Quantum thermodynamics is emerging both as a topic of fundamental research and as means to understand and potentially improve the performance of quantum devices [1][2][3][4][5][6][7][8][9][10]. A prominent platform for achieving the necessary manipulation of quantum states is superconducting circuit quantum electrodynamics (QED) [11]. In this platform, thermalization of a quantum system [12][13][14][15] can be achieved by interfacing the circuit QED subsystem with a thermal reservoir of appropriate Hilbert dimensionality. Here we study heat transport through an assembly consisting of a superconducting qubit [16] capacitively coupled between two nominally identical coplanar waveguide resonators, each equipped with a heat reservoir in the form of a normal-metal mesoscopic resistor termination. We report the observation of tunable photonic heat transport through the resonator-qubit-resonator assembly, showing that the reservoir-to-reservoir heat flux depends on the interplay between the qubit-resonator and the resonator-reservoir couplings, yielding qualitatively dissimilar results in different coupling regimes. Our quantum heat valve is relevant for the realisation of quantum heat engines [17] and refrigerators, that can be obtained, for example, by exploiting the time-domain dynamics and coherence of driven superconducting qubits [18,19]. This effort would ultimately bridge the gap between the fields of quantum information and thermodynamics of mesoscopic systems. * alberto.ronzani@aalto.fi arXiv:1801.09312v3 [cond-mat.mes-hall]

We report the design and implementation of a high-performance superconducting quantum-interference proximity transistor based on aluminum-copper technology. With the adoption of a thin and short copper nanowire, we demonstrate full phase-driven modulation of the proximity-induced minigap in the normalmetal density of states. Under optimal bias, we record unprecedentedly high flux-to-voltage (up to 3 mV=Φ 0 ) and flux-to-current (exceeding 100 nA=Φ 0 ) transfer function values at subkelvin temperatures, where Φ 0 is the flux quantum. The best magnetic-flux resolution (as low as 500nΦ 0 = ffiffiffiffiffiffi Hz p at 240 mK being limited by the room-temperature preamplification stage) is reached under fixed current bias. These figures of merit combined with ultralow power dissipation and micrometer-size dimensions make this mesoscopic interferometer attractive for low-temperature applications such as the investigation of the magnetization of small spin populations.

The minimum-energy geometrical structure of the regioregular head-to-tail poly(3-hexylthiophene) (rr-HT-P3HT) polymer has been addressed by means of density functional theory (DFT) calculations which include long-range (van der Waals) interactions. The problem of the P3HT structure has been debated in the literature in the last decades mainly for what concerns the arrangement of the alkyl side chains of the polymer and the type and content of the crystalline primitive cell. The main result of our calculations is that the energetically favored structure of the crystalline polymer at T = 0 K corresponds to polythiophene chains with slightly (∼16°) non co-planar rings and a fishbone arrangement of tilted alkyl side chains with complex internal structure. The alkyl side chains are negligibly interdigitated with those of the adjacent polymer layers; moreover the five terminal carbon atoms of each alkyl side chain are co-planar in all-trans staggered conformation. The optimized geometrical structure obtained for the rr-HT-P3HT polymer is in agreement with measured X-ray spectra of high molecular weight P3HT crystalline samples, and confirms that two non-equivalent polymer chains, mutually shifted along the backbone axis, are contained in an orthorhombic primitive cell

We consider properties of a fully superconducting variant of the superconducting quantum interference proximity transistor, a magnetic flux sensor. We study the density of states in a finite-size superconducting metal wire in the diffusive limit, and how it depends on the phase gradient of the order parameter. We describe the dependence on the junction length and interface transparency, and discuss properties relevant for using the structure in magnetic flux detection applications. arXiv:1607.04414v2 [cond-mat.supr-con]