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At least 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Quantum utility-scale error mitigation for quantum quench dynamics in Heisenberg spin chains

Here, we implement a quantum error mitigation method termed self-mitigation, which is comparable to zero-noise extrapolation, at large scales to achieve quantum utility on near-term, noisy quantum computers. We investigate the effectiveness of several quantum error mitigation strategies, including self-mitigation, by simulating quantum quench dynamics for Heisenberg spin chains with system sizes up to 104 qubits using IBM quantum processors. In particular, we discuss the limitations of zero-noise extrapolation and the advantages offered by self-mitigation at large scales. The self-mitigation method demonstrates stable accuracy with large systems of 104 qubits comprising more than 3,000 CNOT gates. Also, we combine the discussed quantum error mitigation methods with practical entanglement entropy measuring methods, and it shows a good agreement with the theoretical estimation. Our study illustrates the usefulness of near-term noisy quantum hardware in examining the quantum quench dynamics of many-body systems at large scales and lays the groundwork for surpassing classical simulations with quantum methods prior to the development of fault-tolerant quantum computers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Quantum error mitigation by hidden inverses protocol in superconducting quantum devices

We present a method to improve the convergence of variational algorithms based on hidden inverses (HIs) to mitigate coherent errors. In the context of error mitigation, this means replacing the hardware implementation of certain Hermitian gates with their inverses. Doing so results in noise cancellation and a more resilient quantum circuit. This approach improves performance in a variety of two-qubit error models where the noise operator also inverts with the gate inversion. We apply the mitigation scheme on superconducting quantum processors running the variational quantum eigensolver (VQE) algorithm to find the H 2 ground-state energy. When implemented on superconducting hardware we find that the mitigation scheme effectively reduces the energy fluctuations in the parameter learning path in VQE, reducing the number of iterations for a converged value. We also provide a detailed numerical simulation of VQE performance under different noise models and explore how HIs and randomized compiling affect the underlying loss landscape of the learning problem. These simulations help explain our experimental hardware outcomes, helping to connect lower-level gate performance to application-specific behavior in contrast to metrics like fidelity which often do not provide an intuitive insight into observed high level performance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Error detection on quantum computers improving the accuracy of chemical calculations

The ultimate goal of quantum error correction is to achieve the fault-tolerance threshold beyond which quantum computers can be made arbitrarily accurate. This requires extraordinary resources and engineering efforts. We show that even without achieving full fault-tolerance, quantum error detection is already useful on the current generation of quantum hardware. We demonstrate this by executing an end-to-end chemical calculation for the hydrogen molecule encoded in the [[4, 2, 2]] quantum error-detecting code. The encoded calculation with logical qubits significantly improves the accuracy of the molecular ground-state energy.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Extending quantum probabilistic error cancellation by noise scaling

Here, we propose a general framework for quantum error mitigation that combines and generalizes two techniques: probabilistic error cancellation (PEC) and zero-noise extrapolation (ZNE). Similar to PEC, the proposed method represents ideal operations as linear combinations of noisy operations that are implementable on hardware. However, instead of assuming a fixed level of hardware noise, we extend the set of implementable operations by noise scaling. By construction, this method encompasses both PEC and ZNE as particular cases and allows us to investigate a larger set of hybrid techniques. For example, gate extrapolation can be used to implement PEC without requiring knowledge of the device’s noise model, e.g., avoiding gate-set tomography. Alternatively, probabilistic error reduction can be used to estimate expectation values at intermediate virtual noise strengths (below the hardware level), leading to partially mitigated results at a lower sampling cost. Moreover, multiple results obtained with different noise-reduction factors can be further postprocessed with ZNE to better approximate the zero-noise limit.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Computationally efficient zero-noise extrapolation for quantum-gate-error mitigation

Zero noise extrapolation (ZNE) is a widely used technique for gate error mitigation on near term quantum computers because it can be implemented in software and does not require knowledge of the quantum computer noise parameters. Traditional ZNE requires a significant resource overhead in terms of quantum operations. A recent proposal using a targeted (or random) instead of fixed identity insertion method (riim versus fiim) requires significantly fewer quantum gates for the same formal precision. We start by showing that riim can allow for ZNE to be deployed on deeper circuits than fiim but requires many more measurements to maintain the same statistical uncertainty. We develop two extensions to fiim and riim. The List Identity Insertion Method (liim) allows to mitigate the error from certain cnot gates, typically those with the largest error. Set Identity Insertion Method (siim) naturally interpolates between the measurement-efficient fiim and the gate-efficient riim allowing to trade off fewer cnot gates for more measurements. Finally, we investigate a way to boost the number of measurements, namely to run ZNE in parallel, utilizing as many quantum devices as are available. We explore the performance of riim in a parallel setting where there is a non-trivial spread in noise across sets of qubits within or across quantum computers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2011

Efficiency of dynamical decoupling sequences in the presence of pulse errors

For a generic dynamical decoupling sequence employing a single-axis control, we study its efficiency in the presence of small errors in the direction of the controlling pulses. In the case that the corresponding ideal dynamical decoupling sequence produces sufficiently good results, the impact of the errors is found to scale as {xi}{sup 2}, with negligible first-order effect, where {xi} is the dispersion of the random errors. This analytical prediction is numerically tested in a model in which the environment is modeled by one qubit coupled to a quantum kicked rotator in chaotic motion. In this model, with periodic pulses applied to the qubit in the environment, it is found numerically that periodic bang-bang control may outperform Uhrig dynamical decoupling.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

NP-hardness of decoding quantum error-correction codes

Although the theory of quantum error correction is intimately related to classical coding theory and, in particular, one can construct quantum error-correction codes (QECCs) from classical codes with the dual-containing property, this does not necessarily imply that the computational complexity of decoding QECCs is the same as their classical counterparts. Instead, decoding QECCs can be very much different from decoding classical codes due to the degeneracy property. Intuitively, one expects degeneracy would simplify the decoding since two different errors might not and need not be distinguished in order to correct them. However, we show that general quantum decoding problem is NP-hard regardless of the quantum codes being degenerate or nondegenerate. This finding implies that no considerably fast decoding algorithm exists for the general quantum decoding problems and suggests the existence of a quantum cryptosystem based on the hardness of decoding QECCs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

One-step error correction for multipartite polarization entanglement

We present two economical one-step error-correction protocols for multipartite polarization-entangled systems in a Greenberger-Horne-Zeilinger state. One uses spatial entanglement to correct errors in the polarization entanglement of an N-photon system, resorting to linear optical elements. The other uses frequency entanglement to correct errors in the polarization entanglement of an N-photon system. The parties in quantum communication can obtain a maximally entangled state from each N-photon system transmitted with one step in these two protocols, and both of their success probabilities are 100%, in principle. That is, they both work in a deterministic way, and they do not largely consume the less-entangled photon systems, which is far different from conventional multipartite entanglement purification schemes. These features may make these two protocols more useful for practical applications in long-distance quantum communication.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Decoherence and dephasing errors caused by the dc Stark effect in rapid ion transport

We investigate the error due to the dc Stark effect for quantum information processing for trapped ion quantum computers using the scalable architecture proposed in D. Wineland et al. [J. Res. Natl. Inst. Stand. Technol. 103, 259 (1998)] and D. Kielpinski et al. [Nature (London) 417, 709 (2002)]. As the operational speed increases, dephasing and decoherence due to the dc Stark effect become prominent as a large electric field is applied for rapidly transporting ions. We estimate the relative significance of the decoherence and dephasing effects and find that the latter is dominant. We find that the minimum possible dephasing is quadratic in the length of a trap and an inverse cubic in the operational time scale. From these relations, we obtain the operational speed range at which the shifts, caused by the dc Stark effect, are no longer negligible, no matter on which trajectory the ion is transported. Without phase correction, the shortest time a qubit can be transferred across a 100-micrometer-long trap, without excessive error, is about 10 ns for a {sup 40}Ca{sup +} ion and 50 ps for a {sup 9}Be{sup +} ion. In practice, the accumulated error is difficult to track and to calculate; thus, our paper gives an estimate for the range of the speed limit imposed by the dc Stark effect.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Experimental quantum error correction with high fidelity

More than ten years ago a first step toward quantum error correction (QEC) was implemented [Phys. Rev. Lett. 81, 2152 (1998)]. The work showed there was sufficient control in nuclear magnetic resonance to implement QEC, and demonstrated that the error rate changed from {epsilon} to {approx}{epsilon}{sup 2}. In the current work we reproduce a similar experiment using control techniques that have been since developed, such as the pulses generated by gradient ascent pulse engineering algorithm. We show that the fidelity of the QEC gate sequence and the comparative advantage of QEC are appreciably improved. This advantage is maintained despite the errors introduced by the additional operations needed to protect the quantum states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Reducing sequencing complexity in dynamical quantum error suppression by Walsh modulation

We study dynamical error suppression from the perspective of reducing sequencing complexity, with an eye toward facilitating the development of efficient semiautonomous quantum-coherent systems. To this end, we focus on digital sequences where all interpulse time periods are integer multiples of a minimum clock period and compatibility with digital classical control circuitry is intrinsic. We use so-called Walsh functions as a unifying mathematical framework; the Walsh functions are an orthonormal set of basis functions which may be associated directly with the control propagator for a digital modulation scheme. Using this insight, we characterize the suite of resulting Walsh dynamical decoupling sequences--including both familiar and novel control sequences--and identify the number of periodic square-wave (Rademacher) functions required to generate the associated Walsh function as the key determinant of the error-suppressing features. We also show how Walsh modulation may be employed for the protection of certain nontrivial logic gates. Based on these insights, we identify Walsh modulation as a digital-efficient approach for physical-layer error suppression.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Intermediate-mass-ratio inspirals in the Einstein Telescope. II. Parameter estimation errors

We explore the precision with which the Einstein Telescope will be able to measure the parameters of intermediate-mass-ratio inspirals, i.e., the inspirals of stellar mass compact objects into intermediate-mass black holes (IMBHs). We calculate the parameter estimation errors using the Fisher Matrix formalism and present results of Monte Carlo simulations of these errors over choices for the extrinsic parameters of the source. These results are obtained using two different models for the gravitational waveform which were introduced in paper I of this series. These two waveform models include the inspiral, merger, and ringdown phases in a consistent way. One of the models, based on the transition scheme of Ori and Thorne [A. Ori and K. S. Thorne, Phys. Rev. D 62, 124022 (2000)], is valid for IMBHs of arbitrary spin; whereas, the second model, based on the effective-one-body approach, has been developed to cross-check our results in the nonspinning limit. In paper I of this series, we demonstrated the excellent agreement in both phase and amplitude between these two models for nonspinning black holes, and that their predictions for signal-to-noise ratios are consistent to within 10%. We now use these waveform models to estimate parameter estimation errors for binary systems with masses 1.4M{sub {circle_dot}}+100M{sub {circle_dot}}, 10M{sub {circle_dot}}+100M{sub {circle_dot}}, 1.4M{sub {circle_dot}}+500M{sub {circle_dot}}, and 10M{sub {circle_dot}}+500M{sub {circle_dot}} and various choices for the spin of the central IMBH. Assuming a detector network of three Einstein Telescopes, the analysis shows that for a 10M{sub {circle_dot}} compact object inspiralling into a 100M{sub {circle_dot}} IMBH with spin q=0.3, detected with a signal-to-noise ratio of 30, we should be able to determine the compact object and IMBH masses, and the IMBH spin magnitude to fractional accuracies of {approx}10{sup -3}, {approx}10{sup -3.5}, and {approx}10{sup -3}, respectively. We also expect to determine the location of the source in the sky and the luminosity distance to within {approx}0.003 steradians and {approx}10%, respectively. We also compute results for several different possible configurations of the detector network to assess how the precision of parameter determination depends on the network configuration.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Self-calibration strategies for reducing systematic slope measurement errors of autocollimators in deflectometric profilometry

Deflectometric profilometers are used to precisely measure the form of beam shaping optics of synchrotrons and X-ray free-electron lasers. They often utilize autocollimators which measure slope by evaluating the displacement of a reticle image on a detector. Based on our privileged access to the raw image data of an autocollimator, novel strategies to reduce the systematic measurement errors by using a set of overlapping images of the reticle obtained at different positions on the detector are discussed. It is demonstrated that imaging properties such as, for example, geometrical distortions and vignetting, can be extracted from this redundant set of images without recourse to external calibration facilities. This approach is based on the fact that the properties of the reticle itself do not change – all changes in the reticle image are due to the imaging process. Firstly, by combining interpolation and correlation, it is possible to determine the shift of a reticle image relative to a reference image with minimal error propagation. Secondly, the intensity of the reticle image is analysed as a function of its position on the CCD and a vignetting correction is calculated. Thirdly, the size of the reticle image is analysed as a function of its position and an imaging distortion correction is derived. It is demonstrated that, for different measurement ranges and aperture diameters of the autocollimator, reductions in the systematic errors of up to a factor of four to five can be achieved without recourse to external measurements.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

SZ3: A Modular Framework for Composing Prediction-Based Error-Bounded Lossy Compressors

Today's scientific simulations require a significant reduction of data volume because of extremely large amounts of data they produce and the limited I/O bandwidth and storage space. Here, error-bounded lossy compression has been considered one of the most effective solutions to the above problem. In practice, however, the best-fit compression method often needs to be customized or optimized in particular because of diverse characteristics in different datasets and various user requirements on the compression quality and performance. In this paper, we address this issue with a novel modular, composable compression framework named SZ3. Our contributions are four-folds. (1) We develop SZ3 which features an innovative modular abstraction for the prediction-based compression framework, such that compression modules can be plugged in easily to create new compressors based on characteristics of data and user requirements. (2) We create a new compression pipeline by SZ3 for GAMESS data, which significantly improves the compression ratios over state-of-the-art compressors. (3) We develop an adaptive compression pipeline by SZ3 for APS data with minimal efforts, which leads to the best rate-distortion among all existing error-bounded lossy compressors for any bit-rate. (4) We compare the sustainability of SZ3 with leading error-bounded prediction-based compressors, and then demonstrate the necessity of diverse pipelines by integrating and evaluating several compression pipelines on diverse scientific datasets from multiple disciplines. Experiments show that SZ3 incurs very limited overhead in compressor integration and our customized compression pipelines lead to up to 20% improvement in compression ratios under the same data distortion, when compared with the best existing approach.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

Layer-Dependent Bit Error Variation in 3-D NAND Flash Under Ionizing Radiation

In this paper, we studied the total ionization dose (TID) effects on the multilevel-cell (MLC) 3-D NAND flash memory using Co-60 gamma radiation. We found a significant page-to-page bit error variation within a physical memory block of the irradiated memory chip. Our analysis showed that the origin of the bit error variation is the unique vertical layer-dependent TID response of the 3-D NAND. We found that the memory pages located at the upper and lower layers of the 3-D stack show higher fails compared to the middle-layer pages of a given memory block. We confirmed our findings by comparing radiation response of four different chips of the same specification. In addition, we compared the TID response of the MLC 3-D NAND with that of the 2-D NAND chip, which showed less page-to-page variation in bit error within a given memory block. We discuss the possible application of our findings for the radiation-tolerant smart memory controller design.

3-D NAND flash↗
DOE OSTI2017

Optimization of Error-Bounded Lossy Compression for Hard-to-Compress HPC Data

Since today’s scientific applications are producing vast amounts of data, compressing them before storage/transmission is critical. Results of existing compressors show two types of HPC data sets: highly compressible and hard to compress. In this work, we carefully design and optimize the error-bounded lossy compression for hard-tocompress scientific data. We propose an optimized algorithm that can adaptively partition the HPC data into best-fit consecutive segments each having mutually close data values, such that the compression condition can be optimized. Another significant contribution is the optimization of shifting offset such that the XOR-leading-zero length between two consecutive unpredictable data points can be maximized. We finally devise an adaptive method to select the best-fit compressor at runtime for maximizing the compression factor. We evaluate our solution using 13 benchmarks based on real-world scientific problems, and we compare it with 9 other state-of-the-art compressors. Experiments show that our compressor can always guarantee the compression errors within the user-specified error bounds. Most importantly, our optimization can improve the compression factor effectively, by up to 49% for hard-tocompress data sets with similar compression/decompression time cost.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2011

An approach for online evaluations of dose consequences caused by small rotational setup errors in intracranial stereotactic radiation therapy

Purpose: The purpose of this work is to investigate the impact of small rotational errors on the magnitudes and distributions of spatial dose variations for intracranial stereotactic radiotherapy (SRT) treatment setups, and to assess the feasibility of using the original dose map overlaid with rotated contours (ODMORC) method as a fast, online evaluation tool to estimate dose changes (using DVHs) to clinical target volumes (CTVs) and organs-at-risks (OARs) caused by small rotational setup errors. Methods: Fifteen intracranial SRT cases treated with either three-dimensional conformal radiation therapy (3DCRT) or intensity-modulated radiation therapy (IMRT) techniques were chosen for the study. Selected cases have a variety of anatomical dimensions and pathologies. Angles of {+-}3 deg. and {+-}5 deg. in all directions were selected to simulate the rotational errors. Dose variations in different regions of the brain, CTVs, and OARs were evaluated to illustrate the various spatial effects of dose differences before and after rotations. DVHs accounting for rotations that were recomputed by the treatment planning system (TPS) and those generated by the ODMORC method were compared. A framework of a fast algorithm for multicontour rotation implemented by ODMORC is introduced as well. Results: The average values of relative dose variations between original dose and recomputed dose accounting for rotations were greater than 4.0% and 10.0% in absolute mean and in standard deviation, respectively, at the skull and adjacent regions for all cases. They were less than 1.0% and 2.5% in absolute mean and in standard deviation, respectively, for dose points 3 mm away from the skull. The results indicated that spatial dose to any part of the brain organs or tumors separated from the skull or head surface would be relatively stable before and after rotations. Statistical data of CTVs and OARs indicate the lens and cochleas have the large dose variations before and after rotations, whereas the remaining ROIs have insignificant dose differences. DVH comparisons suggest that the ODMORC method is able to estimate the DVH of CTVs fairly accurately (within 1.5% of relative dose differences for evaluation volumes). The results also show that most of the OARs including the brain stem, spinal cord, chiasm, hippocampuses, optic nerves, and retinas, which were relatively distal from the skull and surface, had good agreement (within 2.0% of relative dose differences for 0.1 cc of the volumes ) between the ODMORC method and the recomputation, whereas OARs more proximate to the bone-tissue interface or surface, such as the lenses and cochlea, had larger dose variations (greater than 5.0%) for some cases due to the incapability of the ODMORC to account for scatter contribution variations proximate to interfaces and intrinsic dose calculation uncertainties for ROIs with small volumes. Conclusions: The ODMORC method can be implemented as an online evaluation system for rotation-induced dose changes of CTVs and most OARs and for other related dose consequence analyses.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Technical Note: Contrast solution density and cross section errors in inhomogeneity-corrected dose calculation for breast balloon brachytherapy

Purpose: Recent recommendations by the American Association of Physicists in Medicine Task Group 186 emphasize the importance of understanding material properties and their effect on inhomogeneity-corrected dose calculation for brachytherapy. Radiographic contrast is normally injected into breast brachytherapy balloons. In this study, the authors independently estimate properties of contrast solution that were expected to be incorrectly specified in a commercial brachytherapy dose calculation algorithm. Methods: The mass density and atomic weight fractions of a clinical formulation of radiographic contrast solution were determined using manufacturers' data. The mass density was verified through measurement and compared with the density obtained by the treatment planning system's CT calibration. The atomic weight fractions were used to determine the photon interaction cross section of the contrast solution for a commercial high-dose-rate (HDR) brachytherapy source and compared with that of muscle. Results: The density of contrast solution was 10% less than that obtained from the CT calibration. The cross section of the contrast solution for the HDR source was 1.2% greater than that of muscle. Both errors could be addressed by overriding the density of the contrast solution in the treatment planning system. Conclusions: The authors estimate the error in mass density and cross section parameters used by a commercial brachytherapy dose calculation algorithm for radiographic contrast used in a clinical breast brachytherapy practice. This approach is adaptable to other clinics seeking to evaluate dose calculation errors and determine appropriate density override values if desired.

60 APPLIED LIFE SCIENCES↗