Embedded quantum-error correction and controlled-phase gate for molecular spin qubits

A scalable architecture for quantum computing requires logical units supporting quantum-error correction. In this respect, magnetic molecules are particularly promising, since they allow one to define logical qubits with embedded quantum-error correction by exploiting multiple energy levels of a single molecule. The single-object nature of this encoding is expected to facilitate the implementation of error correction procedures and logical operations. In this work, we make progress in this direction by showing how two-qubit gates between error-protected units can be realised, by means of easily implementable sequences of electro-magnetic pulses

Molecular Nanomagnets as Qubits with Embedded Quantum-Error Correction

We show that molecular nanomagnets have a potential advantage in the crucial rush toward quantum computers. Indeed, the sizable number of accessible low-energy states of these systems can be exploited to define qubits with embedded quantum error correction. We derive the scheme to achieve this crucial objective and the corresponding sequence of microwave/radiofrequency pulses needed for the error correction procedure. The effectiveness of our approach is shown already with a minimal S = 3/2 unit corresponding to an existing molecule, and the scaling to larger spin systems is quantitatively analyzed

Ultrafast Transient Infrared Spectroscopy of Photoreceptors with Polarizable QM/MM Dynamics

Ultrafast transient infrared (TRIR) spectroscopy is widely used to measure the excitation-induced structural changes of protein-bound chromophores. Here, we design a novel and general strategy to compute TRIR spectra of photoreceptors by combining μs-long MM molecular dynamics with ps-long QM/AMOEBA Born-Oppenheimer molecular dynamics (BOMD) trajectories for both ground and excited electronic states. As a proof of concept, the strategy is here applied to AppA, a blue-light-utilizing flavin (BLUF) protein, found in bacteria. We first analyzed the short-time evolution of the embedded flavin upon excitation revealing that its dynamic Stokes shift is ultrafast and mainly driven by the internal reorganization of the chromophore. A different normal-mode representation was needed to describe ground- and excited-state IR spectra. In this way, we could assign all of the bands observed in the measured transient spectrum. In particular, we could characterize the flavin isoalloxazine-ring region of the spectrum, for which a full and clear description was missing

Discovery of Griffiths phase in itinerant magnetic semiconductor Fe_{1-x}Co_xS_2

Critical points that can be suppressed to zero temperature are interesting because quantum fluctuations have been shown to dramatically alter electron gas properties. Here, the metal formed by Co doping the paramagnetic insulator FeS$_2$, Fe$_{1-x}$Co$_x$S$_2$, is demonstrated to order ferromagnetically at $x>x_c=0.01\pm0.005$ where we observe unusual transport, magnetic, and thermodynamic properties. We show that this magnetic semiconductor undergoes a percolative magnetic transition with distinct similarities to the Griffiths phase, including singular behavior at $x_c$ and zero temperature.Comment: 10 pages, 4 figure

Magnetic and thermodynamic properties of cobalt doped iron pyrite: Griffiths Phase in a magnetic semiconductor

Doping of the band insulator FeS$_2$ with Co on the Fe site introduces a small density of itinerant carriers and magnetic moments. The lattice constant, AC and DC magnetic susceptibility, magnetization, and specific heat have been measured over the $0\le x\le 0.085$ range of Co concentration. The variation of the AC susceptibility with hydrostatic pressure has also been measured in a small number of our samples. All of these quantities show systematic variation with $x$ including a paramagnetic to disordered ferromagnetic transition at $x=0.007\pm 0.002$. A detailed analysis of the changes with temperature and magnetic field reveal small power law dependencies at low temperatures for samples near the critical concentration for magnetism, and just above the Curie temperature at higher $x$. In addition, the magnetic susceptibility and specific heat are non-analytic around H=0 displaying an extraordinarily sharp field dependence in this same temperature range. We interpret this behavior as due to the formation of Griffiths phases that result from the quenched disorder inherent in a doped semiconductor.Comment: 22 pages including 27 figure

Azathioprine for prevention of clinical recurrence in Crohn's disease patients with severe endoscopic recurrence: an IG-IBD randomized double-blind trial

The recurrence of Crohn's Disease after ileo-colonic resection is a crucial issue. Severe endoscopic lesions increase the risk of developing early symptoms. Prevention and treatment of post-operative Endoscopic Recurrence (ER) have been studied with conflicting results. We compare effi cacy of azathioprine (AZA) vs. high-dose 5-aminosalicylic acid (5-ASA) in preventing clinical recurrence and treating severe post-operative ER

TM6SF2 rs58542926 is not associated with steatosis and fibrosis in largecohort of patients with genotype 1 chronic hepatitis C

Background & Aims: We tested the putative association of the rs58542926 variant of TM6SF2, a recently described genetic determinant of nonalcoholic fatty liver disease, with steatosis and fibrosis in genotype 1(G1) chronic hepatitis C(CHC) patients. Methods: A total of 694 consecutively biopsied Caucasian G1 CHC patients were genotyped for TM6SF2 rs58542926, IL28B rs12979860 and PNPLA3 rs738409. Steatosis was classified as absent (<5%), mild-moderate(5-29%) and severe( 6530%), Fibrosis was considered severe if=F3-F4. Results: Carriers of TM6SF2 rs58542926 (6.3% of patients) exhibited lower serum levels of cholesterol (P=0.04) and triglycerides (P=0.01), but a similar distribution of steatosis severity (P=0.63), compared to noncarriers. Prevalence and severity of steatosis were reduced in IL28B C allele carriers (P=0.005) and elevated in PNPLA3G allele carriers (P<0.001). After adjustment for age, gender, body mass index and homoeostasis model assessment score, steatosis severity was independently associated with IL28B rs12979860 (odds ratio [OR] 0.69, 95% confidence interval [CI] 0.55-0.86, P=0.001) and PNPLA3 rs738409 (OR 1.84, 95% CI 1.46-2.83, P<0.001), but not TM6SF2 rs58542926 (OR 1.48, 95% CI 0.82-2.69, P=0.19). Variants of TM6SF2 (30.9% vs. 25%, P=0.40), IL28B and PNPLA3 were not directly associated with fibrosis severity, although variants of IL28B and PNPLA3 promoted steatosis (OR 1.36, 95% CI 1.06-1.75, P=0.01) that in turn is associated with severe fibrosis. Conclusions: In G1 CHC patients, TM6SF2 rs58542926 does not affect the histological severity of liver damage. However, IL28B rs12979860 and PNPLA3 rs738409 modify steatosis