Fast generation of Schrödinger cat states using a Kerr-tunable superconducting resonator.

Schrödinger cat states, quantum superpositions of macroscopically distinct classical states, are an important resource for quantum communication, quantum metrology and quantum computation. Especially, cat states in a phase space protected against phase-flip errors can be used as a logical qubit. However, cat states, normally generated in three-dimensional cavities and/or strong multi-photon drives, are facing the challenges of scalability and controllability. Here, we present a strategy to generate and preserve cat states in a coplanar superconducting circuit by the fast modulation of Kerr nonlinearity. At the Kerr-free work point, our cat states are passively preserved due to the vanishing Kerr effect. We are able to prepare a 2-component cat state in our chip-based device with a fidelity reaching 89.1% under a 96 ns gate time. Our scheme shows an excellent route to constructing a chip-based bosonic quantum processor.

[Topography-guided transepithelial corneal collagen cross-linking by sequential ultraviolet A irradiation in different diameters for progressive keratoconus in adults].

Objective: To compare the efficacy and safety of a novel customized topography-guided transepithelial corneal collagen cross-linking (TG-CXL) procedure by sequential ultraviolet A irradiation in different diameters and conventional transepithelial corneal collagen cross-linking (TE-CXL) in adult patients with progressive keratoconus. Methods: A prospective cohort study was conducted. Adult patients diagnosed with progressive keratoconus in the Affiliated Xiamen Eye Center of Xiamen University were continuously recruited and randomly assigned to receive the TG-CXL or TE-CXL procedure from March 2020 to March 2021. Patients in the TE-CXL group were irradiated in the central 9-mm zone of the cornea (total energy, 7.2 J/cm2; irradiance, 45 mW/cm2), while patients in the TG-CXL group were first irradiated with the protocol used in the TE-CXL group, and further irradiated in the central 6-mm zone (total energy, 3.6 J/cm2; irradiance, 9 mW/cm2). The subjective symptom of pain and corneal fluorescein sodium staining were scored within postoperative 3 days. Slit lamp examination, measurements of uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), corneal topography, anterior segment optical coherence tomography, in vivo corneal confocal microscopy, corneal endothelial cell count, and non-contact tonometry were performed before surgery and at 3, 6, and 12 months after surgery. Results: A total of 66 patients were enrolled (mean age, 23.0±3.3 years old), with 33 patients (33 eyes) in each group. No statistically significant differences were found in age, gender, and maximum keratometry (Kmax) between the two groups (P>0.05). On day 1 after surgery, the average pain score of the TG-CXL group (2.21±0.45) was significantly higher than that of the TE-CXL group (1.32±0.33) (P<0.05). The pain was rapidly alleviated in both groups on days 2 and 3. On days 1 and 2, the corneal fluorescein sodium staining scores in the TG-CXL group (4.15±0.83 and 2.21±0.60, respectively) were significantly higher than those in the TE-CXL group (1.76±0.56 and 0.85±0.51, respectively, P<0.001), while there was no significant difference between the two groups at day3 (P=0.184). The UCVA and BCVA of the TG-CXL group at 3, 6, and 12 months after surgery were significantly improved when compared with the baseline. At 3, 6, and 12 months, the BCVA (LogMAR) of the TG-CXL group (0.21±0.15, 0.22±0.16, and 0.22±0.16, respectively) were significantly improved when compared with those of the TE-CXL group(0.32±0.15, 0.34±0.15, and 0.36±0.16, respectively, P<0.01). However, there was no significant difference in UCVA between groups at any time point after surgery (P>0.05). The spherical and cylindrical power values of the TG-CXL group were improved when compared with the baseline (P<0.05). However, no significant difference in spherical power values was found between the two groups at any time point after surgery (P>0.05). Meanwhile, there were significant differences in cylindrical power values between the two groups at 6 and 12 months after surgery (P<0.05). The Kmax in the TG-CXL group was improved at all of the time points after surgery when compared with the baseline (P<0.001), while no significant difference in Kmax was found at any time point after surgery in the TE-CXL group when compared with the baseline (P>0.05). At 6 and 12 months after surgery, the Kmax values in the TG-CXL group were significantly lower than the TE-CXL group (P<0.05). No significant differences were found in flat keratomety, steep keratometry, the minimal thickness of the cornea, endothelial cell density, and intraocular pressure between the two groups at any time point after surgery (P>0.05). Within one month after surgery, optical coherence tomography revealed the increased density in the anterior stroma in both groups. In most patients in the TG-CXL group, a demarcation line was visible in the central and para-central corneal stroma, representing a clear and continuous, high-signal arc-shaped linear structure, which was deeper in the central cornea than the para-central cornea. In contrast, a demarcation line, fuzzy and focally discontinuous, was visible only in a few patients in the TE-CXL group, with an almost uniform depth in the central and the para-central cornea. Confocal microscopy demonstrated an apparent mesh-like cross-linked collagen structure in the superficial and intermediate corneal stroma at all time points after surgery in the TG-CXL group, with thickening stromal collagen fibers and an increased number of interconnections. In contrast, the mesh-like structure and number of interconnections in the superficial corneal stroma were significantly reduced at 12 months after surgery in the TE-CXL group, with no cross-linking structure in the intermediate corneal stroma at any time point after surgery. No serious complications such as corneal infection, sterile corneal ulcer, and persistent epithelial defect were observed in both groups during the follow-up of 12 months. Conclusions: The TG-CXL procedure by sequential irradiation in two different diameters with ultraviolet A light was effective and safe in the management of progressive keratoconus in adults, achieving significant refractive improvement. This might be a good technical alternative for refractive corneal cross-linking surgery.

[Efficacy of deproteinized calf blood extract eye drops on early recovery after pterygium surgery].

Objective: To investigate the effect of deproteinized calf blood extract eye drops on early postoperative recovery in primary pterygium patients. Methods: This is a prospective randomized controlled study. Patients diagnosed with primary pterygium in single eye at affiliated Xiamen Eye Center of Xiamen University during March 2016 to May 2016 were enrolled. After Pterygium excision with autologous conjunctival transplantation, patients were randomly assigned into four groups by a random number table, treated with anti-inflammaroty drugs only (control group) or combined with the following agents: deproteinized calf blood extract eye drops (DCBE group), carboxymethylcellulose sodium eye drops (CMC group), and recombinant human epidermal growth factor eye drops (rEGF group). Short-form McGill pain questionnaire, slit lamp and corneal fluorescein sodium staining, non-contact intraocular pressure, uncorrected visual acuity (UCVA) and best corrected visual acquity (BCVA) as well as redness score of bulbar conjunctiva were performed before surgery (d0) and on day 1 (d1), day 2 (d2), day 3 (d3), day 7 (d7) and day 14 (d14) after surgery. Results: One hundred and fourteen patients including 43 males and 71 females, aged (48.9±12.5) years, were eventually included in this study. The McGill scores gradually decreased after surgery in all groups. On d2, the McGill score in DCBE group, control group, CMC group and rEGF group was (1.42±0.67), (2.21±0.88), (1.93±1.08) and (1.77±1.18), respectively; On d3, the score was (1.32±0.54), (1.93±0.72), (1.79±0.87) and (1.52±0.77), respectively. On d2 and d3, statistical difference was recorded among groups (d2, F=3.43, P=0.019; d3, F=4.047, P=0.009), and the McGill score of DCBE group was significantly lower than that of CMC group (d2, P=0.047, d3, P=0.017). On d2, the percentage of corneal epithelium defect in DCBE group, control group, CMC group and rEGF group was 8.6%±1.9%, 11.7%±1.7%, 11.5%±1.9% and 10.4%±1.8%, respectively; On d3, the percentage was 4.5%±2.2%, 9.2%±2.4%, 7.4%±2.5% and 5.9%±2.3%, respectively. On d2 and d3, statistical difference of corneal epithelium defect percentage was recorded among groups (d2, F=17.17, P<0.001; d3, F=21.4, P<0.001). On d2, the percentage of corneal epithelium defect in DCBE group was significantly lower than the other three groups (P<0.01); On d3, the percentage of corneal epithelium defect in DCBE group was significantly lower than control group and CMC group (P<0.001), while no difference was found between DCBE group and rEGF group (P>0.05). However, no statistical differences were recorded in the number of patients with vision improvement among the groups (P>0.05). The intraocular pressure remained stable. No differences in the conjunctival redness score were found among the groups after surgery (P>0.05). Conclusion: Our data demonstrated the efficacy of deproteinized calf blood extract eye drops on the postoperative management in patients with primary patients, with faster pain relief and promoted epithelium recovery. (Chin J Ophthalmol, 2019, 55:134-140).

[Accelerated transepithelial corneal collagen cross-linking for progressive keratoconus with a thin cornea: one-year results].

Objective: To evaluate the clinical results of keratoconic eyes with a thin cornea treated with accelerated transepithelial corneal collagen cross-linking (A-TE-CXL) within 1 year. Methods: Nineteen eyes of 19 patients with progressive keratoconus with a minimum corneal thickness from 380 µm to 420 µm (including the epithelium) were included in this prospective, nonrandomized clinical study and treated with A-TE-CXL. Scoring of pain and foreign body sensation, slit lamp examination, uncorrected visual acuity, best corrected distance visual acuity, corneal topography, anterior segment optical coherence tomography, in vivo corneal confocal microscopy and endothelial cell count were assessed before surgery and at 1, 3, 6 and 12 months postoperatively. Paired t test was applied for statistical analysis. Results: Mild pain and moderate foreign body sensation were reported by most patients within postoperative 24 hours, but rapidly disappeared on day 2. Extremely mild epithelial damage was observed within postoperative 24 hours, and the epithelium fully recovered on day 2. Improvement of visual acuity was recorded at 3 and 12 months. Pentacam corneal topography revealed a significant reduction of the thickness of the thinnest location from(395.2±13.8)µm preoperatively to (378.9±17.1)µm at 1 month postoperatively (t=2.982, P<0.01). Front curvature values were reduced postoperatively. K(MAX) was significantly decreased at 12 months (55.67±4.91) compared with (57.35±5.54) preoperatively, while K2 was also significantly decreased at 12 months (52.18±3.70) compared with (52.70±3.56) preoperatively (K(MAX), t=3.044, P<0.01. K2, t=2.384, P<0.05) . Within 1 month postoperatively, optical coherence tomography exhibited an increase of reflectance with a demarcation line in the anterior stroma. In vivo confocal microscopy also showed significant thickening and increased connections of collagen fibers with a maximal depth at about 90 to 120 µm. The corneal endothelial cell density remained stable (t=0.692, P>0.05). None of the patients showed postoperative complications such as corneal infection, scarring and ulceration. Conclusions: Within 1 year postoperatively, A-TE-CXL was effective and safe for the management of progressive keratoconus with a thin cornea. A-TE-CXL showed the advantages of very short time consuming in surgery, rapid recovery and very few complications, and had the potential to become a valid alternative for the treatment of keratoconus. (Chin J Ophthalmol, 2017, 53: 694-700).

Nanodiamond for biolabelling and toxicity evaluation in the zebrafish embryo in vivo.

Nanodiamond (ND) has been proposed for various biomedical applications, including bioimaging, biosensing and drug delivery, owing to its physical-chemical properties and biocompatibility. Particularly, ND has been demonstrated as fluorescence- and Raman-detectable labels in many cellular models. Different surface functionalization methods have been developed, varying the ND's surface properties and rendering the possibility to attach biomolecules to provide interaction with biological targets. For this, toxicity is of major concern in animal models. Aside from cellular models, a cost-effective animal test will greatly facilitate the development of applications. In this study, we use the rapid, sensitive and reproducible zebrafish embryo model for in vivo nanotoxicity test. We optimize the conditions for using this animal model and analyze the zebrafish embryonic development in the presence of ND. ND is observed in the embryo in vivo using laser confocal fluorescence microscopy and fluorescence lifetime imaging. Using the zebrafish model for a safety evaluation of ND-based nanolabel is discussed.

Critical fluctuations and the rates of interstate switching near the excitation threshold of a quantum parametric oscillator.

We study the dynamics of a nonlinear oscillator near the critical point where period-two vibrations are first excited with the increasing amplitude of parametric driving. Above the threshold, quantum fluctuations induce transitions between the period-two states over the quasienergy barrier. We find the effective quantum activation energies for such transitions and their scaling with the difference of the driving amplitude from its critical value. We also find the scaling of the fluctuation correlation time with the quantum noise parameters in the critical region near the threshold. The results are extended to oscillators with nonlinear friction.

Microwave down-conversion with an impedance-matched Λ system in driven circuit QED.

By driving a dispersively coupled qubit-resonator system, we realize an "impedance-matched" Λ system that has two identical radiative decay rates from the top level and interacts with a semi-infinite waveguide. It has been predicted that a photon input from the waveguide deterministically induces a Raman transition in the system and switches its electronic state. We confirm this through microwave response to a continuous probe field, observing near-perfect (99.7%) extinction of the reflection and highly efficient (74%) frequency down-conversion. These proof-of-principle results lead to deterministic quantum gates between material qubits and microwave photons and open the possibility for scalable quantum networks interconnected with waveguide photons.

Josephson parametric phase-locked oscillator and its application to dispersive readout of superconducting qubits.

The parametric phase-locked oscillator (PPLO) is a class of frequency-conversion device, originally based on a nonlinear element such as a ferrite ring, that served as a fundamental logic element for digital computers more than 50 years ago. Although it has long since been overtaken by the transistor, there have been numerous efforts more recently to realize PPLOs in different physical systems such as optical photons, trapped atoms, and electromechanical resonators. This renewed interest is based not only on the fundamental physics of nonlinear systems, but also on the realization of new, high-performance computing devices with unprecedented capabilities. Here we realize a PPLO with Josephson-junction circuitry and operate it as a sensitive phase detector. Using a PPLO, we demonstrate the demodulation of a weak binary phase-shift keying microwave signal of the order of a femtowatt. We apply PPLO to dispersive readout of a superconducting qubit, and achieved high-fidelity, single-shot and non-destructive readout with Rabi-oscillation contrast exceeding 90%.