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Atom-loss errors are a major limitation of current state-of-the-art neutral-atom quantum computers and pose a significant challenge for scalable systems. In a quantum processor with cesium atoms, we demonstrate proof-of-principle circuit-based conversion of this form of leakage error to erasure errors via leakage-detection units (LDUs), which nondestructively map information about the presence or absence of the qubit onto the state of an ancilla. We benchmark the performance of the LDU using a three-outcome low-loss state-detection method and find that the LDU detects atom-loss errors with approximately 93.4% accuracy, limited by technical imperfections of our apparatus. We further compile and execute a swap LDU, wherein the roles of the original data atom and ancilla atom are exchanged under the action of the LDU, providing “free refilling” of atoms in the case of atom loss. This circuit-based leakage-to-erasure error conversion is a critical component of a neutral-atom quantum processor where the quantum information may significantly outlive the lifetime of any individual atom in the quantum register. Finally, we demonstrate that LDUs may also be used to handle other forms of leakage errors where population moves to states outside of the computational subspace.

We study the generation of two-qudit entangling quantum logic gates using two techniques in quantum optimal control. We take advantage of both continuous, Lie algebraic control and digital, Lie group control. In both cases, the key is access to a time-dependent Hamiltonian, which can generate an arbitrary unitary matrix in the group SU(d^{2}). We find efficient protocols for creating high-fidelity entangling gates. As a test of our theory, we study the case of qudits robustly encoded in nuclear spins of alkaline earth atoms and manipulated with magnetic and optical fields, with entangling interactions arising from the well-known Rydberg blockade. We applied this in a case study based on a d=10 dimensional qudit encoded in the I=9/2 nuclear spin in ^{87}Sr, controlled through a combination of nuclear spin resonance, a tensor ac-Stark shift, and Rydberg dressing, which allows us to generate an arbitrary symmetric entangling two-qudit gate, such as CPhase. Our techniques can be used to implement qudit entangling gates for any 2≤d≤10 encoded in the nuclear spin. We also studied how decoherence due to the finite lifetime of the Rydberg states affects the creation of the CPhase gate and found, through numerical optimization, a fidelity of 0.9985, 0.9980, 0.9942, and 0.9800 for d=2, d=3, d=5, and d=7, respectively. This provides a powerful platform to explore the various applications of quantum information processing of qudits, including metrological enhancement with qudits, quantum simulation, universal quantum computation, and quantum error correction.

We revisit well-known protocols in quantum metrology using collective spins and propose a unifying picture for optimal state preparation based on a semiclassical description in phase space. We show how this framework allows for quantitative predictions of the timescales required to prepare various metrologically useful states, and that these predictions remain accurate even for moderate system sizes, surprisingly far from the classical limit. Furthermore, this framework allows us to build a geometric picture that relates optimal (exponentially fast) entangled probe preparation to the existence of separatrices connecting saddle points in phase space. We illustrate our results with the paradigmatic examples of the two-axis countertwisting and twisting-and-turning Hamiltonians, where we provide analytical expressions for all the relevant optimal timescales. Finally, we propose a generalization of these models to include p-body collective interaction (or p-order twisting), beyond the usual case of p=2. Using our geometric framework, we prove a no-go theorem for the local optimality of these models for p>2.

We study the behavior of errors in the quantum simulation of spin systems with long-range multibody interactions resulting from the Trotter-Suzuki decomposition of the time-evolution operator. We identify a regime where the Floquet operator underlying the Trotter decomposition undergoes sharp changes even for small variations in the simulation step size. This results in a time evolution operator that is very different from the dynamics generated by the targeted Hamiltonian, which leads to a proliferation of errors in the quantum simulation. These regions of sharp change in the Floquet operator, referred to as structural instability regions, appear typically at intermediate Trotter step sizes and in the weakly interacting regime, and are thus complementary to recently revealed quantum chaotic regimes of the Trotterized evolution [L. M. Sieberer et al. npj Quantum Inf. 5, 78 (2019); M. Heyl, P. Hauke, and P. Zoller, Sci. Adv. 5, eaau8342 (2019)]. We characterize these structural instability regimes in p-spin models, transverse-field Ising models with all-to-all p-body interactions, and analytically predict their occurrence based on unitary perturbation theory. We further show that the effective Hamiltonian associated with the Trotter decomposition of the unitary time-evolution operator, when the Trotter step size is chosen to be in the structural instability region, is very different from the target Hamiltonian, which explains the large errors that can occur in the simulation in the regions of instability. These results have implications for the reliability of near-term gate-based quantum simulators, and reveal an important interplay between errors and the physical properties of the system being simulated.

Objective: Many studies have compared outcomes following anterior and posterior cervical fusion, yet the differences in the impacts of perioperative complications on outcomes have not been well studied. This study aimed to assess the differences in the effects of 30-day perioperative complications on patient-reported outcome measures (PROMs) after multilevel anterior versus posterior cervical fusion., Methods: Adult patients who underwent anterior or posterior cervical fusion at three or more levels between 2014 and 2020 were analyzed. Each group was subdivided based on the occurrence and severity of perioperative complication: no complication versus minor complication versus major complication. The study primarily compared PROMs and minimal clinically important differences (MCIDs) within and between the groups., Results: A total of 146 anterior (102 with no complications, 36 with minor complications, 8 with major complications) and 55 posterior (36 with no complications, 13 with minor complications, 6 with major complications) cervical fusion cases were analyzed. Within the anterior or posterior group, there were no significant differences in the PROM change or proportions of patients achieving the MCID. In comparing the anterior group with the posterior group, anterior patients without complications had better improvement in the 3-month Neck Disability Index (coefficient 11.2, p = 0.019), with higher odds of achieving the MCID for the modified Japanese Orthopaedic Association score at 3 months (OR 2.0, p = 0.039). Otherwise, there were no significant differences in the PROM change or proportions of patients achieving the MCID in subsets of anterior or posterior patients with minor or major complications. Furthermore, patients with major complications had higher early readmission rates regardless of the surgical approach. Major complications were also associated with longer and increased rates of intensive care unit stays after posterior fusion compared with anterior fusion., Conclusions: This study suggests that the severity of perioperative complications following anterior or posterior cervical fusion did not predict changes in PROMs or achievement of MCIDs in the anterior or posterior group. Also, PROMs may not fully differentiate the full extent of the impact of perioperative complications following anterior versus posterior cervical fusion. Otherwise, in subsets of patients without complications, anterior compared with posterior patients had improved Neck Disability Index scores at 3 months, with a significant proportion of patients achieving the MCID for the modified Japanese Orthopaedic Association score at 3 months.

Objective: This study evaluates the impact of L4-L5 minimally invasive surgery (MIS)- transforaminal lumbar interbody fusion (TLIF) on adjacent-level parameters., Methods: This is a retrospective study performed on consecutive patients between January 2015 and December 2019. The index- and adjacent-level segmental lordosis (SL) and disc angle (DA) were measured. Patient-reported outcomes (PROs) were collected preoperatively and at 3-24 months postoperatively. Factors influencing changes in adjacent-level parameters and the occurrence of adjacent segment degeneration (ASDeg) were assessed., Results: A total of 117 adult patients, averaging 65.5 years of age and slight preponderance of female (56.4%), were analyzed. L4-L5 SL decreased at 2 years (P < 0.05), but L4-L5 DA significantly increased at all timepoints (P < 0.05). While L3-L4 SL and DA significantly decreased at all timepoints (P < 0.05), L5-S1 SL decreased at 3 and 12 months (P < 0.05) and L5-S1 DA only significantly decreased at 2 years (P < 0.05). All PROs improved significantly (P < 0.0001). The ASDeg rate was 19.7% at 2.2 years. Cephalad and caudal ASDeg rates were 12.0% and 10.3%, respectively. Eight patients (6.8%) required adjacent-level reoperations, mainly at L3-L4 (6 cases). The use of expandable cage significantly reduced the odds of caudal ASDeg (OR 0.15, P = 0.037), but had no significant effect on cephalad ASDeg., Conclusions: L4-L5 MIS-TLIF had a more consistent effect on L3-L4 than L5-S1. Although adjacent-level SL and DA decreased over time, their association with ASDeg appears limited, suggesting a multifactorial etiology. L4-L5 MIS-TLIF provides demonstrable clinical benefits with lasting PRO improvements and low adjacent-level reoperations., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: The comparative effectiveness of decompression plus lumbar facet arthroplasty versus decompression plus instrumented lumbar spinal fusion in patients with lumbar spinal stenosis and grade-I degenerative spondylolisthesis is unknown., Methods: In this randomized, controlled, Food and Drug Administration Investigational Device Exemption trial, we assigned patients who had single-level lumbar spinal stenosis and grade-I degenerative spondylolisthesis to undergo decompression plus lumbar facet arthroplasty (arthroplasty group) or decompression plus fusion (fusion group). The primary outcome was a predetermined composite clinical success score. Secondary outcomes included the Oswestry Disability Index (ODI), visual analog scale (VAS) back and leg pain, Zurich Claudication Questionnaire (ZCQ), Short Form (SF)-12, radiographic parameters, surgical variables, and complications., Results: A total of 321 adult patients were randomized in a 2:1 fashion, with 219 patients assigned to undergo facet arthroplasty and 102 patients assigned to undergo fusion. Of these, 113 patients (51.6%) in the arthroplasty group and 47 (46.1%) in the fusion group who had either reached 24 months of postoperative follow-up or were deemed early clinical failures were included in the primary outcome analysis. The arthroplasty group had a higher proportion of patients who achieved composite clinical success than did the fusion group (73.5% versus 25.5%; p < 0.001), equating to a between-group difference of 47.9% (95% confidence interval, 33.0% to 62.8%). The arthroplasty group outperformed the fusion group in most patient-reported outcome measures (including the ODI, VAS back pain, and all ZCQ component scores) at 24 months postoperatively. There were no significant differences between groups in surgical variables or complications, except that the fusion group had a higher rate of developing symptomatic adjacent segment degeneration., Conclusions: Among patients with lumbar spinal stenosis and grade-I degenerative spondylolisthesis, lumbar facet arthroplasty was associated with a higher rate of composite clinical success than fusion was at 24 months postoperatively., Level of Evidence: Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: This study was funded by Premia Spine (the manufacturer of the device being studied), which funded third-party data management and statistical analysis as well as the study coordinators at the study sites. The Article Processing Charge for open access publication was funded by Premia Spine. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article ( http://links.lww.com/JBJS/H984 )., (Copyright © 2024 The Authors. Published by The Journal of Bone and Joint Surgery, Incorporated.)

Background and Objectives: Studies have demonstrated increased risk of adjacent segment disease (ASD) after open fusion with adjacent-level laminectomy, with rates ranging from 16%-47%, potentially related to disruption of the posterior ligamentous complex. Minimally invasive surgical (MIS) approaches may offer a more durable result. We report institutional outcomes of simultaneous MIS transforaminal lumbar interbody fusion (MISTLIF) and adjacent-level laminectomy for patients with low grade spondylolisthesis and ASD., Methods: Retrospective analysis was performed on patients who underwent MISTLIF with adjacent level laminectomy to treat grade I-II spondylolisthesis with adjacent stenosis at a single institution from 2007-2022., Results: A total of 34 patients met criteria, with mean follow-up of 23.1 months. In total, 37 levels were fused and 45 laminectomies performed. In this group, 21 patients received a single level laminectomy and single-level MISTLIF, 10 patients received a 2-level laminectomy and single-level MISTLIF, 2 patients received a single-level laminectomy and 2-level MISTLIF, and 1 patient received a 2-level laminectomy and 2-level MISTLIF. Three (8.8%) patients experienced clinically significant postoperative ASD requiring reoperation. Three other patients required reoperation for other reasons. Multiple logistic regression did not reveal any association between development of ASD and surgical covariates., Conclusion: MISTLIF with adjacent-level laminectomy demonstrated a favorable safety profile with rates of postoperative ASD lower than published rates after open fusion and on par with the published rates of ASD from MISTLIF alone. Future prospective studies may better elucidate the durability of adjacent-level laminectomies when performed alongside MISTLIF, but retrospective data suggests it is safe and durable., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Narcotic consumption in the workers' compensation population contributes to prolonged case duration, worse clinical outcomes, and opioid dependence. In 2016, the CDC provided recommendations guiding clinicians on prescribing opioids to adult patients with chronic pain. The objective of our study was to evaluate a cause-and-effect relationship between narcotic consumption and worker compensation claim length before and following guideline revision., Methods: An administration database was retrospectively queried to identify patients evaluated for spine-related workers' compensation claimants from 2011 to 2021. Data was recorded for age, sex, BMI, case length, narcotic usage, and injury location. Cases were grouped together by exam date before (2011-2016) and after (2017-2021) the 2016 CDC opioid guideline revision., Results: Six hundred twenty-five patients were evaluated. Males composed 58% of the study population. From 2011 to 2016, narcotic consumption was reported in 54% of subjects versus no narcotic consumption in 46% of subjects (135 cases). From 2017 to 2021, narcotic consumption decreased to 37% (P = 0.00298). Prior to the guideline revision, mean case length was 635 days. Following CDC guideline revision, there was a significant decline in mean case length duration to 438 days (31% reduction) (P = 0.000868)., Conclusion: This study demonstrates that following revised opioid prescription recommendations by the CDC in 2016, there was a statistically significant decline in opioid consumption and workers' compensation case length duration. Opioid use may influence prolonged worker disability and delayed return to work., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background and Objective: This study aimed to evaluate the sleep patterns of students and employees working onsite versus those working from home during the COVID-19 pandemic using actigraphy., Methods: A total of 75 students/employees (onsite: N  = 40, home-office: N  = 35; age range: 19-56 years; 32% male; 42.7% students, 49.3% employees) were studied between December 2020 and January 2022 using actigraphy, a sleep diary, and an online questionnaire assessing sociodemographics and morningness-eveningness. Independent-sample t -tests, paired-sample tests, and a multivariate general linear model adjusting for age (fixed factors: sex and work environment) were applied., Results: Overall, onsite workers had significantly earlier rise times (7:05 [SD: 1:11] versus 7:44 [1:08] hours) and midpoints of sleep (2:57 [0:58] versus 3:33 [0:58] hours) on weekdays compared to home-office workers. Sleep efficiency, sleep duration, variability of sleep timing, and social jetlag did not differ between the groups., Discussion: Home-office workers showed a delay in sleep timing that did not affect any other sleep parameters such as sleep efficiency or nighttime sleep duration. The work environment had only marginal impact on sleep patterns and thus sleep health in this sample. Sleep timing variability did not differ between groups., Supplementary Information: The online version of this article (10.1007/s11818-023-00408-5) contains supplementary material 1 and 2, which is available to authorized users., Competing Interests: Conflict of interestN. Staller, M. Quante, H. Deutsch, and C. Randler declare that they have no competing interests., (© The Author(s) 2023.)

Background: Nonunion remains a concern in multilevel anterior cervical discectomy and fusion (ACDF), yet there are limited data on nonunion after 4 to 5-level ACDF. In fact, the largest series on 4-level or 5-level ACDF focused specifically on the swallowing outcomes., Objective: To assess nonunion after 4 to 5-level ACDF., Methods: Forty-one patients treated with 4 to 5-level ACDF with minimum of 12-month radiographic follow-up were retrospectively reviewed. Nonunion was found in 25 patients (61%) and 42 levels (25%) and complete fusion in 16 (39%) patients and 126 levels (75%). The 2 groups were further compared., Results: One-level nonunion was by far the most common pattern compared with multilevel nonunion. Nonunion occurred more frequently at the caudal than the cranial or middle segments ( P < .0001). There were significantly more subsidence ( P < .0001) and screw fractures/pullouts ( P < .0001) in the nonunion compared with the fusion group. The symptomatic patients were significantly younger than the asymptomatic patients ( P = .044). The symptomatic levels were significantly more than asymptomatic levels ( P = .048). Equal proportion of patients implanted with allograft and polyetheretherketone had nonunion. However, there were markedly more nonunion than fused levels with allograft and more fused than nonunion levels with polyetheretherketone ( P = .023). The reoperation rate was 24.4% and mostly due to nonunion. There were no reoperations within 90 days of the primary surgery., Conclusion: The nonunion rate for 4-level and 5-level ACDF may be higher than previously reported. Symptomatic nonunion remains a major reason for reoperation after multilevel ACDF. Baseline characteristics that negatively affect fusion may be obviated by careful patient selection., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Objective: This study assesses cervical alignments after 2-level cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) with anterior plate fixation., Methods: Eighty-two patients who underwent 2-level CDA or ACDF in 2014-2019 were identified. Cervical alignment parameters were compared between the 2 cohorts. Subgroup analyses were performed to determine factors that differentiate alignment outcomes between the 2 procedures., Results: Although both cohorts achieved significant focal lordosis (FL) and overall cervical lordotic (CL) gains, CDA cohorts achieved significantly greater 12-month FL gain (P = 0.022). However, in a multivariate analysis controlling for preoperative variables, FL gain was no longer significant. Although the CDA cervical sagittal vertical axis (cSVA) significantly improved at 3 (P = 0.030) and 12 (P = 0.007) months, these improvements were not superior to the ACDF cSVA. Male patients undergoing CDA achieved greater 12-month CL gain. Patients undergoing CDA with body mass index >25 kg/m 2 achieved greater 12-month FL gain. Patients undergoing CDA with symptom duration >12 months achieved greater FL gain at 3 and 12 months. Patients undergoing CDA with high baseline T1 slope or cSVA achieved greater 12-month cSVA reduction. Clinical outcomes were comparable between the 2 cohorts. Unlike the ACDF group, CL gain in the CDA group was significantly correlated with the cSVA reduction, which was associated with significant improvement in the Neck Disability Index, arm pain, and 12-Item Short-Form Mental Component Scores. Heterotopic ossification was not found to significantly affect patient outcome and cervical alignment in both cohorts., Conclusions: ACDF and CDA are viable options for 2-level degenerative disc disease in carefully selected patients. Both approaches produced equivalent postoperative alignment changes in a 2-level operation., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objective: There are limited patient-reported outcome measure (PROM) data on 4-level and 5-level anterior cervical discectomy and fusion (ACDF). The largest series to date solely focused on complications. This retrospective series evaluates PROMs after 4-level and 5-level ACDF., Methods: Pertinent data from adult patients treated with a 4-level or 5-level ACDF in 2011-2019 were analyzed. PROMs and minimal clinically important differences (MCIDs) were assessed. Factors associated with favorable and unfavorable outcomes were identified., Results: There were 34 patients (30 underwent 4-level and 4 underwent 5-level ACDFs) with a mean age of 59.6 years; 55.9% were women. At 3 months, there were significant improvements in PROMs except Short-Form 12-Item Survey (SF-12) mental component subscale, which showed modest improvement. At 12 months, there were significant improvements in PROMs except SF-12 physical component subscale (PCS), which showed moderate improvement. The proportions of patients who met the MCID cutoffs ranged from 35.3% (numeric rating scale [NRS]-neck) to 75% (Veteran RAND 12-Item Survey [VR-12] PCS) at 3 months and 38.2% (NRS-arm) to 65.5% (VR-12 mental component subscale) at 12 months. Shorter symptom duration was associated with significantly reduced postoperative pain and Neck Disability Index scores. Shorter length of stay was associated with significantly improved postoperative functional outcomes. patients undergoing 4-level compared with 5-level ACDF achieved better postoperative PROMs. Shorter procedure duration was associated with improved PROMs at 3 months. No patient returned to the operating room within 30 days. Patients who required reoperation achieved significantly inferior Neck Disability Index, NRS-neck, and SF-12 PCS scores at 3 months., Conclusions: This study showed satisfactory PROMs up to 12 months after 4-level and 5-level ACDF despite the complication rate. With thorough preoperative planning and meticulous technique, performing this procedure in carefully selected patients may be associated with acceptable PROMs., (Copyright © 2022 Elsevier Inc. All rights reserved.)