Spin squeezed GKP codes for quantum error correction in atomic ensembles

GKP codes encode a qubit in displaced phase space combs of a continuous-variable (CV) quantum system and are useful for correcting a variety of high-weight photonic errors. Here we propose atomic ensemble analogues of the single-mode CV GKP code by using the quantum central limit theorem to pull back the phase space structure of a CV system to the compact phase space of a quantum spin system. We study the optimal recovery performance of these codes under error channels described by stochastic relaxation and isotropic ballistic dephasing processes using the diversity combining approach for calculating channel fidelity. We find that the spin GKP codes outperform other spin system codes such as cat codes or binomial codes. Our spin GKP codes based on the two-axis countertwisting interaction and superpositions of SU(2) coherent states are direct spin analogues of the finite-energy CV GKP codes, whereas our codes based on one-axis twisting do not yet have well-studied CV analogues. An implementation of the spin GKP codes is proposed which uses the linear combination of unitaries method, applicable to both the CV and spin GKP settings. Finally, we discuss a fault-tolerant approximate gate set for quantum computing with spin GKP-encoded qubits, obtained by translating gates from the CV GKP setting using quantum central limit theorem.Comment: More details added to the previous versions with more figure

The Case Against Chevron Deference in Immigration Adjudication

The Duke Law Journal’s fifty-first annual administrative law symposium examines the future of Chevron deference—the command that a reviewing court defer to an agency’s reasonable interpretation of an ambiguous statute the agency administers. In the lead article, Professors Kristin Hickman and Aaron Nielson argue that the Supreme Court should narrow Chevron ’s domain to exclude interpretations made via administrative adjudication. Building on their framing, this Article presents an in-depth case study of immigration adjudication and argues that this case against Chevron has perhaps its greatest force when it comes to immigration. That is because much of Chevron ’s theory for congressional delegation and judicial deference—including agency expertise, deliberative process, and even political accountability—collapses in the immigration adjudication context. As for potential reform, Professors Hickman and Nielson understandably focus on the Supreme Court. This Article also explores that judicial option but argues that it is a mistake to focus just on courts when it comes to immigration law and policy. The political branches can and should act to narrow Chevron ’s domain. First, this proposal should be part of any comprehensive immigration reform legislation. Second, the Executive Branch can and should embrace this reform internally—by not seeking Chevron deference in immigration adjudication and by turning to rulemaking instead of adjudication to make major immigration policy. Shifting the immigration policymaking default from adjudication to rulemaking is more consistent with Chevron ’s theoretical foundations—to leverage agency expertise, to engage in a deliberative process, and to increase political accountability

The Case Against Chevron Deference in Immigration Adjudication

The Duke Law Journal’s fifty-first annual administrative law symposium examines the future of Chevron deference—the command that a reviewing court defer to an agency’s reasonable interpretation of an ambiguous statute the agency administers. In the lead article, Professors Kristin Hickman and Aaron Nielson argue that the Supreme Court should narrow Chevron ’s domain to exclude interpretations made via administrative adjudication. Building on their framing, this Article presents an in-depth case study of immigration adjudication and argues that this case against Chevron has perhaps its greatest force when it comes to immigration. That is because much of Chevron ’s theory for congressional delegation and judicial deference—including agency expertise, deliberative process, and even political accountability—collapses in the immigration adjudication context. As for potential reform, Professors Hickman and Nielson understandably focus on the Supreme Court. This Article also explores that judicial option but argues that it is a mistake to focus just on courts when it comes to immigration law and policy. The political branches can and should act to narrow Chevron ’s domain. First, this proposal should be part of any comprehensive immigration reform legislation. Second, the Executive Branch can and should embrace this reform internally—by not seeking Chevron deference in immigration adjudication and by turning to rulemaking instead of adjudication to make major immigration policy. Shifting the immigration policymaking default from adjudication to rulemaking is more consistent with Chevron ’s theoretical foundations—to leverage agency expertise, to engage in a deliberative process, and to increase political accountability

Detection of Early Loss of Color Vision in Age-Related Macular Degeneration - With Emphasis on Drusen and Reticular Pseudodrusen

Purpose: To evaluate chromatic sensitivity in patients with age-related macular degeneration (AMD) characterized by drusen and reticular pseudodrusen. To investigate whether the severity of color vision loss can distinguish between various stages of AMD and hence be used as an index of progression toward advanced AMD. Methods: Chromatic sensitivity was measured by using the Color Assessment and Diagnosis (CAD) test in asymptomatic individuals with early and intermediate AMD and compared to normative data. All study participants had logMAR visual acuity of 0.3 or better. The CAD thresholds measured in eyes with and without reticular pseudodrusen were also compared and related to central macular thickness (CMT). Student's t-test P values < 0.05 were considered significant. Results: All early- and intermediate-AMD eyes (n = 90) had chromatic sensitivity loss in either RG (red/green) or YB (yellow/blue), or both (P < 0.0001) as compared to age-matched normal subjects. The eyes exhibited a range of CAD thresholds affecting both color mechanisms, but YB color thresholds were in general higher than RG thresholds (P < 0.001). Intermediate-AMD patients exhibited large intersubject variability. In general, eyes with reticular pseudodrusen and eyes with CMT < 200 μm had significantly higher CAD thresholds. Conclusions: The anatomic integrity of cone photoreceptors remains relatively unaffected in early and intermediate stages of AMD. The processing of cone signals in the retina can, however, be heavily disrupted with subsequent loss of both YB and RG chromatic sensitivity. The greatest losses were observed in eyes with reticular pseudodrusen

APC/C – the master controller of origin licensing?

DNA replication must be tightly controlled to prevent initiation of a second round of replication until mitosis is complete. So far, components of the pre-replicative complex (Cdt1, Cdc6 and geminin) were considered key players in this regulation. In a new study, Machida and Dutta have shown that depletion of Emi1 caused cells to replicate their DNA more than once per cell cycle [1]. This effect was dependent on the ability of Emi1 to inhibit the APC/C. In addition to its role in regulating entry into mitosis, oscillation of APC/C activity regulates pre-RC formation: high APC/C activity in late M/G1 allows pre-RC formation and low APC/C activity in S/G2 prevents pre-RC formation for a second time thereby preventing rereplication. Each redundant pathway to prevent rereplication is dependent on regulating one of the pre-RC components, and all of the pathways are co-regulated by Emi1 through the APC/C. In this commentary we discuss how this new role of Emi1 adds to our understanding of the regulation of replication initiation. We also review the literature to analyze whether APC/C has a role in regulating endoreduplication (a normal state of polyploidy in some differentiated cells). Similarly a role of premature APC/C activation in genomic instability of tumors is discussed

Acuity and colour vision changes post intravitreal dexamethasone implant injection in patients with diabetic macular oedema

Purpose To evaluate changes in colour vision following intravitreal injection of Dexamethasone implant (Ozurdex) in patients with diabetic macular oedema (DMO). Both red-green (RG) and yellow-blue (YB) chromatic sensitivity were assessed using the Colour Assessment & Diagnosis (CAD) test which isolates the use of colour signals and provides age-corrected, statistical limits for normal trichromats. To determine whether colour changes and visual acuity (VA) post-treatment relate to central sub-field retinal thickness (CST). Methods Fourteen patients with DMO who were undergoing treatment with Ozurdex were recruited for this study. RG and YB colour thresholds were measured using the CAD test, best corrected visual acuity was assessed using the ETDRS chart and CST was measured using spectral domain optical coherence tomography (SD-OCT). All tests were performed monocularly at baseline and 24 weeks post injection. Results All patients (n = 14 eyes), had significant loss of RG and YB chromatic sensitivity at baseline (p<0.05). The mean age was 56 ± 9.5 years. The age specific, monocular, upper normal limits for a 56 year old subject are 2.66 for RG and 2.85 for YB. In this study, the measured, pre injection thresholds (mean±SD) were 22.6 ± 11.3 for RG and 16.2 ± 3.76 for YB. There was significant improvement in RG threshold post injection (i.e., 19.2 ± 10.8 (p<0.05)). No significant changes were found in the YB thresholds with corresponding mean and range values of: 15.8 ± 4.6 (p = 0.23). CST pre-treatment was 542 ±135 μm. After treatment and by week 24 the CST values decreased to 435 ±127 μm. Conclusions RG colour thresholds provide a sensitive measure of functional change in diabetic subjects with macular oedema. The YB system is damaged severely in the DMO patients studied and shows little or no recovery post treatment. The improvement in VA and particularly in RG colour vision correlate well with the measured decrease in CST. The results suggest that the improvement in the RG chromatic sensitivity can provide a useful biomarker for monitoring the efficacy of treatment in DMO

Quantum Optimal Control of Nuclear Spin Qudecimals in 87Sr^{87}\text{Sr}

We study the ability to implement unitary maps on states of the $I=9/2$ nuclear spin in \textsuperscript{87}Sr, a $d=10$ dimensional (qudecimal) Hilbert space, using quantum optimal control. Through a combination of nuclear spin-resonance and a tensor AC-Stark shift, by solely modulating the phase of a radio-frequency magnetic field, the system is quantum controllable. Alkaline earth atoms, such as \textsuperscript{87}Sr, have a very favorable figure-of-merit for such control due to narrow intercombination lines and the large hyperfine splitting in the excited states. We numerically study the quantum speed-limit, optimal parameters, and the fidelity of arbitrary state preparation and full SU(10) maps, including the presence of decoherence due to optical pumping induced by the light-shifting laser. We also study the use of robust control to mitigate some dephasing due to inhomogeneities in the light shift. We find that with an rf-Rabi frequency of $\Omega_\text{rf}$ and 0.5\% inhomogeneity in the the light shift we can prepare an arbitrary Haar-random state in a time $T={4.5}\pi/\Omega_\text{rf}$ with average fidelity $\langle \mathcal{F}_\psi \rangle =0.9992$, and an arbitrary Haar-random SU(10) map in a time $T=24\pi/\Omega_\text{rf}$ with average fidelity $\langle \mathcal{F}_U \rangle = 0.9923$

Evaluation of real-world early response of DMO to aflibercept therapy to inform future clinical trial design of novel investigational agents

New clinical trials for diabetic macular oedema (DMO) are being designed to prove superiority over aflibercept when this agent is already very effective in improving visual acuity (VA) and DMO. The aim of this study was to determine the optimal inclusion–exclusion criteria for trials to aim for superiority in visual outcomes with newer agents. As Phase 1 studies are short duration, we aimed to evaluate the early response of aflibercept in a real-world cohort initiated on monthly aflibercept for 3 consecutive injections and observed the effects at 4 months. The sub-optimal responders were pre-defined based on different cut-offs for VA and central sub-field thickness (CST). 200 patients with treatment naïve DMO treated with 3 loading doses of aflibercept were included in the study. We found that those presenting with baseline VA of 35–54 ETDRS letters (n = 43) had higher proportion of sub-optimal responders compared to other categories (p < 0.001). Patients with baseline CST of less than 400 µm (n = 96) responded less well functionally and anatomically to loading dose than eyes with baseline CST of 400 µm or more (n = 104, p = 0.02), indicating that eyes with CST ≥ 400 µm is another inclusion criteria. There was minimal correlation between change in CST and change in VA at 4 months (r = − 0.27), suggesting that both these inclusion criteria are non-exclusive. However, for maximal efficacy, patients that meet both these inclusion criteria are more likely to show benefit from an alternative intervention. New trials should aim to include patients with treatment naïve DMO with VA between 35–54 letters and CST of 400 µm or more when aflibercept is used as the comparator

Qudit entanglers using quantum optimal control

We study the generation of two-qudit entangling quantum logic gates using two techniques in quantum optimal control. We take advantage of both continuous, Lie-algebraic control and digital, Lie-group control. In both cases, the key is access to a time-dependent Hamiltonian which can generate an arbitrary unitary matrix in the group SU($d^2$). We find efficient protocols for creating high-fidelity entangling gates. As a test of our theory, we study the case of qudits robustly encoded in nuclear spins of alkaline earth atoms and manipulated with magnetic and optical fields, with entangling interactions arising from the well-known Rydberg blockade. We applied this in a case study based on a $d=10$ dimensional qudit encoded in the $I=9/2$ nuclear spin in $^{87}$Sr, controlled through a combination of nuclear spin-resonance, a tensor AC-Stark shift, and Rydberg dressing, which allows us to generate an arbitrary symmetric entangling two-qudit gate such as CPhase. Our techniques can be used to implement qudit entangling gates for any $2\le d \le10$ encoded in the nuclear spin. We also studied how decoherence due to the finite lifetime of the Rydberg states affects the creation of the CPhase gate and found, through numerical optimization, a fidelity of $0.9985$, $0.9980$, $0.9942$, and $0.9800$ for $d=2$, $d=3$, $d=5$, and $d=7$ respectively. This provides a powerful platform to explore the various applications of quantum information processing of qudits including metrological enhancement with qudits, quantum simulation, universal quantum computation, and quantum error correction.Comment: Included more details and figure

Chromatic sensitivity changes in Type I and Type II diabetics

Purpose: Previous studies have shown that patients with type I diabetes can exhibit significant loss of colour vision that often precedes any clinical signs of retinopathy. In this study we investigated loss of red-green (RG) and yellow-blue (YB) chromatic sensitivity in both type I and type II diabetic patients. The aim was to establish how the type, onset, retinal thickness and the glycated haemoglobin (HbA1c) level affect the severity of RG and YB loss. Methods: 110 patients diagnosed with diabetes (90 type II and 20 type I) took part in this study. BCVA, duration of diabetes, HbA1c and central subfield thickness (CST) were recorded in each patient. RG and YB colour thresholds were measured monocularly using the CAD (Colour Assessment & Diagnosis) test (Expert Rev. Ophthalmol. 6:409-420, 2011). Results: Both type I and II diabetic patients showed significant loss of both RG and YB chromatic sensitivity with thresholds that ranged from just above the upper, age-corrected threshold limits for normal colour vision to complete absence of chromatic sensitivity. There was little or no correlation with type, duration of diabetes, loss of visual acuity, retinal thickness changes or the HbA1C index. The diabetics examined separated into two groups, the majority have RG (72%) and YB (65%) thresholds below ~ 6 standard normal CAD units with little or no difference between type I and II. A subgroup of patients (mostly type II) exhibit much larger thresholds, but no correlation with age or duration of diabetes. Conclusions: RG and YB colour thresholds provide a sensitive measure of functional change in diabetics. Both type I and II diabetic patients exhibit loss of both RG and YB chromatic sensitivity, with little or no difference between the two types. Neural changes in diabetes that cause loss of colour vision do not appear to be linked directly to type, duration or the HbA1c level