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Nanosilicon for quantum information
Published in Klaus D. Sattler, Silicon Nanomaterials Sourcebook, 2017
In a charge qubit the two-qubit states are defined in a double quantum dot by a single electron charge occupying either the first or the second dot (Hayashi et al. 2003; Petersson et al. 2010; Kim et al. 2015; Cao et al. 2013). Quantum dot potential wells and the interdot tunneling barrier are electrostatically defined by means of metal gates. Coherent qubit rotations can be achieved by controlling the bias between the dots and interdot tunnel coupling as described in Figure 29.9. Qubit dynamics is extremely fast, leading to the potential for 10 GHz frequency operation and to the concurrent drawback of very fast dephasing (ns timescale) induced by electrical noise.
Physically Defined Coupled Silicon Quantum Dots Containing a Few Electrons for Electron Spin Qubits
Published in Simon Deleonibus, Emerging Devices for Low-Power and High-Performance Nanosystems, 2018
Tetsuo Kodera, Kosuke Horibe, Shunri Oda
One example of a charge qubit is a single electron confined in a tunnel-coupled double quantum dot (DQD), in which we use the superposition of the probability of presence of the single electron in each QD. Charge qubit operation has been achieved in a study using a 2D electron gas in a compound semiconductor heterostructure (GaAs/AlGaAs) [18]. However, charge qubits typically have short coherence times (several ns), which is not enough to perform several thousand quantum gate operations before decoherence occurs.
Diamagnetic susceptibility of an artificial hydrogen molecule ion DD2 + confined to quantum dots: effects of anisotropy
Published in Philosophical Magazine, 2023
H. Sari, S. Sakiroglu, E. Kasapoglu, C. A. Duque
Technical feasibility of the adding of a single, magnetic or non-magnetic dopant in semiconductor nanostructures promotes the research on the electro-optical properties of QDs with singly-ionised double donor system (D) [38–40]. Peculiar features of this artificial molecular system, consisting of two positive charge centres with one ionised excess electron, and its implementation potential as a semiconductor charge qubit have drawn considerable interest in view of theoretical research [41, 42]. The dependence of the spontaneous emission rates, energy splittings and charge-density distributions in the lowest-lying sates of a double donor system in a spherical quantum dot is presented by Movilla et al. [43]. Results of the research show that confinement sources operating at different scales cause a variation in the tunnel coupling strength and radiative lifetimes. The evolution of the energies of some low-lying levels and their Aharonov–Bohm oscillations of a double-donor complex in vertically coupled quantum dots with magnetic field along the symmetry axis is reported by Manjarres-Garcia et al. [44]. Recently, in Ref. [45] researchers investigate the linear and non-linear optical absorption coefficients of a D complex in GaAs nano-scaled ring subjected to a uniform magnetic field. Obtained results indicate remarkable effect of the donors position, hydrostatic pressure, sample temperature and external magnetic field on the optical absorption of the system. In the theoretical study on the nonlinear optical rectification, the second- and third-harmonic generation of a singly ionised double donor in an asymmetric V-groove nanowire given in Ref. [46], molecular-like behaviour of energy levels and influence of the morphological parameters on the optical characteristics is discussed in detail.
Non-classicality of two superconducting-qubits interacting independently with a resonator cavity: trace-norm correlation and Bures-distance entanglement
Published in Journal of Modern Optics, 2021
A.-B. A. Mohamed, H. A. Hessian
The considered model consist of a pair of spatially isolated charge-qubits, which are individually coupled to a superconducting resonator [54–56]. The qubit-resonator interaction starts with a maximally entangled Bell-state. The charge-qubit is represented by a Cooper-pair box (CPB) contains two coupled junctions with the gate voltage source , the capacitance and the dimensionless gate charge . The tuning between the two junctions is occurred by applying a classical magnetic field with the capacitance and the energy . If the applied magnetic flux field is controlled, with respect to the flux quantum , to be and , the qubit-resonator system, in the rotating wave approximation, is described by the following Hamiltonian: [57–59], where , are frequencies of the i-qubit and i-resonator respectively. is the resonator operators. are the i-qubit operators which are spanned by the up and down states, and are the i-qubit operators. The frequency resonances (resonant/off-resonant) of i-qubit-resonator are represented by the qubit-resonator detuning: . It is also worth pointing out that the model in Equation (1) is very generic for many physical systems including cavity QED with neutral atoms, quantum dot systems and superconducting qubits.