Digital quantum simulation of NMR experiments.

Simulations of nuclear magnetic resonance (NMR) experiments can be an important tool for extracting information about molecular structure and optimizing experimental protocols but are often intractable on classical computers for large molecules such as proteins and for protocols such as zero-field NMR. We demonstrate the first quantum simulation of an NMR spectrum, computing the zero-field spectrum of the methyl group of acetonitrile using four qubits of a trapped-ion quantum computer. We reduce the sampling cost of the quantum simulation by an order of magnitude using compressed sensing techniques. We show how the intrinsic decoherence of NMR systems may enable the zero-field simulation of classically hard molecules on relatively near-term quantum hardware and discuss how the experimentally demonstrated quantum algorithm can be used to efficiently simulate scientifically and technologically relevant solid-state NMR experiments on more mature devices. Our work opens a practical application for quantum computation.

Copula-based risk aggregation with trapped ion quantum computers.

Copulas are mathematical tools for modeling joint probability distributions. In the past 60 years they have become an essential analysis tool on classical computers in various fields. The recent finding that copulas can be expressed as maximally entangled quantum states has revealed a promising approach to practical quantum advantages: performing tasks faster, requiring less memory, or, as we show, yielding better predictions. Studying the scalability of this quantum approach as both the precision and the number of modeled variables increase is crucial for its adoption in real-world applications. In this paper, we successfully apply a Quantum Circuit Born Machine (QCBM) based approach to modeling 3- and 4-variable copulas on trapped ion quantum computers. We study the training of QCBMs with different levels of precision and circuit design on a simulator and a state-of-the-art trapped ion quantum computer. We observe decreased training efficacy due to the increased complexity in parameter optimization as the models scale up. To address this challenge, we introduce an annealing-inspired strategy that dramatically improves the training results. In our end-to-end tests, various configurations of the quantum models make a comparable or better prediction in risk aggregation tasks than the standard classical models.

Case report: a case of multiple splenic abscesses in a child and literature review.

Splenic abscesses in children are very rare, and multiple splenic abscesses are rarer. These lesions are difficult to diagnose quickly because of their low incidence and the low specificity of the associated clinical and imaging findings. The treatment of splenic abscesses includes conservative treatment, percutaneous drainage, and splenectomy, but the selection criteria for treatment are still unclear. We present a case of a 13-year-old girl with multiple splenic abscesses. Her blood culture report was negative. We eventually confirmed the diagnosis by enhanced magnetic resonance imaging (MRI). The patient underwent a successful laparoscopic total splenectomy, and her symptoms were resolved thereafter.

Value of gallbladder length-to-width ratio for diagnosis of biliary atresia by correlation with age.

The objective is to explore the correlation between ultrasonic gallbladder length-width ratio (LTWR) and age, and the value of differential diagnosis between biliary atresia (BA) and other hepatic cholestasis. From January 2016 to June 2022, the data of 183 patients with jaundice who underwent abdominal ultrasound and surgical exploration in the Affiliated Hospital of Zunyi Medical University were analyzed retrospectively. The demographic data, liver function, and ultrasonic parameters were recorded and analyzed. There were statistically significant differences between BA group and non-BA group in maximum length, maximum width and LTWR of gallbladder (P < 0.001). In all age groups (I: ≤ 30 days; II: 31-60 days; III: 61-90 days; IV: 91-120 days; V: ≥ 121 days), in which group III (61-90 days) had the highest area under the curve (AUC) of 0.843, and group V (≥121 days) had the lowest AUC of 0.548. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of gallbladder LTWR > 3.26 for BA in group II (31-60 days) were 78.9%, 75.0%, 75.0%, 78.9% and 76.9%, respectively. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of gallbladder LTWR > 3.69 for BA in group III (61-90 days) were 76.6%, 84.6%, 92.5%, 59.5% and 78.9%, respectively. Ultrasonography LTWR of gallbladder has certain value in the diagnosis of BA. The diagnostic value of gallbladder LTWR in infants with different ages was quite different, and it was relatively high in infants with 31-90 days.

Thoracoscopic surgery for congenital diaphragmatic hernia in neonates: Should it be the first choice?

Objective: Congenital diaphragmatic hernia (CDH) is an uncommon but potentially life-threatening surgical condition in neonates. Surgery can be performed by either open or thoracoscopic techniques. In this study, we compared the clinical efficacy, safety, and effectiveness of thoracoscopic and open CDH repair. Methods: A retrospective review of neonates with CDH who underwent operations at our hospital from 2013 to 2021 was performed. The various perioperative parameters were compared between neonates undergoing thoracoscopic and open surgery. Results: There were 50 neonates in this study (37 in the thoracoscopic group and 13 in the open group). Thoracoscopic surgery was associated with significantly shorter hospital stay (13.32 vs. 18.77 days, p < 0.001); shorter duration of postoperative mechanical ventilation (3.70 vs. 5.98 days, p < 0.001); early feeding (4.34 vs. 7.46 days, p < 0.001); and shorter time to reach optimal feeding (8.21 vs. 13.38 days, p < 0.001). There was one postoperative death in the open group and no death in the thoracoscopic group. The median follow-up time of the two groups was 23.8 months (20.5 months in open group and 25.0 months in thoracoscopic group). Thoracoscopic surgery was associated with lower recurrence rates, but the difference was not statistically significant (2.7% vs. 7.7%, p = 0.456). Conclusion: Thoracoscopy CDH repair, a safe and effective surgical technique for neonates, has better cosmesis, faster postoperative recovery, and a lower recurrence rate than other procedures. It can be considered the first choice for CDH treatment for neonates among experienced surgeons.

Relationship between the expression levels of CD4+ T cells, IL-6, IL-8 and IL-33 in the liver of biliary atresia and postoperative cholangitis, operative age and early jaundice clearance.

OBJECTIVE: To investigate the expression levels of CD4+ T cells, IL-6, IL-8 and IL-33 in liver tissue of BA, and the relationship with postoperative cholangitis, operative age and early jaundice clearance. METHODS: 45 cases of jaundice treated in the hospital from June 2018 to May 2020 were analyzed retrospectively. The expression and distribution of these factors were detected by HE staining and immunohistochemistry, the total bilirubin level and the incidence of cholangitis were recorded, and the relationship between liver inflammation level and the postoperative incidence of cholangitis, age of operation and early jaundice clearance were compared. RESULTS: Immunohistochemistry showed that the expression of CD4+ T cells, IL-6, IL-8 and IL-33 in the BA group were higher than those in the CBD group. ROC curve analysis showed the AUC of CD4+ T cells, IL-6 and IL-8 were 0.869, 0.886 and 0.838, respectively. The expression level of CD4+ T cells was negatively correlated with the decline rate of TBIL 3 months after operation, and the expressions of IL-8 and IL-33 were negatively correlated with the decline rate of TBIL 1 week after operation. CONCLUSION: The high expression of CD4+ T cells, IL-6, IL-8 and IL-33 in the BA liver tissue may lead to cholangitis and can be used as a predictor of early jaundice clearance. The degree of liver inflammation infiltration had nothing to do with the age of operation and is not a risk factor for postoperative cholangitis.

Comparative analysis of cystic biliary atresia and choledochal cysts.

Objective: Cystic biliary atresia (CBA) is a rare and peculiar type of biliary atresia (BA) that is easily confused with infantile choledochal cysts (CCs). This study explored information for early CBA diagnosis and treatment. Method: The authors retrospectively analyzed the clinical data of 32 children with hilar cysts from January 2013 to May 2021. According to the diagnosis, they were divided into the CBA (n = 12) and CC (n = 20) groups. Patient features, biochemical indexes, preoperative ultrasound characteristics, cholangiography features, and intraoperative findings were analyzed and compared between the two groups. Results: The alanine aminotransferase, aspartate aminotransferase, total bilirubin, and direct bilirubin levels in the CBA group were higher than in the CCs group (P < 0.05). Additionally, B-mode ultrasound showed a cystic mass in front of the hepatic hilum, and the cyst size was much smaller in the CBA group compared with the CC group (2.2 ± 1.3 cm vs. 6.0 ± 2.2 cm, P < 0.001). Among all of the parameters, cyst width was the most accurate for identifying CBA and CCs. A cutoff value of 2.5 cm (area under the curve, 0.98, P < 0.001) showed 90.9% sensitivity and 95% specificity for cyst size. Conclusion: For children with early-onset severe jaundice, and if the width of the cystic mass was ≤2.5 cm, a diagnosis of CBA was highly likely. Early cholangiography and surgical treatment are necessary for the effective treatment of these infants.

Optimizing Stabilizer Parities for Improved Logical Qubit Memories.

We study variants of Shor's code that are adept at handling single-axis correlated idling errors, which are commonly observed in many quantum systems. By using the repetition code structure of the Shor's code basis states, we calculate the logical channel applied to the encoded information when subjected to coherent and correlated single qubit idling errors, followed by stabilizer measurement. Changing the signs of the stabilizer generators allows us to change how the coherent errors interfere, leading to a quantum error-correcting code which performs as well as a classical repetition code of equivalent distance against these errors. We demonstrate a factor of 3.78±1.20 improvement of the logical T2^{*} in a distance-3 logical qubit implemented on a trapped-ion quantum computer. Even-distance versions of our Shor-code variants are decoherence-free subspaces and fully robust to identical and independent coherent idling noise.

Fault-tolerant control of an error-corrected qubit.

Quantum error correction protects fragile quantum information by encoding it into a larger quantum system1,2. These extra degrees of freedom enable the detection and correction of errors, but also increase the control complexity of the encoded logical qubit. Fault-tolerant circuits contain the spread of errors while controlling the logical qubit, and are essential for realizing error suppression in practice3-6. Although fault-tolerant design works in principle, it has not previously been demonstrated in an error-corrected physical system with native noise characteristics. Here we experimentally demonstrate fault-tolerant circuits for the preparation, measurement, rotation and stabilizer measurement of a Bacon-Shor logical qubit using 13 trapped ion qubits. When we compare these fault-tolerant protocols to non-fault-tolerant protocols, we see significant reductions in the error rates of the logical primitives in the presence of noise. The result of fault-tolerant design is an average state preparation and measurement error of 0.6 per cent and a Clifford gate error of 0.3 per cent after offline error correction. In addition, we prepare magic states with fidelities that exceed the distillation threshold7, demonstrating all of the key single-qubit ingredients required for universal fault-tolerant control. These results demonstrate that fault-tolerant circuits enable highly accurate logical primitives in current quantum systems. With improved two-qubit gates and the use of intermediate measurements, a stabilized logical qubit can be achieved.

Many-body thermodynamics on quantum computers via partition function zeros.

Partition functions are ubiquitous in physics: They are important in determining the thermodynamic properties of many-body systems and in understanding their phase transitions. As shown by Lee and Yang, analytically continuing the partition function to the complex plane allows us to obtain its zeros and thus the entire function. Moreover, the scaling and nature of these zeros can elucidate phase transitions. Here, we show how to find partition function zeros on noisy intermediate-scale trapped-ion quantum computers in a scalable manner, using the XXZ spin chain model as a prototype, and observe their transition from XY-like behavior to Ising-like behavior as a function of the anisotropy. While quantum computers cannot yet scale to the thermodynamic limit, our work provides a pathway to do so as hardware improves, allowing the future calculation of critical phenomena for systems beyond classical computing limits.

Quantum walks and Dirac cellular automata on a programmable trapped-ion quantum computer.

The quantum walk formalism is a widely used and highly successful framework for modeling quantum systems, such as simulations of the Dirac equation, different dynamics in both the low and high energy regime, and for developing a wide range of quantum algorithms. Here we present the circuit-based implementation of a discrete-time quantum walk in position space on a five-qubit trapped-ion quantum processor. We encode the space of walker positions in particular multi-qubit states and program the system to operate with different quantum walk parameters, experimentally realizing a Dirac cellular automaton with tunable mass parameter. The quantum walk circuits and position state mapping scale favorably to a larger model and physical systems, allowing the implementation of any algorithm based on discrete-time quantum walks algorithm and the dynamics associated with the discretized version of the Dirac equation.