arXiv subjects

A. D'Arrigo

Publications and source records attributed to A. D'Arrigo.

25 records · Page 2Linked to original sources

arXiv2008

Effects of low-frequency noise cross-correlations in coupled superconducting qubits

We study the effects of correlated low frequency noise sources acting on a two qubit gate in a fixed coupling scheme. A phenomenological model for the spatial and cross-talk correlations is introduced. The decoherence inside the SWAP subspace is analysed by combining analytic results based on the adiabatic approximation and numerical simulations. Results critically depend on amplitude of the low frequency noise with respect to the qubits coupling strength. Correlations between noise sources induce qualitative different behaviors depending on the values of the above parameters. The possibility to reduce dephasing due to correlated low frequency noise by a recalibration protocol is discussed.

cond-mat.supr-con↗

arXiv2008

Semiclassical model for a memory dephasing channel

We study a dephasing channel with memory, described by a Hamiltonian model in which the system-environment interaction is described by a stochastic process. We propose a useful way to describe the channel uses correlations. Moreover, we give a general expression for the coherences decay factors as a function of the number of channel uses and of the stochastic process power spectrum. We also study the impact of memory on the three qubit code, showing that correlations among channel uses affect very little the code performance.

quant-ph↗

arXiv2007

Memory effects in quantum information transmission across a Hamiltonian dephasing channel

We study a dephasing channel with memory, modelled by a multimode environment of oscillators. Focusing on the case of two channel uses, we show that memory effects can enhance the amount of coherent quantum information transmitted down the channel. We also show the Kraus representation for two channel uses. Finally, we propose a coding-decoding scheme that takes advantage of memory to improve the fidelity of transmission.

quant-ph↗

arXiv2005

Initial decoherence in solid state qubits

We study decoherence due to low frequency noise in Josephson qubits. Non-Markovian classical noise due to switching impurities determines inhomogeneous broadening of the signal. The theory is extended to include effects of high-frequency quantum noise, due to impurities or to the electromagnetic environment. The interplay of slow noise with intrinsically non-gaussian noise sources may explain the rich physics observed in the spectroscopy and in the dynamics of charge based devices.

cond-mat.mes-hall↗

arXiv2004

Dynamical suppression of telegraph and 1/f noise due to quantum bistable fluctuator

We study dynamical decoupling of a qubit from non gaussian quantum noise due to discrete sources, as bistable fluctuators and 1/f noise. We obtain analytic and numerical results for generic operating point. For very large pulse frequency, where dynamic decoupling compensates decoherence, we found universal behavior. At intermediate frequencies noise can be compensated or enhanced, depending on the nature of the fluctuators and on the operating point. Our technique can be applied to a larger class of non-gaussian environments.

cond-mat.mes-hall↗

arXiv2004

Decoherence due to telegraph and 1/f noise in Josephson qubits

We study decoherence due to random telegraph and 1/f noise in Josephson qubits. We illustrate differences between gaussian and non gaussian effects at different working points and for different protocols. Features of the intrinsically non-gaussian and non-Markovian low-frequency noise may explain the rich physics observed in the spectroscopy and the dynamics of charge based devices.

cond-mat.mes-hall↗

arXiv2000

The Halo of 14Be

The two-neutron halo nucleus 14Be has been investigated in a kinematically complete measurement of the fragments (12Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross-sections, neutron angular distributions and invariant mass spectra characteristic of a halo were observed and the electromagnetic (EMD) contributions deduced. Comparison with three-body model predictions indicate that the halo wavefunction contains a large 2s1/2^2 admixture. The EMD invariant mass spectrum exhibited a relatively narrow structure near threshold (Edecay=1.8+/-0.1 MeV, Gamma = 0.8+/-0.4 MeV) consistent with a soft-dipole excitation.

nucl-ex↗