Electric field dependence of spin qubit in a Si-MOS quantum dot

Valley, the intrinsic feature of silicon, is an inescapable subject in silicon-based quantum computing. At the spin–valley hotspot, both Rabi frequency and state relaxation rate are significantly enhanced. With protection against charge noise, the valley degree of freedom is also conceived to encode a qubit to realize noise-resistant quantum computing.Here, based on the spin qubit composed of one or three electrons, we characterize the intrinsic properties of valley in an isotopically enriched silicon quantum dot(QD) device. For one-electron qubit, we measure two electric-dipole spin resonance(EDSR) signals which are attributed to partial occupation of two valley states. The resonance frequencies of two EDSR signals have opposite electric field dependences. Moreover, we characterize the electric field dependence of the upper valley state based on three-electron qubit experiments. The difference of electric field dependences of the two valleys is 52.02 MHz/V, which is beneficial for tuning qubit frequency to meet different experimental requirements. As an extension of electrical control spin qubits, the opposite electric field dependence is crucial for qubit addressability,individual single-qubit control and two-qubit gate approaches in scalable quantum computing.

Threshold-independent method for single-shot readout of spin qubits in semiconductor quantum dots

The single-shot readout data process is essential for the realization of high-fidelity qubits and fault-tolerant quantum algorithms in semiconductor quantum dots. However, the fidelity and visibility of the readout process are sensitive to the choice of the thresholds and limited by the experimental hardware. By demonstrating the linear dependence between the measured spin state probabilities and readout visibilities along with dark counts, we describe an alternative threshold-independent method for the single-shot readout of spin qubits in semiconductor quantum dots. We can obtain the extrapolated spin state probabilities of the prepared probabilities of the excited spin state through the threshold-independent method. We then analyze the corresponding errors of the method, finding that errors of the extrapolated probabilities cannot be neglected with no constraints on the readout time and threshold voltage. Therefore, by limiting the readout time and threshold voltage, we ensure the accuracy of the extrapolated probability. We then prove that the efficiency and robustness of this method are 60 times larger than those of the most commonly used method. Moreover, we discuss the influence of the electron temperature on the effective area with a fixed external magnetic field and provide a preliminary demonstration for a single-shot readout of up to 0.7K/1.5T in the future.

Esophagogastric junctional neuroendocrine tumor with adenocarcinoma:A case report

BACKGROUND At present,cases of esophageal neuroendocrine tumors combined with cardia adenocarcinoma are extremely rare worldwide,and there are no clinical reports.Herein,we describe such a case for clinical reference.CASE SUMMARY The presence of cardia cancer and esophageal neuroendocrine tumors in a single patient has not yet been reported.The patient in this case underwent prompt endoscopic treatment and additional surgical resection.Pathology revealed the following:The distance between the cardia cancer and the esophageal neuroendocrine tumors was small,approximately 3 mm.Vascular invasion was observed.The esophageal neuroendocrine tumor was determined to be grade G3.According to the treatment guidelines,after the patient received an explanation of their condition,additional surgical procedures were provided in a timely manner.Early detection and early treatment can successfully prolong survival and improve the quality of life of patients.CONCLUSION Early detection and early treatment can successfully prolong survival and improve the quality of life of such patients.