Hamiltonian Engineering with Multicolor Drives for Fast Entangling Gates and Quantum Crosstalk Cancellation

Quantum computers built with superconducting artificial atoms already stretch the limits of their classical counterparts. While the lowest energy states of these artificial atoms serve as the qubit basis, the higher levels are responsible for both a host of attractive gate schemes as well as generating undesired interactions. In particular, when coupling these atoms to generate entanglement, the higher levels cause shifts in the computational levels that lead to unwanted ZZ quantum crosstalk. Here, we present a novel technique to manipulate the energy levels and mitigate this crosstalk with simultaneous off-resonant drives on coupled qubits. This breaks a fundamental deadlock between qubit-qubit coupling and crosstalk. In a fixed-frequency transmon architecture with strong coupling and crosstalk cancellation, additional cross-resonance drives enable a 90 ns CNOT with a gate error of (0.19±0.02)%, while a second set of off-resonant drives enables a novel CZ gate. Furthermore, we show a definitive improvement in circuit performance with crosstalk cancellation over seven qubits, demonstrating the scalability of the technique. This Letter paves the way for superconducting hardware with faster gates and greatly improved multiqubit circuit fidelities.

Performance evaluation of various aerobic biological systems for the treatment of domestic wastewater at low temperatures

Studies were undertaken on the performance evaluation of three different types of aerobic reactors, namely, activated sludge process, fluidized bed reactor and submerged bed reactor. Initially synthetic wastewater was used for stabilizing the system and later domestic wastewater of IIT Madras was used as the feed for the biological systems. The hydraulic retention time was maintained as 24 h. The seed sludge was collected from IIT Madras sewage treatment plant. The inlet COD to the reactors with synthetic wastewater was 1,000 +/- 20 mg/L and with real wastewater, it was 150 to 350 mg/L. The performance of the reactors was evaluated based on the soluble COD and nitrogen removal efficiency. The pH, temperature, dissolved oxygen (DO) and mixed liquid suspended solid (MLSS) concentration were measured periodically. The reactors were acclimatized at 35 degrees C in batch mode and changed to continuous mode at 30 degrees C. After the systems attained its steady state at a particular temperature, the temperature was reduced from 35 degrees C to 5 degrees C stepwise, with each step of 5 degrees C. The start-up time for submerged bed reactor was slightly more than fluidized and conventional activated sludge process.The COD removal efficiency of the three reactors was higher with synthetic wastewaters as compared to actual domestic wastewater. Submerged bed reactor was more robust and efficient as compared to activated sludge and fluidized bed reactors. The COD removal efficiency of the reactors was relatively good until the operating temperature was maintained at 15 degrees C or above. At 10 degrees C, submerged bed reactor was able to achieve 40% COD removal efficiency whereas; the fluidized bed and conventional ASP reactors were showing only 20% COD removal efficiency. At 5 degrees C, almost all the systems failed. Submerged bed reactor showed around 20% COD removal efficiency. However, this reactor was able to regain its 90% of original efficiency, once the temperature was raised to 10 degrees C. At higher temperatures, the nitrification efficiency of the reactors was above 80-90%. As the temperature reduced the nitrification efficiency has reduced drastically. In summary, submerged bed reactors seems to be a better option for treating domestic wastewaters at low temperature regions.

Management of tumors of the thoracolumbar spine

Current improvements in radiologic imaging and surgical instrumentation have greatly expanded the role of surgery in management of tumors of the thoracolumbar junction. For primary malignant tumors, the aim of surgery should be curative, with eradiction of all gross disease. For metastatic tumors, indications for surgery include cancer therapy, stabilization, neurologic palliation, tissue diagnosis, and pain relief. Because the thoracolumbar region is a transitional zone, surgical stabilization may require anterior-posterior approaches and instrumentation.

Indications and results of combined anterior-posterior approaches for spine tumor surgery

Spinal instrumentation currently allows gross-total resection and reconstruction in cases of malignancies at all levels of the spine. The authors analyzed the results in 110 patients who underwent surgery for primary and metastatic spinal tumors over a 5-year period (1989-1993) at a single institution. Major primary sites of tumor included breast (14 cases), chordoma (14 cases), lung (12 cases), kidney (11 cases), sarcoma (13 cases), plasmacytoma (10 cases), and others (36 cases). Prior to surgery, 55 patients (50%) had received prior treatment. Forty-eight patients (44%) were nonambulatory, and severe paraparesis was present in 20 patients. Fifty-three patients (48%) underwent combined anterior-posterior resection and instrumentation. 33 (30%) underwent anterior resection with instrumentation, 18 (16%) underwent anterior or posterior resection alone, and the remaining six patients (5%) underwent posterior resection and instrumentation. Major indications for anterior-posterior resection included three-column involvement, high-grade instability, involvement of contiguous vertebral bodies, and solitary metastases. Postoperatively, 90 patients improved neurologically. The overall median survival was 16 months, with 46% of patients surviving 2 years. Fifty-three patients (48%) suffered postoperative complications. Despite the high incidence of complications, the majority of patients reported improvement in their quality of life at follow-up review. Our findings suggest that half of all patients with spinal malignancies require combined anterior-posterior surgery for adequate tumor removal and stabilization.

Surgical treatment of spinal cord compression from epidural metastasis

PURPOSE

A retrospective study of the results of neoplastic cord compression was undertaken to determine the effectiveness of surgical treatment and to assess quality of life in patients undergoing extensive procedures with potential morbidity.

PATIENTS AND METHODS

Over a 5-year period (1989 to 1993), a total of 110 patients underwent surgery. Fifty-five patients (50%) had undergone prior treatment, including 47 (43%) who had failed to respond to prior irradiation (RT). Before surgery, 48 patients (44%) were nonambulatory, with severe paresis being present in 20. Surgery included staged anterior-posterior resections in 53 patients (48%), anterior resections in 33 (30%), and posterior resection in six (5%), all of whom required spinal instrumentation for reconstruction; only 18 patients underwent resection without instrumentation.

RESULTS

Postoperatively, 90 patients (82%) were improved, both in terms of pain relief and ambulatory status. Fifty-three patients (48%) experienced postoperative complications, related statistically to the following three factors: age over 65 years, prior treatment, and presence of paraparesis. The overall median survival duration was 16 months, with 46% alive at 2 years. Apart from primary tumor, the presence of preoperative paraparesis had the most significant impact on survival.

CONCLUSION

Our data suggest that the effective surgical treatment of neoplastic compression requires anterior-posterior resection in most patients to achieve the goal of total tumor resection, with the majority requiring instrumentation. Long-term survival is feasible in a subset of patients with this aggressive surgical approach.

Management of the vertebral artery in excision of extradural tumors of the cervical spine

Extradural tumors of the cervical spine may involve the vertebral artery on one or both sides, posing one of the limiting factors toward the radical resection of such neoplasms. A standard anterior approach may be inadequate for the management of such tumors. An anterolateral approach allows the dissection and mobilization of the vessel, which can then be preserved, resected, or reconstructed with a vein graft. An anterior approach can be supplemented with this for tumor resection and stabilization. This management strategy is described in 10 patients with a variety of tumors.

Use of instrumentation in degenerative disease of the cervical spine

Degenerative diseases of the cervical spine (including cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament) occur predominantly in elderly persons. Decompressive laminectomy has been the standard of surgical treatment in the United States for several decades. Postlaminectomy kyphosis and instability and inadequate decompression of anterior compressing forces can fail to halt and may even contribute to progression of neurologic deterioration. Instrumentation of the cervical spine provides a means of stabilization and allows safer multilevel anterior decompression. The biomechanics of degenerative disease of the cervical spine as well as surgical treatment options are discussed. Atlantoaxial transarticular screw fixation and other modalities of instrumentation are described.

Pediatric spinal axis tumors

Pediatric spinal cord tumors occur in the intramedullary or extramedullary spaces. The extramedullary tumors are further divided into those in intradural-extramedullary or extradural locations. Tumors in the intradural-extramedullary region include nerve sheath tumors, meningiomas, and "embryonal" tumors. In the extradural space are neuroblastomas, sarcomas, and other primary tumors of bone. The radiographic findings, histology, and management of each type of tumor are included in this article, which focuses on extramedullary tumors.

Treatment of neoplastic spinal cord compression: results of a prospective study

Currently, external radiation and steroid therapy are used in most patients with neoplastic spinal cord compression. Surgery is generally used to treat those who do not respond to radiation therapy. To determine the role of de novo surgery in patients with spinal metastases, a prospective study was undertaken. Over a 4 1/2-year period, the cases of 54 patients with radiologically documented spinal metastases were studied. The sites of tumor origin included soft tissue sarcoma (8 patients), kidney (6 patients), lung (5 patients), breast (5 patients), spine (6 patients), unknown primary site (6 patients), and others (18 patients). Sites of compression included the cervical spine segments in 15 patients, thoracic segments in 23, lumbar in 14, and sacral in 2. Before surgery, 24 patients (44%) were nonambulatory. Three surgical approaches were used: anterior vertebral body resection in 45 patients, laminectomy in 7, and lateral osteotomy in 2. After surgery, 37 patients received external radiation therapy. All patients improved (became ambulatory) after surgery, with 23 of 25 patients surviving at 2 years continuing to be ambulatory. The 30-day mortality rate was 6% (three patients); eight patients (15%) sustained various surgical complications. These results are superior to those reported after external radiation therapy and steroids alone, and they support the concept that de novo surgery be considered in selected patients with spinal metastases.

Spinal instrumentation for degenerative disease of the lumbar spine

Instrumentation for spinal implant is currently changing more rapidly than at any previous period in its 100-year history. At present, the most common indication for spinal instrumentation is degenerative disease of the lumbar spine, which can be roughly categorized as of three kinds: herniated lumbar disks, spondylolisthesis, and spinal stenosis. The literature on indications for arthrodesis is reviewed. A brief summary of the approach and type of instrumentation available for the lumbar spine is presented.

Treatment of spinal metastases from kidney cancer by presurgical embolization and resection

Surgical treatment of bone metastases from kidney cancer is often complicated by profuse blood loss. The authors report the results of a retrospective review of 30 consecutive patients who underwent surgery for spinal metastases from kidney cancer. Seventeen patients (57%) were operated on after failing radiation therapy. Prior to operation, selective spinal angiography and embolization were performed in 17 patients with no permanent neurological deficits resulting. Gross total resection of the tumor and stabilization of the spine were then accomplished with acceptable blood loss. Twenty-seven (90%) of the 30 patients improved neurologically following surgery. There was a median survival time of 16 months, a 2-year survival rate of 33%, and a 5-year survival rate of 15%. Major surgical complications in this series were related to excessive blood loss in patients without embolization. These data suggest that patients with spinal metastases from kidney cancer should undergo spinal angiography and embolization prior to resection of the tumor. To improve upon current results, such treatment should be carried out prior to external radiation therapy.

Chemotherapy of recurrent esthesioneuroblastoma. Case report and review of the literature

Esthesioneuroblastoma is a rare epithelial tumor of the nasal olfactory mucosa. Its clinical course is characterized by indolent growth and persistent local recurrence and occasional distant metastases despite attempts at cure. Our report documents the response of a patient to a cisplatin-based drug combination and reviews the English-language literature of 25 patients treated with chemotherapy. We conclude that this tumor is sensitive to several different combinations and suggest guidelines for the use of chemotherapy in advanced or metastatic esthesioneuroblastoma.

Optimal use of the Ommaya reservoir in clinical oncology

A major obstacle to the effective systemic therapy of intracranial malignancies and infections, the bloodbrain barrier was overcome by the development of the Ommaya reservoir in 1963. Initially used in treating cryptococcal meningitis, this closed system for continued access to the ventricular spaces has a variety of applications. They include treatment of cancer pain, chronic or recurrent CNS infection, prophylaxis of CNS involvement in acute lymphoblastic leukemia, and treatment of leptomeningeal malignancy. The authors outline the rationale, latest indications, surgical technique, and potential complications arising from the use of the Ommaya reservoir and other such subcutaneous reservoirs.

Spondylectomy for malignant tumors of the spine

Spondylectomy is the complete surgical removal of all parts of one or more vertebrae above the sacrum. We report our initial experience with spondylectomy in eight patients with malignant tumors of the spine operated on over a 7-year period (1980 to 1986). Four patients had primary neoplasms of the spine, and four others had solitary metastases to the vertebrae. Following surgery, five patients underwent radiation therapy (RT) and chemotherapy depending on histology of the tumor. Radiographic confirmation of tumor resection was obtained on all patients. Pain relief was noted in all patients, and six patients with preoperative neurological deficits improved. There was no surgical mortality, and one patient developed wound dehiscence following surgery. Six of the eight patients are alive with a median follow-up of 36 months, and local control was achieved in six of the eight patients. These preliminary data suggest that malignant tumors of the spine can be completely resected using a staged approach. In potentially responsive tumors, systemic chemotherapy is recommended between the two operations to reduce the risk of systemic dissemination.

Neurosurgery in the treatment of cancer pain

Patients with pain syndromes resulting from recurrent or metastatic cancer should be evaluated carefully to determine the cause of their pain and the need for appropriate antitumor treatment. Currently, opioid analgesics are the mainstay of pain control, but side effects limit their use in some patients. When pharmacologic pain control is inadequate or associated with intolerable side effects, neurosurgery should be considered. Currently the implantation of a pump for the intraspinal infusion of opioid analgesics is the most popular procedure, but its usefulness may be limited by the development of opioid tolerance. The most effective ablative pain control procedure at the current time is cordotomy, which is indicated in patients with unilateral pain. Although the place of neurostimulatory procedures in controlling cancer pain is not well established, they are attractive because of their nondestructive nature and potential usefulness in the treatment of bilateral pain syndromes. Specific antitumor surgical procedures should be considered in patients with certain spinal and plexopathy syndromes, because such intervention offers the prospect of both pain relief and tumor control. In this article, the neurosurgical procedures used in the management of cancer pain are reviewed.

Combined treatment of osteosarcoma of the spine

We reviewed the clinical features and results of treatment in 24 patients with osteogenic sarcoma of the spine treated over a 35-year period. There were 14 male and 10 female patients 13 to 71 years old. The tumor arose de novo in 13 patients and was secondary to other conditions in 11. All patients presented with pain, and 16 (67%) had neurological deficits. Patients were divided into two treatment groups. Thirteen patients treated from 1949 to 1977 usually underwent limited tumor resection and external radiation therapy. The second group, 11 patients treated from 1978 to 1984, underwent more aggressive surgical resection and received combination chemotherapy as well as local radiation to the tumor bed. In the second group, there were 5 long term survivors, and only 1 patient developed metastatic disease while on therapy. Failure to obtain local control was the major cause of treatment failure. Complete surgical resection of the tumor by spondylectomy and combination chemotherapy offer the best prospect for cure of osteogenic sarcoma of the spine.

Reoperation for brain metastases

We report the results of reoperation for brain metastases in 21 patients with recurrent tumors following initial successful resection. The tumor recurrences were local (original site) in 14 patients, and occurred at other sites in the brain in the remaining seven. Time to CNS recurrence ranged from 3 to 30 months. At time of repeat craniotomy, disease was limited to the CNS in 12 (57%) of the patients. Median survival following second craniotomy was 9 months, and the actuarial 2-year survival was 25%. Neurological improvement was seen in two thirds of the patients; the median duration of neurological improvement was 6 months. There was no mortality, and only one patient developed increased deficit following surgery. We conclude that repeat resection of brain metastases is an important therapeutic option in selected patients, and should be considered in symptomatic patients with accessible mass lesions before the use of other experimental treatment.

Craniofacial resection for anterior skull base tumors

We present the results of treatment of 30 patients with anterior skull base tumors operated on over an 11-year period. At the time of surgery, intracranial invasion was present in 10 patients. Histology revealed epithelial tumors in 18 patients, sarcoma in 6, esthesioneuroblastoma in 4, and 2 miscellaneous histologies. The overall median survival was 5 years and varied according to histology and grade of tumor. Currently malignancies involving the skull base can be successfully resected using a craniofacial approach, with minimum operative mortality. Limited intracranial invasion need not necessarily represent a major contraindication of this procedure if morbidity can be kept to a minimum.

Surgical treatment of spinal chordomas

The clinical features and results of 34 patients with chordomas treated over a seven-year period were analyzed. Surgical treatment consisted of wide local excision (n = 6), marginal resection (n = 5), intralesional resection (n = 20), and biopsy (n = 3). Eighteen patients received postoperative radiotherapy. The local recurrence rate was 65%, with 30% of patients developing distant metastases. With the introduction of computed tomography, smaller tumors are currently being diagnosed; as a result, 35% of the patients in this series are disease free, compared with 10% described previously.

The combined neurosurgical-thoracic management of superior sulcus tumors

Thirty patients with superior sulcus carcinoma were prospectively evaluated over an 18-month period. All patients underwent complete neuroradiological evaluation by computed tomography (CT) and myelography. Prior to operation, brachial plexopathy was noted in 20 patients (67%), and invasion of the spine in eight (27%). Using a team approach, gross total resection of tumor was achieved in 17 of 26 patients (65%) undergoing thoracotomy. There was no operative mortality. The use of a team approach allows extended surgical resection, especially when the spine is involved. In patients presenting with brachial plexopathy or cord compression, de novo surgery before radiation may provide better long-term palliation and pain relief.