High-fidelity spin qubit operation and algorithmic initialization above 1 K.

The encoding of qubits in semiconductor spin carriers has been recognized as a promising approach to a commercial quantum computer that can be lithographically produced and integrated at scale1-10. However, the operation of the large number of qubits required for advantageous quantum applications11-13 will produce a thermal load exceeding the available cooling power of cryostats at millikelvin temperatures. As the scale-up accelerates, it becomes imperative to establish fault-tolerant operation above 1 K, at which the cooling power is orders of magnitude higher14-18. Here we tune up and operate spin qubits in silicon above 1 K, with fidelities in the range required for fault-tolerant operations at these temperatures19-21. We design an algorithmic initialization protocol to prepare a pure two-qubit state even when the thermal energy is substantially above the qubit energies and incorporate radiofrequency readout to achieve fidelities up to 99.34% for both readout and initialization. We also demonstrate single-qubit Clifford gate fidelities up to 99.85% and a two-qubit gate fidelity of 98.92%. These advances overcome the fundamental limitation that the thermal energy must be well below the qubit energies for the high-fidelity operation to be possible, surmounting a main obstacle in the pathway to scalable and fault-tolerant quantum computation.

Simultaneous Robotic-Assisted Bilateral Native Nephrectomy and Kidney Transplantation for Autosomal Dominant Polycystic Kidney Disease in Recipients With High Body Mass Index: Report of 2 Cases.

Robotic kidney transplantation is a safe, reproducible, and less morbid technique in high body mass index and end-stage renal disease. Polycystic kidney disease is a relative contraindication to robotic-assisted kidney transplantation because of the mass effect of the native kidneys on the patient's pelvis that prevents ideal exposure. We report the first 2 cases of robotic-assisted simultaneous bilateral nephrectomy and kidney transplantation for patients with obesity and adult polycystic kidney disease. The recipients were 2 males, 50 and 53 years old, with a body mass index of 35.1 41.6 kg/m2 and 41.6 kg/m2, respectively. Both recipients had suitable living donors. The average operating time was 395 minutes and the estimated blood loss was on average 250 mL. The postoperative course was uneventful and the patients were discharged home on days 4 and 5. Performing robotic nephrectomies simultaneously with kidney transplantation can be done safely, allowing patients with obesity and polycystic kidney disease needing bilateral nephrectomy, to take full advantage of minimally invasive kidney transplantation.

Low-overhead fault-tolerant quantum computing using long-range connectivity.

Vast numbers of qubits will be needed for large-scale quantum computing because of the overheads associated with error correction. We present a scheme for low-overhead fault-tolerant quantum computation based on quantum low-density parity-check (LDPC) codes, where long-range interactions enable many logical qubits to be encoded with a modest number of physical qubits. In our approach, logic gates operate via logical Pauli measurements that preserve both the protection of the LDPC codes and the low overheads in terms of the required number of additional qubits. Compared with surface codes with the same code distance, we estimate order-of-magnitude improvements in the overheads for processing around 100 logical qubits using this approach. Given the high thresholds demonstrated by LDPC codes, our estimates suggest that fault-tolerant quantum computation at this scale may be achievable with a few thousand physical qubits at comparable error rates to what is needed for current approaches.

Programming a quantum phase of matter.

The ability to measure long-range entanglement may enable robust quantum memory.

A Call for Better, Not Faster, Research Ethics Committee Reviews in the Covid-19 Era.

With the rapid spread of SARS-CoV2 has come a rapid proliferation of clinical research studies, resulting in considerable strain on research ethics committees (RECS), which need to review study proposals. RECs are pressured to move through the review process quickly so that studies can get underway to address the pandemic. These committees are also asked to increase efficiency without relaxing the standards for ethical review. RECs are accustomed to external pressure for approval from investigators; however, in the Covid-19 era, this pressure is coming from not only the sponsors and investigators but also many other stakeholders, including world leaders, the community, the media, and professional organizations. Drawing on the authors' experiences on a central REC reviewing complex multicenter Covid-19 studies, this commentary describes challenges that are inherent to Covid-19 research studies, such as the difficulty of obtaining informed consent from patients ill with the highly infectious virus. The commentary recommends several steps that RECs can take to ensure ethical review of research studies during the Covid-19 pandemic and future infectious disease outbreaks.

First World Consensus Conference on pancreas transplantation: Part II - recommendations.

The First World Consensus Conference on Pancreas Transplantation provided 49 jury deliberations regarding the impact of pancreas transplantation on the treatment of diabetic patients, and 110 experts' recommendations for the practice of pancreas transplantation. The main message from this consensus conference is that both simultaneous pancreas-kidney transplantation (SPK) and pancreas transplantation alone can improve long-term patient survival, and all types of pancreas transplantation dramatically improve the quality of life of recipients. Pancreas transplantation may also improve the course of chronic complications of diabetes, depending on their severity. Therefore, the advantages of pancreas transplantation appear to clearly surpass potential disadvantages. Pancreas after kidney transplantation increases the risk of mortality only in the early period after transplantation, but is associated with improved life expectancy thereafter. Additionally, preemptive SPK, when compared to SPK performed in patients undergoing dialysis, appears to be associated with improved outcomes. Time on dialysis has negative prognostic implications in SPK recipients. Increased long-term survival, improvement in the course of diabetic complications, and amelioration of quality of life justify preferential allocation of kidney grafts to SPK recipients. Audience discussions and live voting are available online at the following URL address: http://mediaeventi.unipi.it/category/1st-world-consensus-conference-of-pancreas-transplantation/246.

The XZZX surface code.

Performing large calculations with a quantum computer will likely require a fault-tolerant architecture based on quantum error-correcting codes. The challenge is to design practical quantum error-correcting codes that perform well against realistic noise using modest resources. Here we show that a variant of the surface code-the XZZX code-offers remarkable performance for fault-tolerant quantum computation. The error threshold of this code matches what can be achieved with random codes (hashing) for every single-qubit Pauli noise channel; it is the first explicit code shown to have this universal property. We present numerical evidence that the threshold even exceeds this hashing bound for an experimentally relevant range of noise parameters. Focusing on the common situation where qubit dephasing is the dominant noise, we show that this code has a practical, high-performance decoder and surpasses all previously known thresholds in the realistic setting where syndrome measurements are unreliable. We go on to demonstrate the favourable sub-threshold resource scaling that can be obtained by specialising a code to exploit structure in the noise. We show that it is possible to maintain all of these advantages when we perform fault-tolerant quantum computation.

Fault-Tolerant Thresholds for the Surface Code in Excess of 5% under Biased Noise.

Noise in quantum computing is countered with quantum error correction. Achieving optimal performance will require tailoring codes and decoding algorithms to account for features of realistic noise, such as the common situation where the noise is biased towards dephasing. Here we introduce an efficient high-threshold decoder for a noise-tailored surface code based on minimum-weight perfect matching. The decoder exploits the symmetries of its syndrome under the action of biased noise and generalizes to the fault-tolerant regime where measurements are unreliable. Using this decoder, we obtain fault-tolerant thresholds in excess of 6% for a phenomenological noise model in the limit where dephasing dominates. These gains persist even for modest noise biases: we find a threshold of ∼5% in an experimentally relevant regime where dephasing errors occur at a rate 100 times greater than bit-flip errors.

A Multidisciplinary Technique for Concurrent Panniculectomy-Living Donor Renal Transplantation.

BACKGROUND: Recently, it has been shown that panniculectomy concurrent to living donor renal transplantation is a safe option for management of renal transplant recipients with a large focal pannus. This combined management requires precise coordination of teams. We describe the technique, timing, and sequence for combined renal transplantation and panniculectomy. METHODS: We conducted a retrospective chart review of adult patients (≥18 years old) who underwent simultaneous living donor renal transplantation-panniculectomy from 2015 to 2019. A multi-team approach that included urology, transplant, and plastic surgery was used to perform the combined operations. Typically, the plastic surgery team initiates the operation by performing the panniculectomy. This is followed by kidney transplantation and graft anastomosis. The plastic surgery team then completes the operation with closure of the wound. RESULTS: Twenty patients were identified. Most were male (12:8) with a mean age of 55 years and an average body mass index of 35 kg/m. The mean total operative duration was 394 minutes. On average, 17% of operating time was devoted to panniculectomy. At 90 days follow-up, there was 100% graft survival and all patients had primary graft function. There was a 25% wound complications rate and a 15% reoperation rate. CONCLUSION: By performing panniculectomy first in the sequence, concurrent panniculectomy provides wide exposure and a large operative field for transplantation. Wound closure by plastic surgeons may mitigate the high complication rate commonly seen in obese patients with end-stage renal disease. Future studies are needed to evaluate the cost-benefit of the combined living donor renal transplantation-panniculectomy.

Teamwork Makes the Dream Work: Maximizing Surgical Intervention at the Time of Living Donor Renal Transplantation.

BACKGROUND: Patients with obesity and end-stage renal disease represent a surgical population with multiple comorbidities and high risk for postoperative complications. One method for reducing the incidence of postoperative adverse events in this patient population is to limit the number of operations through combining operations into 1 operative encounter. METHODS: We conducted a retrospective review of adult patients at a single institution who underwent renal transplant, panniculectomy, and at least 1 additional abdominal or pelvic surgery concurrently. For those patients, we collected demographics, intraoperative variables, and postoperative data and analyzed surgical outcomes and postoperative complications. RESULTS: Thirteen patients met inclusion criteria. Most of the patients were female (85%) with ages ranging 33 to 70 years old and mean body mass index of 36.5 (SD 4.7). Three quarters of patients (77%) underwent 3 procedures and the remaining underwent 4 or 5 procedures with a median hospital length of stay of 5 days (range, 3-10 days). There was a single mortality. Overall, 8 patients (61.5%) experienced complications in the first 90 postoperative days. The wound complication rate was 46.2%, the overall readmission rate within 90 days was 38.5%, and the reoperation rate was 30.8%. All patients experienced immediate graft function, and the 12 patients that survived to postoperative day 90 maintained survival at 1 year. CONCLUSION: This study demonstrates that the combination of more than 2 surgical procedures with living donor renal transplant is a possible treatment option in high-risk obese patients in need of multiple operations.

Early Experience With Preclinical Perioperative Cardiac Xenograft Dysfunction in a Single Program.

BACKGROUND: Perioperative cardiac xenograft dysfunction (PCXD) was described by McGregor and colleagues as a major barrier to the translation of heterotopic cardiac xenotransplantation into the orthotopic position. It is characterized by graft dysfunction in the absence of rejection within 24 to 48 hours of transplantation. We describe our experience with PCXD at a single program. METHODS: Orthotopic transplantation of genetically engineered pig hearts was performed in 6 healthy baboons. The immunosuppression regimen included induction by anti-CD20 monoclonal antibodies (mAb), thymoglobulin, cobra venom factor, and anti-CD40 mAb, and maintenance with anti-CD40 mAb, mycophenolate mofetil, and tapering doses of steroids. Telemetry was used to assess graft function. Extracorporeal membrane oxygenation was used to support 1 recipient. A full human clinical transplantation team was involved in these experiments and the procedure was performed by skilled transplantation surgeons. RESULTS: A maximal survival of 40 hours was achieved in these experiments. The surgical procedures were uneventful, and all hearts were weaned from cardiopulmonary bypass without issue. Support with inotropes and vasopressors was generally required after separation from cardiopulmonary bypass. The cardiac xenografts performed well immediately, but within the first several hours they required increasing support and ultimately resulted in arrest despite maximal interventions. All hearts were explanted immediately; histology showed no signs of rejection. CONCLUSIONS: Despite excellent surgical technique, uneventful weaning from cardiopulmonary bypass, and adequate initial function, orthotopic cardiac xenografts slowly fail within 24 to 48 hours without evidence of rejection. Modification of preservation techniques and minimizing donor organ ischemic time may be able to ameliorate PCXD.

Fast spin exchange across a multielectron mediator.

Scalable quantum processors require tunable two-qubit gates that are fast, coherent and long-range. The Heisenberg exchange interaction offers fast and coherent couplings for spin qubits, but is intrinsically short-ranged. Here, we demonstrate that its range can be increased by employing a multielectron quantum dot as a mediator, while preserving speed and coherence of the resulting spin-spin coupling. We do this by placing a large quantum dot with 50-100 electrons between a pair of two-electron double quantum dots that can be operated and measured simultaneously. Two-spin correlations identify coherent spin-exchange processes across the multielectron quantum dot. We further show that different physical regimes of the mediated exchange interaction allow a reduced susceptibility to charge noise at sweet spots, as well as positive and negative coupling strengths up to several gigahertz. These properties make multielectron dots attractive as scalable, voltage-controlled coherent coupling elements.

Panniculectomy at the time of living donor renal transplantation: An 8-year experience.

Panniculectomy can be performed as a prophylactic procedure preceding transplantation to enable obese patients to meet criteria for renal transplantation. No literature exists on combined renal transplant and panniculectomy surgery (LRT-PAN). We describe our 8-year experience performing LRT-PAN. A retrospective chart review of all patients who had undergone LRT-PAN from 2010 to 2018 was conducted. Data were collected on patient demographics, allograft survival and function, and postoperative course. Fifty-eight patients underwent LRT-PAN. All grafts survived, with acceptable function at 1 year. Median length of stay was 4 days with a mean operative duration of 363 minutes. The wound complication rate was 24%. Ninety-day readmission rate was 52%, with medical causes as the most common reason for readmission (45%), followed by wound (32%) and graft-related complications (23%). Body mass index, diabetes status, and previous immunosuppression did not influence wound complication rate or readmission (P = .7720, P = .0818, and P = .4830, respectively). Combining living donor renal transplant and panniculectomy using a multidisciplinary team may improve access to transplantation, particularly for the obese and postobese population. This combined approach yielded shorter-than-expected hospital stays and similar wound complication rates, and thus should be considered for patients in whom transplantation might otherwise be withheld on the basis of obesity.

An Initial Investigation of Unmanned Aircraft Systems (UAS) and Real-Time Organ Status Measurement for Transporting Human Organs.

Organ transportation has yet to be substantially innovated. If organs could be moved by drone, instead of ill-timed commercial aircraft or expensive charter flights, lifesaving organs could be transplanted more quickly. A modified, six-rotor UAS was used to model situations relevant to organ transportation. To monitor the organ, we developed novel technologies that provided the real-time organ status using a wireless biosensor combined with an organ global positioning system. Fourteen drone organ missions were performed. Temperatures remained stable and low (2.5 °C). Pressure changes (0.37-0.86 kPa) correlated with increased altitude. Drone travel was associated with less vibration (<0.5 G) than was observed with fixed-wing flight (>2.0 G). Peak velocity was 67.6 km/h (42 m/h). Biopsies of the kidney taken prior to and after organ shipment revealed no damage resulting from drone travel. The longest flight was 3.0 miles, modeling an organ flight between two inner city hospitals. Organ transportation may be an ideal use-case for drones. With the development of faster, larger drones, long-distance drone organ shipment may result in substantially reduced cold ischemia times, subsequently improved organ quality, and thousands of lives saved.

Impact of antiretroviral regimen on renal transplant outcomes in HIV-infected recipients.

BACKGROUND: Protease inhibitors (PI) pose a challenge post-transplant due to significant drug interactions with calcineurin inhibitors, prompting many clinicians to convert patients to non-interacting regimens prior to transplant. The purpose of this study was to examine the impact of PI-based regimens on graft outcomes in HIV-infected renal transplant recipients. METHODS: In this retrospective cohort study, 50 HIV-infected renal allograft recipients (27 receiving a PI regimen, 23 receiving a non-PI regimen) transplanted between 2003-2015 were analyzed. RESULTS: Cumulative rejection rates at 12 and 36 months were 41% and 54% in the PI group vs 52% and 86% in the non-PI group. At last follow-up, the overall risk of acute rejection in the PI group was 46% lower compared with the non-PI cohort (P = 0.12). Patients who received a PI-based regimen had significantly reduced graft failure rates (P = 0.027). There was no difference between groups in the degree of interstitial fibrosis/tubular atrophy, arteriolar hyalinosis, arterial sclerosis, or glomerular sclerosis on available biopsies, despite longer follow-up time in the PI group. CONCLUSIONS: Our study suggests that PI-based antiretroviral therapy regimens are associated with improved graft survival and that patients can achieve adequate outcomes on a PI-based regimen when necessary. Due to study limitations, further studies are needed to determine the optimal immunosuppression/antiretroviral therapy regimen post-transplant.

Successful Renal Transplantation between Identical Twins with Very Brief Immunosuppression.

Renal transplantation between monozygous identical twins provides an opportunity to utilize minimal immunosuppression to maintain stable allograft function, thereby alleviating the toxicities of immunosuppressive therapy. Despite monozygosity, there is a possibility of discordant protein presentation in identical twins that could trigger alloimmune response and lead to graft injury. Therefore, the optimal immunosuppression regimen in this patient population is unknown, and the safety of immunosuppression withdrawal remains controversial. Herein, we describe two patients who underwent successful renal transplantation from monozygotic identical twin donors. Monozygosity was determined using short tandem repeat (STR) analysis. All immunosuppression was successfully discontinued at 2 days and 3 weeks, respectively, after transplantation. Both patients are alive with functioning renal grafts at 1 year and 5 years after transplant, respectively. These two cases suggest that immunosuppression can be withdrawn safely and rapidly in select monozygous identical twin renal transplant recipients.

Collaborative practice agreement in solid organ transplantation.

Background Given the complexity of solid organ transplant recipients, a multidisciplinary approach is required. To promote medication safety and enable providers to focus on the medical and surgical needs of these patients, our department of pharmacy created a collaborative practice agreement between physicians and pharmacists. Through this agreement, credentialed pharmacists are empowered to provide inpatient services including initiation and adjustment of medications through independent review of laboratory results after multidisciplinary rounds. Objective To evaluate the effect of our collaborative practice agreement on clinical care and institutional finances. Setting An inpatient setting at a large academic medical center. Methods Three transplant pharmacists entered all clinical interventions made on abdominal transplant recipients between September and October 2013 into Quantifi®, a software application that categorizes and assigns a cost savings value based on impact and type of intervention. Main outcome measure The main outcome measures in this study were number and categorization of interventions, as well as estimated cost savings to the institution. Results There were 1060 interventions recorded, an average of 20 interventions per pharmacist per day. The most common interventions were pharmacokinetic evaluations (36%) and dose adjustments (19%). Over the time period, these interventions translated into an estimated savings of $107,634.00, or an annual cost savings of $373,131.20 per pharmacist, or a cost-benefit ratio of 2.65 to the institution. Conclusions Based on our study, implementation of a collaborative practice agreement enables credentialed pharmacists to make clinically and financially meaningful interventions in a complex patient population.

Ultrahigh Error Threshold for Surface Codes with Biased Noise.

We show that a simple modification of the surface code can exhibit an enormous gain in the error correction threshold for a noise model in which Pauli Z errors occur more frequently than X or Y errors. Such biased noise, where dephasing dominates, is ubiquitous in many quantum architectures. In the limit of pure dephasing noise we find a threshold of 43.7(1)% using a tensor network decoder proposed by Bravyi, Suchara, and Vargo. The threshold remains surprisingly large in the regime of realistic noise bias ratios, for example 28.2(2)% at a bias of 10. The performance is, in fact, at or near the hashing bound for all values of the bias. The modified surface code still uses only weight-4 stabilizers on a square lattice, but merely requires measuring products of Y instead of Z around the faces, as this doubles the number of useful syndrome bits associated with the dominant Z errors. Our results demonstrate that large efficiency gains can be found by appropriately tailoring codes and decoders to realistic noise models, even under the locality constraints of topological codes.