Simulating Lattice Gauge Theories within Quantum Technologies

Lattice gauge theories, which originated from particle physics in the context of Quantum Chromodynamics (QCD), provide an important intellectual stimulus to further develop quantum information technologies. While one long-term goal is the reliable quantum simulation of currently intractable aspects of QCD itself, lattice gauge theories also play an important role in condensed matter physics and in quantum information science. In this way, lattice gauge theories provide both motivation and a framework for interdisciplinary research towards the development of special purpose digital and analog quantum simulators, and ultimately of scalable universal quantum computers. In this manuscript, recent results and new tools from a quantum science approach to study lattice gauge theories are reviewed. Two new complementary approaches are discussed: first, tensor network methods are presented - a classical simulation approach -applied to the study of lattice gauge theories together with some results on Abelian and non-Abelian lattice gauge theories. Then, recent proposals for the implementation of lattice gauge theory quantum simulators in different quantum hardware are reported, e.g., trapped ions, Rydberg atoms, and superconducting circuits. Finally, the first proof-of-principle trapped ions experimental quantum simulations of the Schwinger model are reviewed

Lumbar spondylolysis: a life long dynamic condition? A cross sectional survey of 4.151 adults

Lumbar spondylolysis (LS) has been the subject of several studies focusing on adolescent athletes. Few, if any, studies have examined LS in the general population. Lysis of the pars interarticularis of the vertebra may be associated with slipping (olisthesis), or it may be stable. In the present survey of lumbar radiographs and general epidemiological data recorded from the Copenhagen Osteoarthritis Study cohort of 4.151 subjects (age range, 22–93 years), we identified the distribution and individual risk factors for LS-development. Men were significantly more at risk of L5 spondylolysis (P = 0.002). There were no sex-specific significant differences regarding LS-incidence at the L4 level. We found no significant differences of risk of LS between nulliparous or multiparous women (L4 P = 0.54/L5 P = 0.35). Furthermore, we found no significant relationship between age at menopause and LS-development. Increased lumbar lordosis was associated to L4/L5 spondylolysis in men (L4 P < 0.001/L5 P = 0.008). In women increased lumbar lordosis had a significant association with L5 spondylolysis (P < 0.001). Increased pelvic inclination was associated with L5 spondylolysis in both men and women (P < 0.001). There were no sex-specific differences regarding the occurrence of simultaneous slips/non-slips. In men, no individual risk factors for L4 slips with concomitant LS were found. In women slipped LS of L4 were significantly associated to aging (P < 0.001) and with decreased pelvic inclination (P = 0.001). In men slipped LS of L5 was significantly associated to increased BMI (P = 0.002), but not to aging (P = 0.10). In women, slips of L5 LS were significantly correlated to aging (P = 0.005), to BMI recorded at the time of radiographic examination (P = 0.006), and BMI measured 17 years before radiographic index examination (P = 0.004). The present study contrasts with commonly held views regarding lumbar spondylolysis. The prevalence of LS increases throughout life and is apparently not a condition restricted to adolescence. Although the cross-sectional nature of the present study prevents an exact estimate of the age at onset; future, sequential studies of the cohort may provide us with some important answers on this topic. Apart from aging–obesity, lordotic angle and pelvic inclination were found to be individual risk factors for LS

A level-1 pilot study to evaluate of ultraporous β-tricalcium phosphate as a graft extender in the posterior correction of adolescent idiopathic scoliosis

The objective of this study is to compare the clinical and radiographic results of ultraporous β-tricalcium phosphate (β-TCP) versus autogenous iliac crest bone graft (ICBG), through prospective randomized pilot study (EBM-Level 1), as graft extenders in scoliosis surgery. In the posterior correction of scoliosis, local bone resected as part of the procedure is used as the base bone graft material. Supplemental grafting from the iliac crest is considered the gold-standard in posterior spinal fusion. However, autograft is not available in unlimited quantities, and bone harvesting is a source of significant morbidity. Ultraporous β-TCP might be a substitute for ICBG in these patients and thus eliminate donor site morbidity. A total of 40 patients with adolescent idiopathic scoliosis (AIS) were randomized into two treatment groups and underwent corrective posterior instrumentation. In 20 patients, ICBG harvesting was performed whereas the other half received β-TCP (VITOSS®) to augment the local bone graft. If thoracoplasty was performed, the resected rib bone was added in both groups. Patients were observed clinically and radiographically for a minimum of 20 months postoperatively, with a mean follow-up of 4 years. Overall pain and pain specific to the back and donor site were assessed using a visual analog scale (VAS). As a result, both groups were comparable with respect to the age at the time of surgery, gender ratio, preoperative deformity, and hence length of instrumentation. There was no significant difference in blood loss and operative time. In nine patients of the β-TCP group and eight patients of the ICBG group, thoracoplasty was performed resulting in a rib graft of on average 7.9 g in both groups. Average curve correction was 61.7% in the β-TCP group and 61.2% in the ICBG group at hospital discharge (P = 0.313) and 57.2 and 54.3%, respectively, at follow-up (P = 0.109). Loss of curve correction amounted on average 2.6° in the β-TCP group and 4.2° in the comparison group (P = 0.033). In the ICBG group, four patients still reported donor site pain of on average 2/10 on the VAS at last follow-up. One patient in the β-TCP group was diagnosed with a pseudarthrosis at the caudal end of the instrumentation. Revision surgery demonstrated solid bone formation directly above the pseudarthrosis with no histological evidence of β-TCP in the biopsy taken. In conclusion, the use of β-TCP instead of ICBG as extenders of local bone graft yielded equivalent results in the posterior correction of AIS. The promising early results of this pilot study support that β-TCP appears to be an effective bone substitute in scoliosis surgery avoiding harvesting of pelvic bone and the associated morbidity