Dynamics of magnetization at infinite temperature in a Heisenberg spin chain.

Understanding universal aspects of quantum dynamics is an unresolved problem in statistical mechanics. In particular, the spin dynamics of the one-dimensional Heisenberg model were conjectured as to belong to the Kardar-Parisi-Zhang (KPZ) universality class based on the scaling of the infinite-temperature spin-spin correlation function. In a chain of 46 superconducting qubits, we studied the probability distribution of the magnetization transferred across the chain's center, [Formula: see text]. The first two moments of [Formula: see text] show superdiffusive behavior, a hallmark of KPZ universality. However, the third and fourth moments ruled out the KPZ conjecture and allow for evaluating other theories. Our results highlight the importance of studying higher moments in determining dynamic universality classes and provide insights into universal behavior in quantum systems.

Stable quantum-correlated many-body states through engineered dissipation.

Engineered dissipative reservoirs have the potential to steer many-body quantum systems toward correlated steady states useful for quantum simulation of high-temperature superconductivity or quantum magnetism. Using up to 49 superconducting qubits, we prepared low-energy states of the transverse-field Ising model through coupling to dissipative auxiliary qubits. In one dimension, we observed long-range quantum correlations and a ground-state fidelity of 0.86 for 18 qubits at the critical point. In two dimensions, we found mutual information that extends beyond nearest neighbors. Lastly, by coupling the system to auxiliaries emulating reservoirs with different chemical potentials, we explored transport in the quantum Heisenberg model. Our results establish engineered dissipation as a scalable alternative to unitary evolution for preparing entangled many-body states on noisy quantum processors.

Removing leakage-induced correlated errors in superconducting quantum error correction.

Quantum computing can become scalable through error correction, but logical error rates only decrease with system size when physical errors are sufficiently uncorrelated. During computation, unused high energy levels of the qubits can become excited, creating leakage states that are long-lived and mobile. Particularly for superconducting transmon qubits, this leakage opens a path to errors that are correlated in space and time. Here, we report a reset protocol that returns a qubit to the ground state from all relevant higher level states. We test its performance with the bit-flip stabilizer code, a simplified version of the surface code for quantum error correction. We investigate the accumulation and dynamics of leakage during error correction. Using this protocol, we find lower rates of logical errors and an improved scaling and stability of error suppression with increasing qubit number. This demonstration provides a key step on the path towards scalable quantum computing.

Diabatic Gates for Frequency-Tunable Superconducting Qubits.

We demonstrate diabatic two-qubit gates with Pauli error rates down to 4.3(2)×10^{-3} in as fast as 18 ns using frequency-tunable superconducting qubits. This is achieved by synchronizing the entangling parameters with minima in the leakage channel. The synchronization shows a landscape in gate parameter space that agrees with model predictions and facilitates robust tune-up. We test both iswap-like and cphase gates with cross-entropy benchmarking. The presented approach can be extended to multibody operations as well.

Fluctuations of Energy-Relaxation Times in Superconducting Qubits.

Superconducting qubits are an attractive platform for quantum computing since they have demonstrated high-fidelity quantum gates and extensibility to modest system sizes. Nonetheless, an outstanding challenge is stabilizing their energy-relaxation times, which can fluctuate unpredictably in frequency and time. Here, we use qubits as spectral and temporal probes of individual two-level-system defects to provide direct evidence that they are responsible for the largest fluctuations. This research lays the foundation for stabilizing qubit performance through calibration, design, and fabrication.

[An endoscopic method of the treatment of complicated acute calculous cholecystitis]. / Endoskopicheskii sposob lecheniia oslozhnennogo ostrogo kal'kuleznogo kholetsistita.

Surgical treatment of acute cholecystitis attended by an affection of the extrahepatic bile ducts often leads to severe complications, particularly in elderly and old-aged patients, the mortality rate in such cases reaches 5-12%. The authors developed and introduced into practice a method of endoscopic treatment of acute combined diseases of the gallbladder and bile ducts, which included endoscopic papillotomy, antegrade catheterization of the gallbladder (laparoscopic cholecystostomy, transhepatic gallbladder drainage), antegrade perfusion with antiseptics under pressure, and various types of ante- and retrograde lithotripsy. Endoscopic method of treatment of combined diseases of the gallbladder and bile ducts makes it possible to remove the acute inflammatory process and in some cases may be an alternative to an emergency surgical operation.

[Endoscopic diagnosis and treatment of tumors of the major duodenal papilla]. / Endoskopicheskaia diagnostika i lechenie opukholei bol'shogo duodenal'nogo sosochka.

Gastroduodenoscopy with target examination of the major duodenal papilla (MDP) and morphological study of the tumor, and endoscopic retrograde pancreatocholangiography were conducted in 104 patients with bening and malignant tumors of the MDP to establish the diagnosis. A precise diagnosis was made. Endoscopic papillotomy alone and in combination with nasobiliary drainage and endoprosthetics of the bile ducts were undertaken for therapeutic purposes in this category of patients. Analysis of the results showed that in cancer of the MDP, these methods can be the tool of treatment or an effective one of preoperative decompression, whereas in bening tumors of the MDP endoscopic papillotmy should be the method of choice.

[Endoscopic papillotomy in diseases of the extrahepatic bile ducts and major duodenal papilla]. / Endoskopicheskaia papillotomiia pri zabolevaniiakh vnepechenochnyk zhelchnykh protokov i bol'shogo duodenal'nogo soska.

An experience with using this operation in 500 patients aged from 22 to 90 is described. The authors suppose that endoscopic papillotomy in the majority of patients may be the method of treatment not requiring any additional curative measures. The application of not typical methods of operation makes the possibilities of endoscopic papillotomy wider in obstructive lesions of the major duodenal papilla.