Fermionic quantum processing with programmable neutral atom arrays.

Simulating the properties of many-body fermionic systems is an outstanding computational challenge relevant to material science, quantum chemistry, and particle physics.-5.4pc]Please note that the spelling of the following author names in the manuscript differs from the spelling provided in the article metadata: D. González-Cuadra, D. Bluvstein, M. Kalinowski, R. Kaubruegger, N. Maskara, P. Naldesi, T. V. Zache, A. M. Kaufman, M. D. Lukin, H. Pichler, B. Vermersch, Jun Ye, and P. Zoller. The spelling provided in the manuscript has been retained; please confirm. Although qubit-based quantum computers can potentially tackle this problem more efficiently than classical devices, encoding nonlocal fermionic statistics introduces an overhead in the required resources, limiting their applicability on near-term architectures. In this work, we present a fermionic quantum processor, where fermionic models are locally encoded in a fermionic register and simulated in a hardware-efficient manner using fermionic gates. We consider in particular fermionic atoms in programmable tweezer arrays and develop different protocols to implement nonlocal gates, guaranteeing Fermi statistics at the hardware level. We use this gate set, together with Rydberg-mediated interaction gates, to find efficient circuit decompositions for digital and variational quantum simulation algorithms, illustrated here for molecular energy estimation. Finally, we consider a combined fermion-qubit architecture, where both the motional and internal degrees of freedom of the atoms are harnessed to efficiently implement quantum phase estimation as well as to simulate lattice gauge theory dynamics.

Entangling two transportable neutral atoms via local spin exchange.

To advance quantum information science, physical systems are sought that meet the stringent requirements for creating and preserving quantum entanglement. In atomic physics, robust two-qubit entanglement is typically achieved by strong, long-range interactions in the form of either Coulomb interactions between ions or dipolar interactions between Rydberg atoms. Although such interactions allow fast quantum gates, the interacting atoms must overcome the associated coupling to the environment and cross-talk among qubits. Local interactions, such as those requiring substantial wavefunction overlap, can alleviate these detrimental effects; however, such interactions present a new challenge: to distribute entanglement, qubits must be transported, merged for interaction, and then isolated for storage and subsequent operations. Here we show how, using a mobile optical tweezer, it is possible to prepare and locally entangle two ultracold neutral atoms, and then separate them while preserving their entanglement. Ground-state neutral atom experiments have measured dynamics consistent with spin entanglement, and have detected entanglement with macroscopic observables; we are now able to demonstrate position-resolved two-particle coherence via application of a local gradient and parity measurements. This new entanglement-verification protocol could be applied to arbitrary spin-entangled states of spatially separated atoms. The local entangling operation is achieved via spin-exchange interactions, and quantum tunnelling is used to combine and separate atoms. These techniques provide a framework for dynamically entangling remote qubits via local operations within a large-scale quantum register.

Congestive heart failure with hypernatremia.

A patient presented with hypernatremia (plasma sodium level equals 171 mEq/L), marked congestive heart failure, and fluid retention. A high-salt intake and an inappropriate lack of thirst in this patient with poor cardiac function resulted in hypernatremia accompanied by edema. Hypertonic salt intake may have been due, in part, to zinc deficiency.

ANCA-associated vasculitis in Greek siblings with chronic exposure to silica.

We present the case of two siblings with similar environmental exposure to silica. Both of them developed perinuclear antineutrophil cytoplasmic antibody (p-ANCA)-associated vasculitis with pulmonary-renal syndrome. p-ANCAs were present with antimyeloperoxidase specificity on capture enzyme-linked immunosorbent assay. Treatment with corticosteroids and cyclophosphamide resulted in resolution of the clinical picture. Chronic exposure to silica is the leading environmental factor associated with ANCA-positive vasculitis. Several clusters of systemic vasculitis have been described. Positive and negative human leukocyte antigens (HLA) have been reported in systemic vasculitis. Affected brothers in our case shared one parental HLA haplotype. To the best of our knowledge, this is the first report of a family cluster of silica-induced, ANCA-associated systemic vasculitis with members sharing some of their HLA antigens.

Variation in energy expenditure among black-legged kittiwakes: effects of activity-specific metabolic rates and activity budgets.

We sought to determine the effect of variation in time-activity budgets (TABs) and foraging behavior on energy expenditure rates of parent black-legged kittiwakes (Rissa tridactyla). We quantified TABs using direct observations of radio-tagged adults and simultaneously measured field metabolic rates (FMR) of these same individuals (n=20) using the doubly labeled water technique. Estimated metabolic rates of kittiwakes attending their brood at the nest or loafing near the colony were similar (ca. 1.3 x basal metabolic rate [BMR]), although loafing during foraging trips was more costly (2.9 x BMR). Metabolic rates during commuting flight (7.3 x BMR) and prey-searching flight (6.2 x BMR) were similar, while metabolic rates during plunge diving were much higher (ca. 47 x BMR). The proportion of the measurement interval spent foraging had a positive effect on FMR (R2=0.68), while the combined proportion of time engaged in nest attendance and loafing near the colony had a negative effect on FMR (R2=0.72). Thus, more than two-thirds of the variation in kittiwake FMR could be explained by the allocation of time among various activities. The high energetic cost of plunge diving relative to straight flight and searching flight suggests that kittiwakes can optimize their foraging strategy under conditions of low food availability by commuting long distances to feed in areas where gross foraging efficiency is high.

Clinical experience with heat sterilization for reprocessing dialyzers.

Use of heat sterilization for dialysis reprocessing offers significant advantages over chemical germicides. Polysulfone dialyzers (Fresenius 60M or 80M) can be sterilized by heating to 105 degrees C for 20 hr, thus permitting clinical trials of this method. One hundred eighty patients received 9,000 treatments. Pyrogenic reactions, sepsis, and subjective symptoms have not occurred. In vitro clearances (Qb 500 ml/min, Qd 800 ml/min) at baseline and after 2-8 uses did not differ (340 +/- 29 vs. 352 +/- 4 ml/min, respectively). KoA determined in vivo did not decrease (baseline 709 +/- 131 vs. 7th use 632 +/- 50 ml/min). Kt/V for urea was not different in 18 patients treated with heat sterilized dialyzers over 6 months when compared with a baseline period with formaldehyde sterilized dialyzers (1.37 +/- 0.12 vs. 1.32 +/- 0.11 at similar time and blood flows). Mean use number was 7.4 (dialyzers limited to 11 uses). Of discarded dialyzers, 44% failed a bedside integrity test (blood side pressurized at > 400 mmHg for 1 min), 36% failed automated fiber bundle or pressure holding tests, 8% had a blood leak, and 12% reached 11 uses. Clinical blood leaks occur in < 0.5% of treatments. Heat sterilization is a safe and effective method of dialysis reprocessing, but quality control of the process is essential. Based on initial clinical experience, heat sterilization of dialyzers for reuse is a promising alternative to chemical disinfection.

In vivo verification of an automatic noninvasive system for real time Kt evaluation.

It is generally accepted that morbidity and mortality of hemodialysis patients is related to dialysis quantitation. Currently available methods for the quantitation of dialysis require blood sampling or a continuous measurement of changes in urea concentration during treatment. These maneuvers are time consuming and expensive, and are generally performed, at most, once per month. The authors introduce an on-line, automated method for measurement of dialyzer electrolyte clearance comparable to urea clearance by using dialysate conductivity sensors placed pre and post dialyzer, and measuring conductivity at three different pre dialyzer levels. Conditions that reduce clearance, such as recirculation or fiber clotting, are automatically taken into account so that the method measures effective clearance rather than dialyzer clearance. In vitro and in vivo studies validate the method. Results are immediately available and can be used to address problems such as improper needle placement and access recirculation. In addition, repetitive electrolyte clearance data can serve to enhance quality assurance programs with respect to verifying the function of reused or new dialyzers. Appropriate algorithms can be used to calculate delivered Kt/V.

Relative underestimation of fluid removal during hemodialysis hypotension measured by whole body bioimpedance.

Whole body bioimpedance is considered helpful in monitoring the removal of excess body water by ultrafiltration in hemodialysis patients. In this study, the cumulative, estimated decrease in extracellular volume (V(est)) modeled from whole body bioimpedance data was compared with measured volume (Vmeas) removed by ultrafiltration (UFR = 1.01 +/- 0.31 L/hr) in 12 patients during 36 high efficiency hemodialysis treatments. In the mean, estimated (V(est) = 3.0 +/- 1.4 L) and measured volumes (Vmeas = 3.4 +/- 1.1 L) correlated linearly: V(est) = 1.05 x Vmeas - 0.60, r2 = 0.68. Patients developed hypotension in half the treatments. Except for a larger decrease in systolic blood pressures in hypotensive (34 +/- 24 mmHg) vs. stable (14 +/- 15 mmHg) treatments, patient and treatment characteristics were not different between groups. However, at the end of hemodialysis, the difference V(est) - Vmeas was -0.8 +/- 0.9 L in hypotensive, and only 0.1 +/- 0.4 L in stable patients (p < 0.05). The difference between V(est) and Vmeas can be explained by a predominant removal of excess body water from central body compartments such as the trunk and the central blood volume during hypotension. These compartments are not adequately measured by whole body bioimpedance techniques. However, this information could be helpful in identifying patients with delayed peripheral fluid removal that may occur when either target weight is too low or UFR rates are too high.

Cardiopulmonary recirculation in dialysis. An underrecognized phenomenon.

Access recirculation can be determined by measuring blood temperature or blood water concentration in the dialyzer inlet after injecting a bolus of cold saline into the venous line. In patients with access recirculation, some of the cooled venous blood re-enters the blood inlet line soon after injection, resulting in a sharp transient drop in its temperature. There is also a prompt increase in blood water concentration at the dialyzer blood inlet caused by the dilution effect of the recirculated saline. In this study, data are reported on four patients studied under conditions where no access recirculation could occur because blood was returned to a second access or into a central vein. In these patients, transient cooling of the blood in the dialyzer inlet and a transient hemodilution after venous line injection of cold saline was still observed. These observations can be explained by passage of the injected saline through the heart and pulmonary blood vessels and return of a portion of the cooled blood to the vascular access, bypassing the systemic capillary microcirculation. This "cardiopulmonary recirculation" can cause dilution of urea in dialyzer inlet blood, with resulting errors in urea kinetic modeling and in computing access recirculation.

The role of fantasy in the treatment of a severely disturbed child.

This case study demonstrates the psychodynamic role of a system of fantasies that dominated the emotional life of a severely disturbed child. Transformations in these fantasies revealed her development of a more stable sense of reality and the capacity for object relations.

Two-particle quantum interference in tunnel-coupled optical tweezers.

The quantum statistics of atoms is typically observed in the behavior of an ensemble via macroscopic observables. However, quantum statistics modifies the behavior of even two particles. Here, we demonstrate near-complete control over all the internal and external degrees of freedom of two laser-cooled (87)Rb atoms trapped in two optical tweezers. This controllability allows us to observe signatures of indistinguishability via two-particle interference. Our work establishes laser-cooled atoms in optical tweezers as a promising route to bottom-up engineering of scalable, low-entropy quantum systems.

Real-time dynamics of single vortex lines and vortex dipoles in a Bose-Einstein condensate.

Understanding the behavior of quantized vortices is essential to gaining insight into diverse superfluid phenomena, from critical-current densities in superconductors to quantum turbulence in superfluids. We observe the real-time dynamics of quantized vortices in trapped dilute-gas Bose-Einstein condensates by repeatedly imaging the vortex cores. The precession frequency of a single vortex is measured by explicitly observing its time dependence and is found to be in good agreement with theory. We further characterize the dynamics of vortex dipoles in two distinct configurations: (i) an asymmetric configuration, in which the vortex trajectories are dynamic and nontrivial, and (ii) a stable, symmetric configuration, in which the dipole is stationary.

Complementary role of citrate and bicarbonate excretion in acid-base balance in the rat.

Studies were performed to evaluate whether alterations in the excretion of citrate, a metabolic precursor of bicarbonate, play a quantitatively important role in acid-base balance during bicarbonate feeding in the rat. Potassium depletion (K-DEPL), chloride depletion (Cl-DEPL), or potassium plus chloride depletion (KCl-DEPL) was produced by eliminating potassium, chloride, or potassium chloride from the diet. After 3 days of depletion, sodium bicarbonate (4,000 mueq/24 h) was added to the diet for 7 days. In all groups plasma bicarbonate concentration increased minimally during bicarbonate administration and was similar to normal controls receiving bicarbonate. In K-DEPL, citrate excretion was less than normal but bicarbonate excretion was greater than normal. In Cl-DEPL, bicarbonate excretion was less than normal but citrate excretion was greater than normal. In KCl-DEPL, bicarbonate and citrate excretion were similar to normal. Sodium bicarbonate was also administered to K-DEPL and KCl-DEPL rats in which plasma bicarbonate concentration averaged 32.9 meq/1. The reciprocal relationship between citrate and bicarbonate excretion was not altered by the profound metabolic alkalosis. Again, plasma bicarbonate concentration changed little with sodium bicarbonate administration. These studies suggest that the ability to excrete a base load remains intact despite potassium or chloride depletion or metabolic alkalosis. Complementary alterations of citrate and bicarbonate excretion play an important role in acid-base balance under these conditions.

Potassium-depletion alkalosis in the rat.

Studies were performed to investigate the role of concomitant chloride depletion in potassium-depletion alkalosis in the rat and the relationship between potassium depletion, plasma bicarbonate (PHCO3), and net acid excretion. 1) Selective potassium depletion (K-DEPL), potassium plus chloride depletion (KCl-DEPL), or selective chloride depletion (Cl-DEPL) was produced by administering a selectively potassium-, potassium and chloride-, or selectively chloride-deficient diet. In K-DEPL and KCl-DEPL rat, PHCO3 increased progressively and similarly during a 38-day period of restriction, whereas net acid excretion was similar and not elevated in either group. Cl-DEPL did not result in alkalosis. Chloride administration without potassium in alkalotic KCl-DEPL rats did not result in a sustained significant decrease in PHCO3. Potassium administration without chloride in alkalotic KCl-DEPL rats decreased PHCO3. Thus concomitant chloride depletion plays a minimal role in the alkalosis produced by dietary-induced potassium depletion. 2) Administration of a chronic acid load to alkalotic K-DEPL rats did not decrease PHCO3, and net acid excretion increased similarly as in normals. In K-DEPL rats after PHCO3 was reduced toward normal levels with acetazolamide, net acid excretion increased sharply above base-line values and PHCO3 increased markedly. Thus the alkalotic K-DEPL rat maintains the ability to excrete a chronic acid load, and a reduction in PHCO3 elicits an increase in acid excretion to restore the initial acid-base condition. These studies suggest that potassium depletion alters the set-point at which the kidney maintains PHCO3.

The effect of diuretics on systemic and renal hemodynamics in patients with renal insufficiency.

Diuretics have been used in acute renal failure in an attempt to increase urine flow and ameliorate the reduction in glomerular filtrate rate. A beneficial response occurs in some experimental models of acute renal failure when diuretics are administered prophylactically or very early in the course of renal failure and may require a renal vascular bed capable of responding partially, at least, to vasodilating stimuli. In chronic renal insufficiency the most important indications for diuretic use are for the treatment of systemic hypertension and for the correction of the congested state. However, the precise effect of diuretic therapy under these conditions is unpredictable and dependent on the functional state of the renal vessels. Diuretic administration may at times prove detrimental, resulting in a deterioration of glomerular filtration rate. In hemodynamically unstable conditions the slow removal of extracellular fluid by continuous arteriovenous hemofiltration may prove preferable to diuretic administration or standard forms of dialysis.

Intradialytic parenteral nutrition: a practical approach.

Intradialytic parenteral nutrition (IDPN) therapy is becoming more prevalent in the malnourished patient undergoing maintenance hemodialysis. This is of particular concern to the nephrology nurse in that additional time is required to administer the solution, monitor the patient, and document the process. The IDPN monitoring flowsheet described in this article was developed to promote continuity of care from treatment to treatment, especially during initiation of IDPN, and to assist the nephrology nurse in administering and monitoring the therapy.

Response to repeated frusemide administration on low chloride and low sodium intake in the rat.

In animals on a normal NaCl intake despite the repeated administration of a diuretic Cl and Na excretion return to baseline values after initial Cl and Na loss. In order to delineate whether this apparent resistance is consequent primarily on a decreased effect of the diuretic, or compensatory Cl and Na reabsorption when the diuretic is not acting, rats were injected with frusemide (1.5 mg twice a day intraperitoneally for 4 days) while on diets differing in Cl and Na content. On a normal NaCl diet Cl and Na excretion increased on day 1 and subsequently returned to baseline. On a low NaCl diet Cl and Na excretion remained above baseline on all 4 days, thereby demonstrating that frusemide continues to promote daily Cl and Na loss. On a low Cl-normal Na intake Na excretion returned to baseline after day 1, while Cl excretion remained above baseline on all 4 days. The increase in K and net acid excretion was highest in these studies. On a low Na-normal Cl intake Cl excretion returned to baseline after day 2, while Na excretion exceeded baseline on all 4 days. Daily K excretion increased least and net acid excretion decreased in these studies. Hourly data on all four diets indicate that frusemide always has an acute effect to promote both Cl and Na excretion. In the recovery period Cl or Na reabsorption is enhanced when the respective ion is available. The apparent resistance to daily frusemide administration on a normal NaCl intake is primarily consequent on enhanced reabsorption balancing the chloriuretic and natriuretic effects. Daily changes in K and net acid excretion are also determined, in part, by these opposing effects.

Role of citrate excretion in acid-base balance in diuretic-induced alkalosis in the rat.

Studies were performed to assess the role of changes in the excretion of citrate, a metabolic precursor of bicarbonate, in acid-base balance in diuretic-induced metabolic alkalosis. Rats on a low-chloride diet with sodium sulfate added were studied during a base-line period, 3 days of furosemide administration, and 4 days post-furosemide. During the period of furosemide administration, net acid excretion and plasma bicarbonate concentration increased. In the post-furosemide period, net acid excretion remained higher than base line but plasma bicarbonate concentration did not increase further. Citrate excretion was significantly higher in the post-furosemide period than in base line. Studies substituting sodium neutral phosphate or sodium bicarbonate for dietary sodium sulfate demonstrated greater increases in net acid excretion post-furosemide and, again, no increase in plasma bicarbonate concentration during this period. Citrate excretion was greater than in the sulfate group. The increment in citrate excretion was proportional to the base "load," defined with respect to changes in net acid excretion and/or dietary bicarbonate. Thus, in these studies alterations of base excretion in the form of citrate play an important role in acid-base balance during diuretic-induced metabolic alkalosis.