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An experiment demonstrating a link between classical single-flux quantum digital logic and a superconducting quantum circuit is reported. We implement coupling between a moving Josephson vortex (fluxon) and a flux qubit by reading out of a state of the flux qubit through a frequency shift of the fluxon oscillations in an annular Josephson junction. The energy spectrum of the flux qubit is measured using this technique. The implemented hybrid scheme opens an opportunity to readout quantum states of superconducting qubits with the classical fluxon logic circuits.

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Experiments towards realizing a readout of superconducting qubits by using ballistic Josephson vortices are reported. We measured the microwave radiation induced by a fluxon moving in an annular Josephson junction. By coupling a flux qubit as a current dipole to the annular junction, we detect periodic variations of the fluxon's oscillation frequency versus magnetic flux through the qubit. We found that the scattering of a fluxon on a current dipole can lead to the acceleration of a fluxon regardless of a dipole polarity. We use the perturbation theory and numerical simulations of the perturbed sine-Gordon equation to analyze our results. We are experimentally investigating a new type of detector that has been theoretically proposed for very fast and weakly perturbing readout of superconducting qubits [1,2]. The detection principle is based on measuring a delay time of a ballistic Josephson vortex (fluxon), moving in a Josephson transmission line (JTL) [3,4]. The vortex propagation delay depends on the state of the qubit magnetically coupled to the line. Expected advantages of this method are high time resolution and weak perturbation of the qubit. Potentially, the method might be suitable for implementing quantum feedback schemes [5,6] for flux qubits using on-chip fluxon readout. This approach also offers an opportunity to incorporate the existing single flux quantum logic (SFQ) solutions in the readout, bringing the dream about scalable quantum computer closer to reality [7,8].A Josephson vortex in underdamped JTL has properties of a relativistic particle carrying a magnetic flux quantum Φ 0 = h/2e [9].

We describe fabrication and testing of composite flux qubits combining Nb-and Al-based superconducting circuit technology. This hybrid approach to making qubits allows for employing π-phase shifters fabricated using well-established Nbbased technology of superconductor-ferromagnet-superconductor Josephson junctions. The important feature here is to obtain high interface transparency between Nb and Al layers without degrading sub-micron shadow mask. We achieve this by in-situ Ar etching using e-beam gun. Shadow-evaporated Al/AlO x /Al Josephson junctions with Nb bias pads show the expected current-voltage characteristics with reproducible critical currents. Using this technique, we fabricated composite Nb/Al flux qubits with Nb/CuNi/Nb π-shifters and measured their magnetic field response. The observed offset between the field responses of the qubits with and without πjunction is attributed to the π phase shift. The reported approach can be used for implementing a variety of hybrid Nb/Al superconducting quantum circuits.

In this paper, we examine the effect of increased wind penetration on system marginal prices (SMPs) in South Korea's electricity market. Korea's renewable portfolio standard (RPS) went into effect in 2012, with a goal of increasing the share of renewable generation to 10% of the total load by 2022. We examine the output of wind installations across the Korean peninsula and simulate an increase in wind penetration consistent with Korea's RPS targets. Under a variety of assumptions on demand elasticity, we find that higher shares of wind generation in total supply reduce both the average SMP and its variation. In particular, we find that wind energy output on the Korean peninsula is more correlated with peak electricity demand than has been reported for other regions. The per-unit value of wind energy to owners of wind assets is thus higher for South Korea than would be the case for European or North American locations with a similar mix of fuels other than wind.* Data for the remaining installations were not available for this analysis.† Given no growth in supply, growth in demand over time would lead to higher electricity prices, since the bid stack (electricity supply curve) becomes steeper at higher levels of supply. This would only magnify our calculated effects, since any displacement of the highest-cost generator would lead to a larger reduction in average generation costs. { See Section 4 for a qualitative discussion of how our results would be affected if we relax the assumption of fixed thermal generation mix.Effect of wind penetration on system prices in Korea's power markets A. Shcherbakova et al.