Heisenberg Spin Bus as a Robust Transmission Line for Perfect State Transfer

We study the protocol known as quantum state transfer for a strongly coupled antiferromagnetic spin chain or ring (acting as a spin bus), with weakly coupled external qubits. By treating the weak coupling as a perturbation, we find that perfect state transfer (PST) is possible when second order terms are included in the expansion. We also show that PST is robust against variations in the couplings along the spin bus and between the bus and the qubits. As evidence of the quantum interference which mediates PST, we show that the optimal time for PST can be smaller with larger qubit separations, for an even-size chain or ring.Comment: 6 figures,submitte

Effect of Randomness on Quantum Data Buses of Heisenberg Spin Chains

A strongly coupled spin chain can mediate long-distance effective couplings or entanglement between remote qubits, and can be used as a quantum data bus. We study how the fidelity of a spin-1/2 Heisenberg chain as a spin bus is affected by static random exchange couplings and magnetic fields. We find that, while non-uniform exchange couplings preserve the isotropy of the qubit effective couplings, they cause the energy levels, the eigenstates, and the magnitude of the couplings to vary locally. On the other hand, random local magnetic fields lead to an avoided level crossing for the bus ground state manifold, and cause the effective qubit couplings to be anisotropic. Interestingly, the total magnetic moment of the ground state of an odd-size bus may not be parallel to the average magnetic field. Its alignment depends on both the direction of the average field and the field distribution, in contrast with the ground state of a single spin which always aligns with the applied magnetic field to minimize the Zeeman energy. Lastly, we calculate sensitivities of the spin bus to such local variations, which are potentially useful for evaluating decoherence when dynamical fluctuations in the exchange coupling or magnetic field are considered

Risk factors for prolonged hospitalization and delayed treatment completion after laparoscopic appendectomy in patients with uncomplicated acute appendicitis

Purpose We sought to identify the risk factors for prolonged hospitalization and delayed treatment completion after laparoscopic appendectomy in patients with uncomplicated acute appendicitis. Methods The study retrospectively analyzed 497 patients who underwent laparoscopic appendectomies for uncomplicated appendicitis between January 2018 and December 2020. The patients were divided into an early discharge group (≤2 days) and a late discharge group (>2 days) based on the length of hospital stay (LOS). The patients were also divided into uneventful and complicated groups according to the need for additional treatment after standard follow-up. Results Thirty-seven patients (7.4%) were included in the late discharge group. The mean LOS of the late discharge groups was 3.9 days. There were significant differences according to age, preoperative C-reactive protein (CRP), and operative time between the 2 groups. Only operative time was significantly associated with prolonged LOS in multivariate analysis. Thirty-five patients (7.0%) were included in the complicated group. The mean duration of treatment in the uneventful and complicated groups was 7.4 and 25.3 days, respectively. Significant differences existed between the uneventful and complicated groups in preoperative body temperature, preoperative CRP levels, maximal appendix diameter, and the presence of appendicoliths. In multivariate analysis, preoperative CRP levels and maximal appendix diameter were independent predictors of delayed treatment completion. Conclusion Shorter operative time is desirable to ensure minimal hospital stay in patients with uncomplicated appendicitis. Further efforts are needed to ensure that patients with uncomplicated appendicitis do not experience delayed treatment completion after laparoscopic appendectomies

Resonant Adiabatic Passage with Three Qubits

We investigate the non-adiabatic implementation of an adiabatic quantum teleportation protocol, finding that perfect fidelity can be achieved through resonance. We clarify the physical mechanisms of teleportation, for three qubits, by mapping their dynamics onto two parallel and mutually-coherent adiabatic passage channels. By transforming into the adiabatic frame, we explain the resonance by analogy with the magnetic resonance of a spin-1/2 particle. Our results establish a fast and robust method for transferring quantum states, and suggest an alternative route toward high precision quantum gates

Mediated gates between spin qubits

In a typical quantum circuit, nonlocal quantum gates are applied to nonproximal qubits. If the underlying physical interactions are short-range (e.g., exchange interactions between spins), intermediate swap operations must be introduced, thus increasing the circuit depth. Here we develop a class of "mediated" gates for spin qubits, which act on nonproximal spins via intermediate ancilla qubits. At the end of the operation, the ancillae return to their initial states. We show how these mediated gates can be used (1) to generate arbitrary quantum states and (2) to construct arbitrary quantum gates. We provide some explicit examples of circuits that generate common states [e.g., Bell, Greenberger-Horne-Zeilinger (GHZ), W, and cluster states] and gates (e.g.,square-root-SWAP, SWAP, CNOT, and Toffoli gates). We show that the depths of these circuits are often shorter than those of conventional swap-based circuits. We also provide an explicit experimental proposal for implementing a mediated gate in a triple-quantum-dot system.Comment: 12 pages, 8 figures, 2 table

Cancer Screening Literacy among Vietnamese Population: Does Annual Checkup Improve Cancer Screening Literacy?

© 2020. This work is licensed under a Creative Commons Attribution-Non Commercial 4.0 International License.Background: Colorectal, breast, and cervical cancers disproportionately impact the Vietnamese population. However, research on cancer prevention among this population was very limited. The purpose of this study is to examine the cancer screening literacy levels for these three types of cancers among rural Vietnamese and investigate correlates of cancer screening literacy. Methods: A sample of 226 Vietnamese men and women aged 25–70 years old was recruited from rural Vietnam and finished a self-administered questionnaire. Andersens Behavioral Model was used to guide this cross-sectional study to identify modifiable variables. Bivariate analysis was used to explore the relationship between demographic factors and cancer screening literacy levels. Multiple linear regressions were also used to identify significant factors for cancer literacy levels. Results: Cancer screening literacy levels of Vietnamese men and women were low regarding all three types of cancers, especially HPV symptom questions. Only about 24% of women answered correctly on most people with genital HPV have no visible signs/symptoms and less than 18% answered correctly on I can transmit HPV to my partner(s) even if I have no HPV symptoms. Findings suggested that having an annual checkup was associated with higher colorectal (β=.15, p<.05), breast (β=.25, p<.001), and cervical (β=.18, p<.01) cancer screening literacy. Conclusions: Public health efforts should focus on encouraging annual checkups in the Vietnamese population. During the annual checkup, health care professionals should educate patients about importance of cancer screening and provide recommendations for regular cancer screenings to reduce cancer health disparities.N