Electric field distortions in structures of the twist bend nematic (NTB) phase of a bent-core liquid crystal

Dielectric spectroscopy of a twist bend nematic phase of an achiral bent core liquid crystalline compound under DC bias is used to investigate its response to electric field. Two collective relaxation processes are revealed, these are assigned to distortions of helicoidal structure by the external bias field. Frequency of the mode depends primarily on the helicoidal angle and has anomalous, softening- like behaviour at the nematic to the twist bend nematic transition. A coupling of dielectric anisotropy with electric field gives rise to a new equilibrium periodic structure in the time scale involved. The modulus of the wave vector gradually vanishes on increasing the bias field (except for the initial behaviour, which is just the opposite). Transition from the twist bend to the splay bend structure is clearly observed by a sudden drop in the frequency of this mode, which decreases almost linearly with increasing field. Results agree with predictions from current models for the periodically distorted a twist bend nematic phase.Comment: 14 PAGES, 7 FIGURES, submitted to Physical Review Letter

Randomized Benchmarking as Convolution: Fourier Analysis of Gate Dependent Errors

We provide an alternative proof of Wallman's [Quantum 2, 47 (2018)] and Proctor's [Phys. Rev. Lett. 119, 130502 (2017)] bounds on the effect of gate-dependent noise on randomized benchmarking (RB). Our primary insight is that a RB sequence is a convolution amenable to Fourier space analysis, and we adopt the mathematical framework of Fourier transforms of matrix-valued functions on groups established in recent work from Gowers and Hatami [Sbornik: Mathematics 208, 1784 (2017)]. We show explicitly that as long as our faulty gate-set is close to some representation of the Clifford group, an RB sequence is described by the exponential decay of a process that has exactly two eigenvalues close to one and the rest close to zero. This framework also allows us to construct a gauge in which the average gate-set error is a depolarizing channel parameterized by the RB decay rates, as well as a gauge which maximizes the fidelity with respect to the ideal gate-set

‘Freelance isn’t free.’ Coworking as a critical urban practice to cope with informality in creative labour markets

For more than a decade, co-working spaces have proliferated in cities worldwide. The paper discusses co-working as a critical urban practice because these spaces give support to the rising number of freelance workers in culture and creative industries. Freelance workers are an ‘invisible’ workforce whose impact often remains ‘hidden’ (Mould et al. 2014), who are not sufficiently protected through social welfare regulations and do not enjoy the same social entitlements as employed workers. This paper uses the concept of informality to highlight ongoing informalisation processes of employment relationships as well as informal working practices in creative labour markets. It discusses the emergence of co-working as a practice of collective self-help and self-organisation to cope with and to potentially overcome the informality, uncertainty and risks associated with independent work. It argues that co-working can be seen in line with other practices of informal urbanism that become more prevalent in European and North American cities due to the lack of affordable housing, the retrenchment of the social welfare state and the imposed conditions of ‘austerity urbanism’ (Peck 2012

Coworking in the city

In the aftermath of the financial and economic crisis of 2007 and 2008, a new type of collaboratively oriented workplace has emerged in cities. These coworking spaces and the associated practice of coworking exemplify new ways of organising labour in project-based and largely freelance occupations as found in the cultural and creative industries. But coworking spaces are not just flexible shared office spaces for creative professionals ‘working alone together’ (Spinuzzi, 2012). Coworking promotes a collective, community-based approach to the organisation of cultural and creative work where a particularly important role is accorded to the coworking host, whose activities are described as a curatorial practice aimed at creating a collaborative atmosphere and social relationships. Coworking spaces can therefore be regarded as a new form of urban social infrastructure enabling contacts and collaborations between people, ideas and connecting places

Generation and detection of NOON states in superconducting circuits

NOON states, states between two modes of light of the form $|N,0\rangle+e^{i\phi}|0,N\rangle$ allow for super-resolution interformetry. We show how NOON states can be efficiently produced in circuit quntum electrodynamics using superconducting phase qubits and resonators. We propose a protocol where only one interaction between the two modes is required, creating all the necessary entanglement at the start of the procedure. This protocol makes active use of the first three states of the phase qubits. Additionally, we show how to efficiently verify the success of such an experiment, even for large NOON states, using randomly sampled measurements and semidefinite programming techniques.Comment: 15 pages and 3 figure

Characterization of fibroblasts with a unique defect in processing antigens with disulfide bonds

A Chinese hamster ovary (CHO) fibroblast, transfected with murine major histocompatibility complex (MHC) class II genes, inefficiently simulated CD4+ Th cells specific for ovalbumin (OVA), hen egg lysozyme (HEL), and pork insulin which contains disulfide bonds. However, the fibroblasts elicited a T cell response to λ-repressor, which lacks disulfide bonds, and efficiently presented synthetic peptides. A somatic cell hybrid WALC, generated by fusing the hamster fibroblast with a murine L cell fibroblast, very efficiently processed OVA and HEL, suggesting that impaired processing was genetically complemented, suggesting that the processing defect is a recessive trait. Three distinct processing phenotypes were observed among twenty-eight hybrid clones analyzed for their ability to process a suboptimal concentration of OVA suggesting that a limited number of genes mediates the defect of WAB4 cells. The hamster fibroblasts were capable of processing two distinct denatured forms of OVA and carboxymethylated HEL either as effectively or more efficiently than a B lymphoma cell. The CHO cells also displayed diminished disulfide reduction of an endocytosed conjugate consisting of 125I-tyramine linked to poly-(D-lysine) through a disulfide spacer compared with that of the cell hybrid, providing direct evidence for defective reductive cleavage for the CHO cells. Diminished aspartic acid-mediated proteolysis of Ag could not account for the phenotype, because cell lysates and separated organelles from the fibroblast possessed higher acidic aspartyl proteolytic activity than lysates and organelles from a B lymphoma cell. The WAB4 cells had normal intracellular levels of cysteine, however they possessed diminished levels of intracellular glutathione (GSH). Buthionine sulfoximine (BSO) - mediated reduction of intracellular levels of GSH decreased the ability of the hybrid line WALC to process HEL. Conversely, treatment of WAB4 cells with N-acetyl cysteine increased their efficiency in the processing of HEl. These findings indicate that the intracellular level of GSH influences the capacity of cells to process antigens with the disulfide bonds. Thus, the antigen processing defect exhibited by transfected CHO cells is probably caused by their impaired ability to reduce disulfide bonds which may be related to the diminished intracellular GSH level