Universal set of Dynamically Protected Gates for Bipartite Qubit Networks II: Soft Pulse Implementation of the [[5,1,3]] Quantum Error Correcting Code

We model repetitive quantum error correction (QEC) with the single-error-correcting five-qubit code on a network of individually-controlled qubits with always-on Ising couplings, using our previously designed universal set of quantum gates based on sequences of shaped decoupling pulses. In addition to serving as accurate quantum gates, the sequences also provide dynamical decoupling (DD) of low-frequency phase noise. The simulation involves integrating unitary dynamics of six qubits over the duration of tens of thousands of control pulses, using classical stochastic phase noise as a source of decoherence. The combined DD/QEC protocol dramatically improves the coherence, with the QEC alone responsible for more than an order of magnitude infidelity reduction.Comment: 12 pages, 9 figure

Regular dependence of acoustic signals from dispersion at jet grinding ores

В умовах роботи струминних подрібнювальних установок виявлено акустичні закономірності зміни дисперсності матеріалів у процесі тонкого подрібнення. Запропоновано комплексні акустичні й технологічні критерії підвищення якості подрібненого продукту при зниженні питомих енерговитратВ условиях работы струйных измельчительных установок выявлены акустические закономерности изменения дисперсности материалов в процессе тонкого измельчения. Предложены комплексные акустические и технологические критерии повышения качества измельченного продукта при снижении удельных энергозатрат.In operating conditions of jet grinding installations acoustic laws of material dispersiveness change are revealed during thin grinding. Complex acoustic and technological criteria of ground product quality improvement are offered with specific power inputs decrease

Fault-Tolerance of "Bad" Quantum Low-Density Parity Check Codes

We discuss error-correction properties for families of quantum low-density parity check (LDPC) codes with relative distance that tends to zero in the limit of large blocklength. In particular, we show that any family of LDPC codes, quantum or classical, where distance scales as a positive power of the block length, $d \propto n^\alpha$, $\alpha>0$, can correct all errors with certainty if the error rate per (qu)bit is sufficiently small. We specifically analyze the case of LDPC version of the quantum hypergraph-product codes recently suggested by Tillich and Z\'emor. These codes are a finite-rate generalization of the toric codes, and, for sufficiently large quantum computers, offer an advantage over the toric codes.Comment: 4.5 pages, 1 figur

Spin glass reflection of the decoding transition for quantum error correcting codes

We study the decoding transition for quantum error correcting codes with the help of a mapping to random-bond Wegner spin models. Families of quantum low density parity-check (LDPC) codes with a finite decoding threshold lead to both known models (e.g., random bond Ising and random plaquette $\Z2$ gauge models) as well as unexplored earlier generally non-local disordered spin models with non-trivial phase diagrams. The decoding transition corresponds to a transition from the ordered phase by proliferation of extended defects which generalize the notion of domain walls to non-local spin models. In recently discovered quantum LDPC code families with finite rates the number of distinct classes of such extended defects is exponentially large, corresponding to extensive ground state entropy of these codes. Here, the transition can be driven by the entropy of the extended defects, a mechanism distinct from that in the local spin models where the number of defect types (domain walls) is always finite.Comment: 15 pages, 2 figure

Limited operating conditions of the jet mill injector

Наведено три критичні режими роботи інжектору струминного млина та показано умови їх виникнення. Знайдено коефіцієнти інжекції щодо розглянутих критичних режимів.Представлены три критических режима работы инжектора струйной мельницы и показаны условия их возникновения. Найдены коэффициента инжекции, соответствующие рассмотренным критическим режимам.Представлены три критических режима работы инжектора струйной мельницы и показаны условия их возникновения. Найдены коэффициента инжекции, соответствующие рассмотренным критическим режимам