Mechanically induced correlated errors on superconducting qubits with relaxation times exceeding 0.4 ms.

Superconducting qubits are among the most advanced candidates for achieving fault-tolerant quantum computing. Despite recent significant advancements in the qubit lifetimes, the origin of the loss mechanism for state-of-the-art qubits is still subject to investigation. Furthermore, the successful implementation of quantum error correction requires negligible correlated errors between qubits. Here, we realize long-lived superconducting transmon qubits that exhibit fluctuating lifetimes, averaging 0.2 ms and exceeding 0.4 ms - corresponding to quality factors above 5 million and 10 million, respectively. We then investigate their dominant error mechanism. By introducing novel time-resolved error measurements that are synchronized with the operation of the pulse tube cooler in a dilution refrigerator, we find that mechanical vibrations from the pulse tube induce nonequilibrium dynamics in highly coherent qubits, leading to their correlated bit-flip errors. Our findings not only deepen our understanding of the qubit error mechanisms but also provide valuable insights into potential error-mitigation strategies for achieving fault tolerance by decoupling superconducting qubits from their mechanical environments.

Topological lattices realized in superconducting circuit optomechanics.

Cavity optomechanics enables the control of mechanical motion through the radiation-pressure interaction1, and has contributed to the quantum control of engineered mechanical systems ranging from kilogramme-scale Laser Interferometer Gravitational-wave Observatory (LIGO) mirrors to nanomechanical systems, enabling ground-state preparation2,3, entanglement4,5, squeezing of mechanical objects6, position measurements at the standard quantum limit7 and quantum transduction8. Yet nearly all previous schemes have used single- or few-mode optomechanical systems. By contrast, new dynamics and applications are expected when using optomechanical lattices9, which enable the synthesis of non-trivial band structures, and these lattices have been actively studied in the field of circuit quantum electrodynamics10. Superconducting microwave optomechanical circuits2 are a promising platform to implement such lattices, but have been compounded by strict scaling limitations. Here we overcome this challenge and demonstrate topological microwave modes in one-dimensional circuit optomechanical chains realizing the Su-Schrieffer-Heeger model11,12. Furthermore, we realize the strained graphene model13,14 in a two-dimensional optomechanical honeycomb lattice. Exploiting the embedded optomechanical interaction, we show that it is possible to directly measure the mode functions of the hybridized modes without using any local probe15,16. This enables us to reconstruct the full underlying lattice Hamiltonian and directly measure the existing residual disorder. Such optomechanical lattices, accompanied by the measurement techniques introduced, offer an avenue to explore collective17,18, quantum many-body19 and quench20 dynamics, topological properties9,21 and, more broadly, emergent nonlinear dynamics in complex optomechanical systems with a large number of degrees of freedom22-24.

Entanglement-based single-shot detection of a single magnon with a superconducting qubit.

The recent development of hybrid systems based on superconducting circuits provides the possibility of engineering quantum sensors that exploit different degrees of freedom. Quantum magnonics, which aims to control and read out quanta of collective spin excitations in magnetically ordered systems, provides opportunities for advances in both the study of magnetism and the development of quantum technologies. Using a superconducting qubit as a quantum sensor, we report the detection of a single magnon in a millimeter-sized ferrimagnetic crystal with a quantum efficiency of up to 0.71. The detection is based on the entanglement between a magnetostatic mode and the qubit, followed by a single-shot measurement of the qubit state. This proof-of-principle experiment establishes the single-photon detector counterpart for magnonics.

Logical measurement-based quantum computation in circuit-QED.

We propose a new scheme of measurement-based quantum computation (MBQC) using an error-correcting code against photon-loss in circuit quantum electrodynamics. We describe a specific protocol of logical single-qubit gates given by sequential cavity measurements for logical MBQC and a generalised Schrödinger cat state is used for a continuous-variable (CV) logical qubit captured in a microwave cavity. To apply an error-correcting scheme on the logical qubit, we utilise a d-dimensional quantum system called a qudit. It is assumed that a three CV-qudit entangled state is initially prepared in three jointed cavities and the microwave qudit states are individually controlled, operated, and measured through a readout resonator coupled with an ancillary superconducting qubit. We then examine a practical approach of how to create the CV-qudit cluster state via a cross-Kerr interaction induced by intermediary superconducting qubits between neighbouring cavities under the Jaynes-Cummings Hamiltonian. This approach could be scalable for building 2D logical cluster states and therefore will pave a new pathway of logical MBQC in superconducting circuits toward fault-tolerant quantum computing.

Predictive value of plaque morphology assessed by frequency-domain optical coherence tomography for impaired microvascular perfusion after elective stent implantation: the intracoronary electrocardiogram study.

Aims: This study was undertaken to assess the association between plaque features at culprit lesions assessed by frequency-domain optical coherence tomography (FD-OCT) and impaired microvascular perfusion estimated by intracoronary electrocardiogram (IcECG) after elective percutaneous coronary intervention (PCI). Furthermore, we investigated whether IcECG could predict future cardiac events. Methods and results: This study consisted of 84 patients who underwent both FD-OCT and IcECG during PCI. Patients were classified into two groups based on ST-segment elevation (ST-E) on IcECG after the procedure; ST-E (-) group (n = 53) and ST-E (+) group (n = 31). Minimum fibrous cap thickness was significantly thinner in the ST-E (+) group than in the ST-E (-) group (240 µm [IQR 180 to 310] vs. 100 µm [IQR 60 to 120], P < 0.001). Plaque rupture (7.5% vs. 35.5%, P = 0.001), lipid-rich plaque (75.5% vs. 100%, P < 0.001), the thin cap fibroatheroma (0% vs. 25.8%, P < 0.001) on pre-FD-OCT, protrusion (18.9% vs. 56.7%, P < 0.001), and intra-stent dissection (15.1% vs. 50.0%, P < 0.001) on post-FD-OCT were significantly more frequently found in the ST-E (+) group than in the ST-E (-) group. The incidence of MACE (cardiac death, myocardial infarction, revascularization, hospitalization for heart failure) during 1-year was significantly higher in the ST-E (+) group than in the ST-E (-) group (5.7% vs. 19.4%, P < 0.05). Conclusion: Plaque features assessed by FD-OCT might be associated with impaired microvascular perfusion and ST-segment elevation on IcECG after the procedure could predict 1-year cardiac events after elective PCI.

Impact of Malondialdehyde-Modified Low-Density Lipoprotein on Tissue Characteristics in Patients With Stable Coronary Artery Disease　- Integrated Backscatter-Intravascular Ultrasound Study.

BACKGROUND: Malondialdehyde-modified low-density lipoprotein (MDA-LDL) is considered to play an essential role in plaque destabilization. We aimed to investigate the association between the tissue characteristics of culprit plaque assessed by integrated backscatter (IB)-intravascular ultrasound (IVUS) and the serum MDA-LDL levels in patients with stable coronary artery disease. METHODS AND RESULTS: The study group consisted of 179 patients undergoing IB-IVUS during elective percutaneous coronary intervention. Patients were classified into 2 groups based on serum MDA-LDL level: low MDA-LDL group (<102 U/L, n=88) and high MDA-LDL group (≥102 U/L, n=91). Plaques in the high MDA-LDL group had higher %lipid (45.2±12.5% vs. 54.9±14.5%, P<0.001) and lower %fibrosis (43.0±9.1% vs. 36.4±11.4%, P<0.001) than did plaques in the low MDA-LDL group. Lipid-rich plaque (%lipid >60% or %fibrosis <30%) was significantly more frequently found in the high MDA-LDL group than in the low MDA-LDL group (14.3% vs. 39.8%, P<0.001). The incidence of MACE (cardiac death, myocardial infarction and/or hospitalization for heart failure) during 3 years was significantly higher in the high MDA-LDL group than in the low MDA-LDL group (6.6% vs. 15.9%, P=0.02). CONCLUSIONS: Higher MDA-LDL might be associated with greater lipid and lower fibrous content, contributing to coronary plaque vulnerability. (Circ J 2016; 80: 2173-2182).

Novel Compression Tool to Prevent Hematomas and Skin Erosions After Device Implantation.

BACKGROUND: The incidence of hematoma formation following implantation of a cardiovascular implantable electronic device (CIED) is estimated to be 5% even if a pressure dressing is applied. It is unclear whether a pressure dressing can really compress the pocket in different positions. Furthermore, the adhesive tape for fixing pressure dressings can tear the skin. We developed a new compression tool for preventing hematomas and skin erosions. METHODS AND RESULTS: We divided 46 consecutive patients receiving anticoagulation therapy who underwent CIED implantation into 2 groups (Group I: conventional pressure dressing, Group II: new compression tool). The pressure on the pocket was measured in both the supine and standing positions. The incidence of hematomas was compared between the 2 groups. The pressure differed between the supine and standing positions in Group I, but not in Group II (Group I: 14.8±7.1 mmHg vs. 11.3±9.9 mmHg, P=0.013; Group II: 13.5±2.8 mmHg vs. 13.5±3.5 mmHg, P=0.99). The incidence of hematomas and skin erosions was documented in 2 (8.7%) and 3 (13%) Group I patients, respectively. No complications were documented in Group II. CONCLUSIONS: The new compression tool can provide adequate continuous pressure on the pocket, regardless of body position. This device may reduce the incidence of hematomas and skin erosions after CIED implantation.

Impaired coronary microvascular endothelial function in men with metabolic syndrome.

AIM: To assess coronary endothelial function of conduit and resistance vessels in patients with metabolic syndrome (MS). METHODS: Seventy-eight men (mean age, 57 years) with chest pain and angiographically normal coronary arteries were included in the study. Patients with coronary spastic angina were excluded. Changes in coronary artery diameter and coronary blood flow (CBF) in response to acetylcholine (ACh) were determined using quantitative coronary angiography and Doppler velocity measurements. Coronary flow reserve was calculated as the ratio of coronary blood velocity after adenosine triphosphate infusion relative to baseline values. Patients were divided into two groups based on the presence or absence of MS. RESULTS: There were 24 patients in the MS group (31%). The increase in CBF in response to ACh infusion was impaired in the MS group (P < 0.0001) compared to the non-MS group, whereas changes in coronary artery diameter in response to ACh infusion did not differ between the two groups. Multivariate regression analysis revealed that MS was a significant factor associated with the lesser change in CBF induced by ACh infusion at 30 µg/min (P < 0.0001, r(2) = 0.46). CONCLUSION: Coronary endothelial dysfunction was present at the level of resistance vessels but not conduit vessels in the MS patients included in our study.

[Investigation of reduction of exposure dose in digital mammography: relationship between exposure dose and image processing].

In digital mammograms, granularity is an important image property for the detection of microcalcifications and masses. Therefore, we investigated the relationship between the conditions of various exposure doses and the detectability of RMI156 phantom images with and without image processing for the reduction of exposure dose. The images are processed with Gaussian filter and unsharp-masking filters to evaluate the effects on image properties by using the digital Wiener spectrum (WS) presampled modulation transfer function (MTF). In addition, observer performance tests for the detectability of microcalcifications and masses are performed. With Gaussian filtering, the WS value decreased to 50% at 2.0 cycles/mm and the detectability score of masses increased 80% and 12%, on 1.34 mGy and 2.62 mGy, respectively (p<0.05). With unsharp-masking (7 x 7 pixels), the MTF value increased to 126% at 2.0 cycles/mm, and the detectability of microcalcification to 32% and 5%, on 1.34 mGy and 5.28 mGy, respectively (p<0.05) compared with the original image. The optimal dose of simulated lesions with unsharp masking became 5.25 mGy. The unsharp masking could reduce 37% of the exposure dose without a loss of detectability of microcalcifications and masses.