements by one since in this case only the ancillas need to be measured. Note that these methods, using the NISQ device, are intrinsically quantum mechanical. Locality loopholes cannot be excluded on present NISQ systems. Results of simulations on the QX simulator of Quantum Inspire are presented. The Bell inequality is indeed found to be violated, even if some additional noise is included by means of the depolarizing channel error model. The algorithms have been implemented on the IBM Q Experience as well. The results of these quantum computations support a violation of the Bell inequality by various standard deviations., Comment: corrected typos, minor textual adjustments, results unchanged

It is often more complicated to measure the phase response of a large system than the magnitude. In that case, one can attempt to use the Kramers-Kronig (KK) relations for magnitude and phase, which relates magnitude and phase analytically. The advantage is that then only the magnitude of the frequency response needs to be measured. We show that the KK relations for magnitude and phase may yield invalid results when the transfer function has zeros located in the right half of the complex s-plane, i.e. the system is non-minimum phase. In this paper we propose a method which enables to determine these zeros, by using specific excitation signals and measuring the resulting time responses of the system. The method is verified using blind tests among the authors. When the locations of the zeros in the right half of the complex s-plane are known, modified KK relations can be successfully applied to non-minimum phase systems. We demonstrate this by computing the phase response of the electric field, excited by a point dipole source inside a closed cavity with Perfect Electrically Conducting (PEC) walls. Also, the effects of simulated measurement noise are considered for this example., Comment: This is a preprint version of the final publication

Noisy Intermediate-Scale Quantum computers are expected to be available this year. It is proposed to exploit such a device for decision making under uncertainty. The probabilistic character of quantum mechanics reflects this uncertainty. Concomitantly, the noise may add to it. The approach is standard in the sense that Bayes decision rule is used to decide on the basis of maximum expected reward. The novelty is to model the various action profiles and the development of `nature' as unitary transformations on a set of qubits. Measurement eventually yields samples of classical binary random variables in which the reward function has to be expressed. In order to achieve sufficiently low variances for reliable decision making more runs of such a quantum algorithm are necessary. Some simple examples have been worked out to elucidate the idea. Here the calculations are still analytically feasible. Presently lacking an operating quantum device, the QX simulator of Quantum Inspire has been used to generate the necessary samples for comparison and demonstration. First obtained results are promising and point at a possible useful application for noisy intermediate-scale quantum computers., Comment: 13 pages, 10 figures

Four electron spin qubits in quantum dots are studied by means of an exchange interaction Hamiltonian. The time-independent Schr\"odinger equation is exactly analytically solved for the symmetric case, that is equal qubit frequencies and equal couplings. The spin system can be used as two data-qubits and two ancillas, thereby realizing a $X$ and $Z$ stabilizing circuit exploited in error correction and surface codes. The unitary evolution of corresponding stable states is calculated and consequences for error syndromes and fidelities are assessed. It is also shown that applying the evolution operator for a prescribed duration and subsequent measurement of the ancillas lead to a `verifiable' two-qubit phase gate., Comment: 10 pages, 5 figures

Surface codes based on stabilizer circuits may pave the way for large scale fault-tolerant quantum computation. The surface code uses only single- and two-qubit gates and the error threshold falls close to 1% for a large range of errors. Among the most promising candidates to physically implement such circuits and codes are superconducting qubits coupled by resonators. We investigate a X and Z stabilizing circuit realized by two data qubits, two ancillas and four resonators. The aim is to assess the consequences of unitary evolution of the interacting system, in particular for given stable initial states, on fidelities and error syndrome probabilities. We model the system with a Jaynes-Tavis-Cummings Hamiltonian and construct the low-excitation level evolution operators. The analysis is limited to two stable input states. We assume an ideal system with perfect gates, perfect measurements and no decoherence or leakage. Our analysis shows that the capture probabilities after the execution of a single stabilizer round are not equal to 100%, but vary between 99.2% and 99.99%. This is caused solely by the unitary evolution of the interacting system. Two consecutive rounds of stabilizer measurements result in capture probability values that depend heavily on the duration of the evolution, but vary between 0% and 99%. Also due to the unitary evolution, the final state of the data qubits leaves the the four-dimensional subspace, which results in a state fidelity oscillating between 0 and 1. Even if an error on the qubits is captured, the correcting operation on the qubit will not bring the qubit to the original state. The errors induced by the Hamiltonian evolution of the system cannot be interpreted nor classified as commonly appearing errors. Additional or augmented quantum error correction may be required to compensate these effects of resonator-qubit interaction., Comment: 21 pages, 12 figures

In this study, we develop a semi-analytical framework to solve generalized Jaynes-Tavis-Cummings Hamiltonians describing multi-qudit systems coupled via EM resonators. Besides the multi-level generalization we allow for an arbitrary number of resonators and/or modes, with nonidentical couplings to the qudits. Our method is based on generic excitation-number operators which commute with the respective Hamiltonians in the rotating wave approximation (RWA). The validity of the RWA is assessed explicitly. The formalism enables the study of eigenstates, eigenenergies and corresponding time evolutions of such coupled multi-qudit systems. The technique can be applied in cavity quantum electrodynamics and circuit quantum electrodynamics. It is also applicable to atomic physics, describing the coupling of a single-mode photon to an atom. As an example, we solve the Schr\"odinger equation for a two-qubit-one-resonator system, in principle to arbitrary high excitations. We also solve the Tavis-Cummings Hamiltonian in the one-excitation subspace for an arbitrary number of identical qubits resonantly coupled to one resonator. As a final example, we calculate of the low-excitation spectrum of a coupled two-transmon system., Comment: 11 pages, 4 figures v2&3. Corrected type in abstract (rotating frame --> rotating wave)

A stratified sampling plan to audit health insurance claims is offered. The stratification is by dollar amount of the claim. The plan is representative in the sense that with high probability for each stratum, the difference in the average dollar amount of the claim in the sample and the average dollar amount in the population, is ``small.'' Several notions of ``small'' are presented. The plan then yields a relatively small total sample size with the property that the overall average dollar amount in the sample is close to the average dollar amount in the population. Three different estimators and corresponding lower confidence bounds for over (under) payments are studied., Comment: Published at http://dx.doi.org/10.1214/074921707000000094 in the IMS Lecture Notes Monograph Series (http://www.imstat.org/publications/lecnotes.htm) by the Institute of Mathematical Statistics (http://www.imstat.org)

An important predicted, but so far uncharacterized, property of the new superconductor MgB2 is electronic anisotropy arising from its layered crystal structure. Here we report on three c-axis oriented thin films, showing that the upper critical field anisotropy ratio Hc2par/Hc2perp is 1.8 to 2.0, the ratio increasing with higher resistivity. Measurements of the magnetic field-temperature phase diagram show that flux pinning disappears at H* ~ 0.8Hc2perp(T) in untextured samples. Hc2par(0) is strongly enhanced by alloying to 39 T for the highest resistivity film, more than twice that seen in bulk samples., Comment: 5 pages Acrobat 3.02 pdf

The discovery of superconductivity at 39 K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. With twice the critical temperature of Nb_3Sn and four times that of Nb-Ti alloy, MgB_2 has the potential to reach much higher fields and current densities than either of these technological superconductors. A vital prerequisite, strongly linked current flow, has already been demonstrated even at this early stage. One possible drawback is the observation that the field at which superconductivity is destroyed is modest. Further, the field which limits the range of practical applications, the irreversibility field H*(T), is ~7 T at liquid helium temperature (4.2 K), significantly lower than ~10 T for Nb-Ti and ~20 T for Nb_3Sn. Here we show that MgB_2 thin films can exhibit a much steeper temperature dependence of H*(T) than is observed in bulk materials, yielding H*(4.2 K) above 14 T. In addition, very high critical current densities at 4.2 K, 1 MA/cm_2 at 1 T and 10_5 A/cm_2 at 10 T, are possible. These data demonstrate that MgB_2 has credible potential for high-field superconducting applications., Comment: 4 pages pdf, submitted to Nature 3/20/01

The discovery of superconductivity at 39 K in MgB2[1] raises many issues. One of the central questions is whether this new superconductor resembles a high-temperature-cuprate superconductor or a low-temperature metallic superconductor in terms of its current carrying characteristics in applied magnetic fields. In spite of the very high transition temperatures of the cuprate superconductors, their performance in magnetic fields has several drawbacks[2]. Their large anisotropy restricts high bulk current densities to much less than the full magnetic field-temperature (H-T) space over which superconductivity is found. Further, weak coupling across grain boundaries makes transport current densities in untextured polycrystalline forms low and strongly magnetic field sensitive[3,4]. These studies of MgB2 address both issues. In spite of the multi-phase, untextured, nano-scale sub-divided nature of our samples, supercurrents flow throughout without the strong sensitivity to weak magnetic fields characteristic of Josephson-coupled grains[3]. Magnetization measurements over nearly all of the superconducting H-T plane show good temperature scaling of the flux pinning force, suggestive of a current density determined by flux pinning. At least two length scales are suggested by the magnetization and magneto optical (MO) analysis but the cause of this seems to be phase inhomogeneity, porosity, and minority insulating phase such as MgO rather than by weakly coupled grain boundaries. Our results suggest that polycrystalline ceramics of this new class of superconductor will not be compromised by the weak link problems of the high temperature superconductors, a conclusion with enormous significance for applications if higher temperature analogs of this compound can be discovered.

We compute the "+" component of the electromagnetic current of a composite spin-one two-fermion system for vanishing momentum transfer component $q^+=q^0+q^3$. In particular, we extract the nonvanishing pair production amplitude on the light-front. It is a consequence of the longitudinal zero momentum mode, contributing to the light-front current in the Breit-frame. The covariance of the current is violated, if such pair terms are not included in its matrix elements. We illustrate our discussion with some numerical examples., Comment: 17 pages,include 5 figures (lfcxx.eps, lfczx.eps,lfczz.eps, lfcagg.eps and lfcaqq.eps), use latex,epsf,elsart, e-mail: pacheco@lpnp66.in2p3.fr, tobias@fis.ita.cta.br, naus1@fel.tno.nl, sauer@itp.uni-hannover.de, Accepted in Nucl.Phys. A (1999)

The theory of the strong interactions, Quantum Chromodynamics (QCD), has been addressed by a variety of non-perturbative techniques over the decades since its introduction. We have investigated Hamiltonian formulations with different quantization methods and approximation schemes. In one method, we utilize light-front coordinates to investigate the role of bosonic zero modes in leading to confinement. In another method we are able to obtain spectra for the mesons and baryons using constituent quark masses but no phenomenological confinement. We survey our principal accomplishments to date and indicate our future directions., Comment: 19pp

The Ward-Takahashi identity, reflecting local gauge invariance, is perturbatively verified for a boson model in light front field theory. A careful integration over the light front energy, corresponding to exactly taking into account pair terms, which are the contributions of the zero longitudinal momentum mode, is crucial to obtain this result. Furthermore, the one-loop boson form factors are calculated for arbitrary off-shell momenta., Comment: 11 pages,include two figures (fig1.eps and fig2.eps), use latex,epsf e-mail: naus@itp.uni-hannover.de, pacheco@axpfep1.if.usp.br and tobias@fis.ita.cta.br Submitted to Few-Body Systems (1997)

The electromagnetic form factor of the pion is calculated in a pseudoscalar field theoretical model which constituent quarks. We extract the form factor using the "+" component of the electromagnetic current in the light-cone formalism. For comparison, we also compute the form factor in the covariant framework and we obtain perfect agreement. It is shown that the pair terms do not contribute in this pseudoscalar model. This explains why a naive light-cone calculation, i.e., omitting pair terms from the onset, also yields the same results., Comment: 11 pages,include figure (pion.eps), use latex,epsf e-mail: nau@itp.uni-hannover.de, pacheco@axpfep1.if.usp.br and tobias@fis.ita.cta.br Submitted to Phys.Letters. B (1997)

Starting from relativistic quantum field theories, describing interacting nucleons and pions coupled to the dynamical electromagnetic field, the pion degrees of freedom are eliminated by means of functional integration. Apart from taking into account some operators perturbatively in $e$, e.g. the vacuum polarization, this procedure is exact, giving effective theories for nucleons and photons. The subsequent nonrelativistic reduction yields the corresponding nonrelativistic quantum field theory. The latter is unique, irrespective of the precize form of the original nucleon-pion interaction. Nucleonic potentials and electromagnetic interactions are mutually consistent. Local gauge invariance is satisfied at any stage of the formal developments., Comment: 15 pages, LaTeX

Starting from the QCD Lagrangian, we present the QCD Hamiltonian for near light cone coordinates. We study the dynamics of the gluonic zero modes of this Hamiltonian. The strong coupling solutions serve as a basis for the complete problem. We discuss the importance of zero modes for the confinement mechanism., Comment: 32 pages, ReVTeX, 2 Encapsulated PostScript figures

The nonrelativistic Ward-Takahashi identity, a consequence of local gauge invariance in quantum mechanics, shows the necessity of exchange current contributions in case of nonlocal and/or isospin-dependent potentials. It also implies Siegert's hypothesis: in the nonrelativistic limit, two-body charge densities identically vanish. Neither current conservation, which follows from global gauge invariance, nor the constraints of (lowest order) relativity are sufficient to arrive at this result. Furthermore, a low-energy theorem for exchange contributions is established., Comment: 5 pages, REVTEX

We examine QED(3+1) quantised in the `front form' with finite `volume' regularisation, namely in Discretised Light-Cone Quantisation. Instead of the light-cone or Coulomb gauges, we impose the light-front Weyl gauge $A^-=0$. The Dirac method is used to arrive at the quantum commutation relations for the independent variables. We apply `quantum mechanical gauge fixing' to implement Gau{\ss}' law, and derive the physical Hamiltonian in terms of unconstrained variables. As in the instant form, this Hamiltonian is invariant under global residual gauge transformations, namely displacements. On the light-cone the symmetry manifests itself quite differently., Comment: LaTeX file, 30 pages (A4 size), no figures. Submitted to Physical review D. January 18, 1996. Originally posted, erroneously, with missing `Weyl' in title. Otherwise, paper is identical

We examine commonly used approaches to deal with the scattering of electrons from a bound nucleon. Several prescriptions are shown to be related by gauge transformations. Nevertheless, due to current non-conservation, they yield different results. These differences reflect the size of the uncertainty that persists in the interpretation of $(e,e'p)$ experiments., Comment: 6 pp (10 in preprint form), ReVTeX, (+ 4 figures, uuencoded)

We use a Gaussian wave functional for the ground state to reorder the Hamiltonian into a free part with a variationally determined mass and the rest. Once spontaneous symmetry breaking is taken into account, the residual Hamiltonian can, in principle, be treated perturbatively. In this scheme we analyze the $O(1)$ and $O(2)$ scalar models. For the $O(2)$--theory we first explicitly calculate the massless Goldstone excitation and then show that the one-loop corrections of the effective Hamiltonian do not generate a mass., Comment: 45 pages, 5 Figs., LaTeX, REPLACED VERSION CONTAINS NOW ONLY 80-CHARACTER LINES

The derivation of the `classical' low-energy theorem (LET) for \gamma p \rightarrow p\pi^0 is re-examined and compared to chiral perturbation theory. Both results are correct and are not contradictory; they differ because different expansions of the same quantity are involved. Possible modifications of the extended partially conserved axial-vector current relation, one of the starting points in the derivation of the LET, are discussed. An alternate, more transparent form of the LET is presented., Comment: 5 pages, Revtex, no figures, no tables

We introduce a new method to include condensates in the light-cone Hamiltonian. By using a Gaussian approximation to the ordinary vacuum in a theory close to the light front, we derive an effective Hamiltonian on the light cone, which has new terms reflecting the nontriviality of the vacuum. We demonstrate our method for scalar $\phi^4$-theory and the massive Schwinger model., Comment: 15 pages; LaTeX; local no. HD-TVP-94-7