Hybridized solid-state qubit in the charge-flux regime

Most superconducting qubits operate in a regime dominated by either the electrical charge or the magnetic flux. Here we study an intermediate case: a hybridized charge-flux qubit with a third Josephson junction (JJ) added into the SQUID loop of the Cooper-pair box. This additional JJ allows the optimal design of a low-decoherence qubit. Both charge and flux $1/f$ noises are considered. Moreover, we show that an efficient quantum measurement of either the current or the charge can be achieved by using different area sizes for the third JJ.Comment: 7 pages, 5 figures. Phys. Rev. B, in pres

Fast generation of 3D deformable moving surfaces

Dynamic surface modeling is an important subject of geometric modeling due to their extensive applications in engineering design, entertainment and medical visualization. Many deformable objects in the real world are dynamic objects as their shapes change over time. Traditional geometric modeling methods are mainly concerned with static problems, therefore unsuitable for the representation of dynamic objects. Apart from the definition of a dynamic modeling problem, another key issue is how to solve the problem. Because of the complexity of the representations, currently the finite element method or finite difference method is usually used. Their major shortcoming is the excessive computational cost, hence not ideal for applications requiring real-time performance. We propose a representation of dynamic surface modeling with a set of fourth order dynamic partial differential equations (PDEs). To solve these dynamic PDEs accurately and efficiently, we also develop an effective resolution method. This method is further extended to achieve local deformation and produce n-sided patches. It is demonstrated that this new method is almost as fast and accurate as the analytical closed form resolution method and much more efficient and accurate than the numerical methods

Collocating Interface Objects: Zooming into Maps

May, Dean and Barnard [10] used a theoretically based model to argue that objects in a wide range of interfaces should be collocated following screen changes such as a zoom-in to detail. Many existing online maps do not follow this principle, but move a clicked point to the centre of the subsequent display, leaving the user looking at an unrelated location. This paper presents three experiments showing that collocating the point clicked on a map so that the detailed location appears in the place previously occupied by the overview location makes the map easier to use, reducing eye movements and interaction duration. We discuss the benefit of basing design principles on theoretical models so that they can be applied to novel situations, and so designers can infer when to use and not use them

Variable-frequency-controlled coupling in charge qubit circuits: Effects of microwave field on qubit-state readout

To implement quantum information processing, microwave fields are often used to manipulate superconuducting qubits. We study how the coupling between superconducting charge qubits can be controlled by variable-frequency magnetic fields. We also study the effects of the microwave fields on the readout of the charge-qubit states. The measurement of the charge-qubit states can be used to demonstrate the statistical properties of photons.Comment: 7 pages, 3 figure

Correlation-induced suppression of decoherence in capacitively coupled Cooper-pair boxes

Charge fluctuations from gate bias and background traps severely limit the performance of a charge qubit in a Cooper-pair box (CPB). Here we present an experimentally realizable method to control the decoherence effects of these charge fluctuations using two strongly capacitively coupled CPBs. This coupled-box system has a low-decoherence subspace of two states. Our results show that the inter-box Coulomb correlation can help significantly suppress decoherence of this two-level system, making it a promising candidate as a logical qubit, encoded using two CPBs.Comment: 5 pages, 2 figures. Phys. Rev. B, in pres