Encoding a magic state with beyond break-even fidelity.

To run large-scale algorithms on a quantum computer, error-correcting codes must be able to perform a fundamental set of operations, called logic gates, while isolating the encoded information from noise1-8. We can complete a universal set of logic gates by producing special resources called magic states9-11. It is therefore important to produce high-fidelity magic states to conduct algorithms while introducing a minimal amount of noise to the computation. Here we propose and implement a scheme to prepare a magic state on a superconducting qubit array using error correction. We find that our scheme produces better magic states than those that can be prepared using the individual qubits of the device. This demonstrates a fundamental principle of fault-tolerant quantum computing12, namely, that we can use error correction to improve the quality of logic gates with noisy qubits. Moreover, we show that the yield of magic states can be increased using adaptive circuits, in which the circuit elements are changed depending on the outcome of mid-circuit measurements. This demonstrates an essential capability needed for many error-correction subroutines. We believe that our prototype will be invaluable in the future as it can reduce the number of physical qubits needed to produce high-fidelity magic states in large-scale quantum-computing architectures.

High-Threshold Quantum Computing by Fusing One-Dimensional Cluster States.

We propose a measurement-based model for fault-tolerant quantum computation that can be realized with one-dimensional cluster states and fusion measurements only; basic resources that are readily available with scalable photonic hardware. Our simulations demonstrate high thresholds compared with other measurement-based models realized with basic entangled resources and 2-qubit fusion measurements. Its high tolerance to noise indicates that our practical construction offers a promising route to scalable quantum computing with quantum emitters and linear-optical elements.

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.

Torsional stability of the femur after harvest of the medial femoral condyle corticocancellous flap.

BACKGROUND: Increasingly large segments of medial femoral condyle (MFC) corticocancellous flaps have been harvested for transfer. Biomechanical evaluations demonstrated no osseous stability impairment under axial loading regardless of flap size harvested. The purpose of this study was to determine the donor site's response to torsional forces. METHODS: Dual-energy X-ray absorptiometry (DEXA) scanning was performed on 16 pairs of cadaver legs followed by removal of all soft tissues, except knee capsule and ligaments. Specimens were randomly assigned to three groups with bone harvest defects measuring 3, 5, or 7 cm in length and a control group with no osseous resection. Torsional load was applied until fracture or ligamentous failure. RESULTS: Bone failure rates were 12.5, 12.5, 28.6, and 55.6% for control, 3, 5, and 7 cm groups, respectively. Bone failure rate increased with increasing harvest size; the 7 cm group demonstrated a significantly higher rate compared with the other groups combined (55.6 vs. 17.4%; p = 0.03). Failure torque was 45.5, 29.35, 27.4, and 30.83 Nm for the control, 3, 5, and 7 cm groups, respectively (p = 0.11). Harvest of any size segment resulted in a significant decrease in failure torque (p = 0.01). Bone mineral density (BMD) and Z-scores were no different among groups (p = 0.79 and 0.59, respectively). A direct relationship was identified between force required for failure and BMD (p = 0.02) and Z-scores (p = 0.05) but not for failure location and BMD (p = 0.09) or Z-scores (p = 0.94). CONCLUSION: MFC corticocancellous flap harvest of any size decreases donor site failure torque. Flap harvests > 7 cm demonstrate a higher frequency of iatrogenic fracture and therefore warrant caution with torsional loading of the knee postoperatively. Routine preoperative DEXA scans may not be warranted.

Entropic barriers for two-dimensional quantum memories.

Comprehensive no-go theorems show that information encoded over local two-dimensional topologically ordered systems cannot support macroscopic energy barriers, and hence will not maintain stable quantum information at finite temperatures for macroscopic time scales. However, it is still well motivated to study low-dimensional quantum memories due to their experimental amenability. Here we introduce a grid of defect lines to Kitaev's quantum double model where different anyonic excitations carry different masses. This setting produces a complex energy landscape which entropically suppresses the diffusion of excitations that cause logical errors. We show numerically that entropically suppressed errors give rise to superexponential inverse temperature scaling and polynomial system size scaling for small system sizes over a low-temperature regime. Curiously, these entropic effects are not present below a certain low temperature. We show that we can vary the system to modify this bound and potentially extend the described effects to zero temperature.

Ertl below-knee amputation using a vascularized fibular strut in a nontrauma elderly population: a case series.

BACKGROUND: Tibiofibular bone bridging (Ertl) during a below-knee amputation (BKA) is used to create a stable bony platform, granting the patient improved rotary stability, higher end bearing potential, and ultimately, more functional ambulatory ability. However, limited data are available in the literature on actual patient outcomes, despite numerous reports of the technique. The purpose of this study was to report our experience with distal tibiofibular bone bridging using a vascularized fibular bone graft in an elderly nontrauma population. METHODS: We performed an institutional review board-approved, retrospective review of BKAs performed by the senior author between 2004 and 2011. Surgical indications, complications, and outcomes were recorded. A subgroup analysis and comparison was performed among patients that had received vascularized bone bridging and those that had not. RESULTS: A total of 294 BKAs were performed on 270 nontrauma patients. Of these, 30 (11%) were done on 29 patients with tibiofibular bone bridging. The mean clinical follow-up among the Ertl subgroup was 11 months (range, 1-42 months), and 17 months (range, 23 days-78 months) in the non-Ertl subgroup. The ambulation rate was 100% (29/29) in the Ertl group, and 78% (161/207) in the control group (P = 0.004). The overall rate of operative revision due to any etiology among groups did not differ significantly (P = 0.255). CONCLUSIONS: Tibiofibular bone bridging with vascularized fibula leads to a significantly higher rate of ambulation without a significantly higher rate of complications in a nontrauma population. Although this technique has been widely described in trauma patients, clinical data are lacking for the nontrauma population. This is the largest reported series of Ertl amputations in nontraumatic population to date and our results demonstrate a significant benefit of the Ertl technique in this population. LEVEL OF EVIDENCE: Level IV.

Topological entanglement entropy with a twist.

Defects in topologically ordered models have interesting properties that are reminiscent of the anyonic excitations of the models themselves. For example, dislocations in the toric code model are known as twists and possess properties that are analogous to Ising anyons. We strengthen this analogy by using the topological entanglement entropy as a diagnostic tool to identify properties of both defects and excitations in the toric code. Specifically, we show, through explicit calculation, that the toric code model including twists and dyon excitations has the same quantum dimensions, the same total quantum dimension, and the same fusion rules as an Ising anyon model.

Histological evaluation of a free medial femoral condyle flap at 21 months.

Recalcitrant nonunions typically require vascularized bone for reconstruction. In this report, we present a case of an index finger middle phalanx nonunion that was successfully treated with a free medial femoral condyle corticocancellous flap. Nearly 2 years after the free tissue transfer, the patient underwent debulking of the bone flap. This gave us the unique opportunity to examine the histology of the vascularized bone.

Amputation and ambulation in diabetic patients: function is the goal.

The role of amputation in limb salvage is often poorly defined because the surgeon and the patient often attempt to save all limbs at all costs. The difficulty lies in selecting limb salvage versus early amputation. For the sedentary patient, a poorly functional salvaged limb can provide him/her with a higher quality of life than he/she would have with an amputation. For the active patient, early major amputation may offer the best functional outcome. Our experience with diabetic limb salvage over the last 20 years was retrospectively reviewed and compared with the existing literature in an attempt to better understand the role of amputation versus limb salvage in patients with diabetes. In the process, surgical techniques that we believe optimize foot and leg amputations were reviewed. Utilizing a team approach, limb salvage can yield a 64% ambulation rate and an 80% 2-year survival rate. Below-knee amputation led to a similar ambulatory rate, but the 2-year survival in these patients was 52%. With more severe rear-foot ulcers and osteomyelitis, the ambulatory rate declined with each comorbidity. However, those whose foot was saved had a higher chance of walking than those who underwent amputation. Function and quality of life are the outcomes of interest and may be maximized through either limb salvage or amputation. Our job as physicians is to match the correct solution to the patients' lifestyle and their medical, physical and psychological conditions so they can achieve their desired level of activity as quickly as possible.

Plastic surgery training: evaluating patient satisfaction with facial fillers in a resident clinic.

BACKGROUND: Resident cosmetic surgery clinics, or "chief clinics," are arguably the most effective way to provide cosmetic surgery training. Approximately 70 % of plastic surgery training programs utilize a "chief resident clinic" to augment their cosmetic surgery experience, even though a quantitative outcome scale is lacking to guide education. We report the use of the FACE-Q, a novel patient outcome tool, to evaluate patients' satisfaction with nonsurgical facial rejuvenation performed by residents. METHODS: The FACE-Q "Satisfaction with Facial Appearance Overall Scale" was administered to patients prior to and 1 week after undergoing nonsurgical facial rejuvenation performed by plastic surgery residents. All patients received nonsurgical facial rejuvenation with botulinum toxin A and hyaluronic acid as part of resident facial aesthetics training. RESULTS: Eleven patients completed the pre- and postinjection FACE-Q survey. Average overall facial appearance satisfaction scores of 47.6 pre- and 51.1 postinjection were found (p < 0.037), with a total possible score of 68. Ten patients (91 %) reported feeling satisfied or very satisfied with the overall appearance of their face following injection. CONCLUSION: Despite resident inexperience and patient awareness that novices were performing the procedures, our experience supports use of the FACE-Q to optimize and endorse resident cosmetic surgery clinics. The learning curve for facial cosmetic procedures can be adversely affected by limited time available or exposure to improvement variables when initially performing the procedure. It is imperative to any technique that direct, and preferably quantitative, feedback is given so that an immediate modification can be generated and successive patient outcomes improved. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

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.

Lower extremity free flap reconstruction outcomes using venous coupler.

BACKGROUND: Microvascular anastomotic coupling devices have been available to microsurgeons for over 20 years. Many studies have validated the efficacy of these devices for venous anastomosis. To date, there have been no large reports of their success in the anatomical region with the highest free flap failure rate, the lower extremity. METHODS: A retrospective review of 67 consecutive patients who underwent lower extremity microvascular reconstruction performed from August 2003 to September 2010 was performed. Patient charts were reviewed for age, sex, medical comorbidities, etiology of defect, location of defect, flap type, anastomotic technique, complications, flap survival, and limb salvage outcome. RESULTS: No patients returned to the operating room to have an arterial or venous anastomosis revised. Despite 100% vascular anastomosis patency rates in 67 consecutive lower extremity free flaps, flap survival rate was 95.5%. Total complication rate (13.4%) was due to two partial and one complete flap loss, three infections, two skin graft loses, and one hematoma. There were no intraoperative or perioperative complications involving the use of a microvascular anastomotic coupling device itself. Thirty-day and long term limb salvage rate was 97% and 92.5%, respectively. CONCLUSION: Microvascular anastomotic coupling devices create effective venous anastomoses in lower extremity microvascular reconstruction. Thus, it presents an important tool in the armamentarium for lower extremity microsurgical reconstruction.

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.

Hospitalizations for pediatric stone disease in United States, 2002-2007.

PURPOSE: Although more common in adults, urolithiasis recently has been occurring with increasing frequency in children. Single institution reviews from 1950 to 1990 revealed that urolithiasis accounts for 1 in 7,600 to 1 in 1,000 pediatric hospitalizations. Stone prevalence and risk factors for hospitalization are less defined in children in North America compared to adults. To identify pediatric hospital admissions due to a diagnosis of urinary stones, we examined Pediatric Health Information System data from 41 freestanding pediatric hospitals. MATERIALS AND METHODS: We retrospectively studied patients younger than 18 years hospitalized between 2002 and 2007. The Pediatric Health Information System database, a validated collection of pediatric hospital data, was searched for inpatients with a primary ICD-9 diagnosis of urolithiasis. RESULTS: Among more than 2.7 million pediatric inpatients from 2002 to 2007, 3,989 hospitalizations were for 3,815 patients with urolithiasis. In contrast to adults, girls had a 1.5-fold greater likelihood of being hospitalized for stones. More than half of the children (53.1%) were younger than 13 years (mean 12.3, SD 4.23). Most patients (88%) were white. Stone hospitalizations were more common in the North Central region compared to the South. Hospitalizations for stones increased slightly in August and September. Nephrectomy was performed in nearly 1% of stone hospitalizations (29 of 3,170). CONCLUSIONS: Children with stones now account for 1 in 685 pediatric hospitalizations in the United States. Surprisingly more than half of the patients are younger than 13 years at hospitalization. Similar to findings in adults, white race and occurrence in late summer months increase the risk of stone hospitalization. However, male gender and geographic location in the Southeast are not risk factors, demonstrating the unique aspects of pediatric stone hospitalization.

A fault-tolerant non-Clifford gate for the surface code in two dimensions.

Fault-tolerant logic gates will consume a large proportion of the resources of a two-dimensional quantum computing architecture. Here we show how to perform a fault-tolerant non-Clifford gate with the surface code; a quantum error-correcting code now under intensive development. This alleviates the need for distillation or higher-dimensional components to complete a universal gate set. The operation uses both local transversal gates and code deformations over a time that scales with the size of the qubit array. An important component of the gate is a just-in-time decoder. These decoding algorithms allow us to draw upon the advantages of three-dimensional models using only a two-dimensional array of live qubits. Our gate is completed using parity checks of weight no greater than four. We therefore expect it to be amenable with near-future technology. As the gate circumvents the need for magic-state distillation, it may reduce the resource overhead of surface-code quantum computation considerably.

Nipple-areolar complex reconstruction and patient satisfaction: a systematic review and meta-analysis.

BACKGROUND: Nipple-areola complex (NAC) reconstruction transforms a mound of soft tissue into a breast and often marks the final stage of breast reconstruction after mastectomy. METHODS: A systematic review and meta-analysis were conducted in accordance with the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines. Articles were classified based on the nipple reconstructive technique-either composite nipple sharing or local flap with nipple-sparing mastectomy (NSM) used as a control. A standardized "Satisfaction Score" (SS) for "nipple appearance" and "nipple sensation" was calculated for each technique. A Fisher's exact test was used to compare the SS with local flap reconstruction with NSM. RESULTS: Twenty-three studies met the systematic review inclusion criteria. Nine NSM articles were identified with patient satisfaction data from 473 patients. The weighted average SS for NSM was 80.5%. Fourteen local flap technique articles were identified with satisfaction data from 984 patients and a weighted average SS of 73.9%. This was a statistically significant difference (P=0.0079). C-V and badge local flap techniques were associated with the highest SS, 92.6% and 90.5%, respectively. C-V and modified C-V flap technique was associated with a higher SS when compared to those using one or more other flap techniques (P=0.0001). CONCLUSIONS: While patient satisfaction with nipple reconstruction is high regardless of technique, it is higher with NSM. When NSM is not an option, local flap reconstruction with a C-V or modified C-V flap may be associated with higher satisfaction than alternative local flap techniques.

Fault-tolerant error correction with the gauge color code.

The constituent parts of a quantum computer are inherently vulnerable to errors. To this end, we have developed quantum error-correcting codes to protect quantum information from noise. However, discovering codes that are capable of a universal set of computational operations with the minimal cost in quantum resources remains an important and ongoing challenge. One proposal of significant recent interest is the gauge color code. Notably, this code may offer a reduced resource cost over other well-studied fault-tolerant architectures by using a new method, known as gauge fixing, for performing the non-Clifford operations that are essential for universal quantum computation. Here we examine the gauge color code when it is subject to noise. Specifically, we make use of single-shot error correction to develop a simple decoding algorithm for the gauge color code, and we numerically analyse its performance. Remarkably, we find threshold error rates comparable to those of other leading proposals. Our results thus provide the first steps of a comparative study between the gauge color code and other promising computational architectures.

Reducing Wound Tension with Undermining or Imbrication-Do They Work?

BACKGROUND: For the noncolonized wound, achieving tension-free, primary wound closure is ideal. Some surgeons advocate imbrication of deeper tissues rather than undermining, posing that imbrication preserves more dermal perfusion while still reducing tension at the wound edge. We sought to determine which technique most reliably reduced wound tension while preserving dermal wound perfusion. METHODS: A total of 5 standardized, symmetrical pairs of full thickness wounds were created on Duroc swine. Wound tension was measured with a Tyrolean tensiometer before and after either method of closure, whereas a speckle contrast imager was used to assess dermal edge perfusion. Skin tension and dermal perfusion were evaluated for statistical significance via paired t tests and a multivariate analysis of variance. RESULTS: There was a significant reduction in wound tension with undermining and imbrication relative to the raw wound tension (5 and 5.9 vs 7.1 N; P < 0.05) yet no significant difference between methods of closure (P > 0.05). There was a significant reduction in dermal perfusion between unwounded skin and the imbricated wound (222 perfusion units [PU] vs 48 PU; P < 0.05) and between the unwounded skin and the undermined wound (205 vs 63 PU; P < 0.05). CONCLUSIONS: We found no significant difference in wound tension between wound undermining or imbrication and a significant decrease in dermal perfusion after imbrication and undermining although the relative decrease in perfusion was greater with imbrication. Wound undermining reduces skin tension with greater relative dermal perfusion to the skin and should be selected over wound imbrication in standard primary wound closure.

Through knee amputation: technique modifications and surgical outcomes.

BACKGROUND: Knee disarticulations (KD) are most commonly employed following trauma or tumor resection but represent less than 2% of all lower extremity amputations performed in the United States annually. KDs provide enhanced proprioception, a long lever arm, preservation of adductor muscle insertion, decreased metabolic cost of ambulation, and an end weight-bearing stump. The role for KDs in the setting of arterial insufficiency or overwhelming infection is less clear. The purpose of this study is to describe technique modifications and report surgical outcomes following KDs at a high-volume Limb Salvage Center. METHODS: A retrospective study of medical records for all patients who underwent a through-knee amputation performed by the senior author (C.E.A.) between 2004 and 2012 was completed. Medical records were reviewed to collect demographic, operative, and postoperative information for each of the patients identified. RESULTS: Between 2004 and 2012, 46 through-knee amputations for 41 patients were performed. The mean patient age was 68 and indications for surgery included infection (56%), arterial thrombosis (35%), and trauma (9%). Postoperative complications included superficial cellulitis (13%), soft tissue infection (4%), and flap ischemia (4%) necessitating one case of surgical debridement (4%) and four trans-femoral amputations (9%). 9 (22%) patients went on to ambulate. Postoperative ambulation was greatest in the traumatic cohort and for patients less than 50 years of age, P<0.05. Alternatively, diabetes mellitus and infection reduced the likelihood of postoperative ambulation, P<0.01. CONCLUSIONS: Knee disarticulations are a safe and effective alternative to other lower extremity amputations when clinically feasible. For patient unlikely to ambulate, a through-knee amputation maximizes ease of transfers, promotes mobility by providing a counterbalance, and eliminates the potential for knee flexion contracture with subsequent skin breakdown.

Outcomes after 294 transtibial amputations with the posterior myocutaneous flap.

The transtibial amputation is a common operation for which there is little agreement regarding which technique provides the most reliable and resilient outcomes. We performed a retrospective chart review of all transtibial amputations performed by a single surgeon between 2004 and 2011 using the posterior myocutaneous flap with triceps surae myodesis technique. A stepwise logistic regression analysis was performed to evaluate the association between independent variables and dependent outcome variables. A total of 270 patients with 294 transtibial amputations were identified. Ambulation data were available for 192 patients with a mean follow-up 18.4 months. This cohort had an overall ambulation rate of 75%, a 12% incidence of stump wounds, 24% operative revision rate and only 2% required conversion to a transfemoral amputation. The posterior myocutaneous flap provides durable and reliable soft tissue coverage in the setting of a transtibial amputation.