Demonstrating multi-round subsystem quantum error correction using matching and maximum likelihood decoders.

Quantum error correction offers a promising path for performing high fidelity quantum computations. Although fully fault-tolerant executions of algorithms remain unrealized, recent improvements in control electronics and quantum hardware enable increasingly advanced demonstrations of the necessary operations for error correction. Here, we perform quantum error correction on superconducting qubits connected in a heavy-hexagon lattice. We encode a logical qubit with distance three and perform several rounds of fault-tolerant syndrome measurements that allow for the correction of any single fault in the circuitry. Using real-time feedback, we reset syndrome and flag qubits conditionally after each syndrome extraction cycle. We report decoder dependent logical error, with average logical error per syndrome measurement in Z(X)-basis of ~0.040 (~0.088) and ~0.037 (~0.087) for matching and maximum likelihood decoders, respectively, on leakage post-selected data.

Comparison of Low-Dose Direct Acting Anticoagulant and Warfarin in patients Aged ≥80 years With Atrial Fibrillation.

Low dose direct acting oral anticoagulants (LDDOACS) were approved for elderly atrial Fibrillation (AF) patients with limited information. A retrospective analysis collecting baseline characteristics and outcomes in AF patients ≥ 80 prescribed LDDOAC or warfarin (W), from a multidisciplinary practice between 1/1/11 (First LDDOAC available) and 5/31/17 was conducted. From 9660 AF patients, 514 ≥ 80 received a LDDOAC and 422 W. A multivariable comparison found LDDOAC patients were older (p <0.001), had lower creatinine clearance (CrCl) (p = 0.006), used more anti-platelet drugs (p <0.001), and more often had new onset AF verses those prescribed W (p <0.001). There were no clinically significant differences among those patients receiving Dabigatran 75 mgs BID (D), Rivaroxaban 15mgs (R) or Apixaban 2.5mgs BID (A). Forty-eight and 50% of the patients remained on their LDDOAC or W for the observation period (p = 0.55). Stroke/systemic embolism (SSE) and CNS bleeds were 1.16 vs 2.22%/yr., (p = 0.143) and 1.46 vs 0.93%/yr., (p = 0.24). Mortality and major bleeds were 6.26 vs 1.67%/yr., and 12.3vs 3.77%/yr. (p <0.001). SSE were 1.1%/yr for D, R, and A (p = 0.94). CNS bleeds were 2.2 for D, 1.7 for R and 0.8%/yr. for A: p = 0.53. Major bleeding was: 14.3 for D, 14.1 for R and 9.1%/yr. for A, p = 0.048 (with A < R, p = 0.01). Mortality was 5.5 for D, 4.2 for R and 9.5% for A, p = 0.031. In conclusion, half the patients remained on their assigned anti-coagulant. SSE and intracranial bleed rates were similar and low. Major bleeds and deaths were different between groups emphasizing the need for prospective randomized trials in this growing population with AF.