Search results for "dephasing"
showing 10 items of 73 documents
Instantaneous diffusion effect on spin-echo decay: Experimental investigation by spectral selective excitation
2001
The influence of the instantaneous diffusion process on spin-echo decay of ${E}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ centers in gamma irradiated silica is experimentally probed by spectral selective excitation within their inhomogeneous resonance line. Our results evidence the different effectiveness of this dephasing mechanism on varying the resonance field, manifesting itself by a faster decay of the echo signal when generated by spin packets located in the central part of the spectrum. It is shown that the dependence of the instantaneous diffusion rate on the spectral position of echo-active spins reproduces the shape of the ${E}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ centers resonan…
Geometric phase in open systems.
2003
We calculate the geometric phase associated to the evolution of a system subjected to decoherence through a quantum-jump approach. The method is general and can be applied to many different physical systems. As examples, two main source of decoherence are considered: dephasing and spontaneous decay. We show that the geometric phase is completely insensitive to the former, i.e. it is independent of the number of jumps determined by the dephasing operator.
Analysis of femtosecond Raman-induced polarization spectroscopy (RIPS) in N2 and CO2 by fitting and scaling laws
2000
Raman-induced polarization spectroscopy (RIPS) experiments were conducted at room temperature and pressures below 2 atm in pure N2 and CO2. Both homodyne and optically heterodyne detection were used. Calculations of the signal as a function of the pump–probe delay were performed taking into account the pulse duration of the laser, the rotational dependence of the dephasing rates and the small instantaneous electronic Kerr effect. The observed decay and shape of the rotational quantum beats are in good agreement with the calculations. Several sets of linewidth coefficients corresponding to the diagonal part of the collisional–rotational relaxation matrix were used. This matrix was choosen am…
Absence of mutual polariton scattering for strongly coupled surface plasmon polaritons and dye molecules with a large Stokes shift
2013
The understanding and control of the dynamics of hybrid modes consisting of strongly coupled surface plasmon polaritons and molecular excitations of dye molecules is of great timely interest, as it allows one to tailor interactions between optical signals as needed for active all-optical devices. Here we utilize dye molecules with an especially large Stokes shift to demonstrate the absence of mutual scatterings among the strongly coupled hybrid modes. We employ a quantum mechanical three-level model and show that the hybrid modes decay via dephasing and internal relaxation of the molecules to a fluorescing state of the dye, which can be used as a measure for the decay. Our results provide e…
Vibrational dephasing of νs(OH) in 2,6-dichloro-4-nitrophenol
1988
Abstract A detailed analysis of the infrared bandshape of ν s (OH) in intramolecularly hydrogen-bonded 2,6-dichloro-4-nitrophenol in a series of solvents is presented. A distinct dependence of the bandshape and relaxation parameters on the polarity of solvent molecules has been found. The band shifts to lower wavenumbers, broadens and becomes more Gaussian with increasing solvent polarity; correspondingly, the correlation function decays faster and the correlation time decreases. The results are compared with those of previously studied systems. Factors determing the bandshape are discussed.
Infrared bandshapes of intramolecularly H-bonded systems—III. Vibrational dephasing of vs (OH) in 2,6-dichlorophenol
1987
Abstract The shape of the v s (OH) absorption band of intramolecularly H-bonded 2,6-dichlorophenol was measured in a series of solvents of increasing polarity and quantitatively analyzed. A distinct dependence of band positions, shape parameters, band moments, integrated intensities, correlation functions and correlation times on the polarity of solvent has been found. Vibrational dephasing due to dipole—dipole interactions seems to be an important relaxation pathway determining the bandshape in the studied systems.
Unveiling the Effect of Magnetic Noise in the Coherence of Single-Molecule Quantum Processors.
2019
Quantum bits (qubits) constitute the most elementary building-blocks of any quantum technology, where information is stored and processed in the form of quantum superpositions between discrete energy levels. In particular, the fabrication of quantum processors is a key long-term goal that will allow us conducting specific tasks much more efficiently than the most powerful classical computers can do. Motivated by recent experiments in which three addressable spin qubits are defined on a potential single-molecule quantum processor, namely the [Gd(H2O)P5W30O110]12− polyoxometalate, we investigate the decohering effect of magnetic noise on the encoded quantum information. Our state-of-the-art m…
The quantum trajectory approach to geometric phase for open systems
2005
The quantum jump method for the calculation of geometric phase is reviewed. This is an operational method to associate a geometric phase to the evolution of a quantum system subjected to decoherence in an open system. The method is general and can be applied to many different physical systems, within the Markovian approximation. As examples, two main source of decoherence are considered: dephasing and spontaneous decay. It is shown that the geometric phase is to very large extent insensitive to the former, i.e. it is independent of the number of jumps determined by the dephasing operator.
Nuclear Magnetic Resonance for Cultural Heritage
2007
Abstract Nuclear magnetic resonance (NMR) portable devices are now being used for nondestructive in situ analysis of water content, pore space structure and protective treatment performance in porous media in the field of cultural heritage. It is a standard procedure to invert T 1 and T 2 relaxation data of fully water-saturated samples to get “pore size” distributions, but the use of T 2 requires great caution. It is well known that dephasing effects due to water molecule diffusion in a magnetic field gradient can affect transverse relaxation data, even if the smallest experimentally available half echo time τ is used in Carr–Purcell–Meiboom–Gill experiments. When a portable single-sided N…
Measurement and dephasing of a flux qubit due to heat currents
2013
We study a flux qubit, made of a superconducting loop interrupted by three Josephson junctions, which is subject to a temperature gradient. We show that the heat current induced by the temperature gradient, being sensitive to the superconducting phase differences at the junctions, depends significantly on the state of the qubit. We furthermore investigate the impact of the heat current on the coherence properties of the qubit state. We have found that even small temperature gradients can lead to dephasing times of the order of microseconds for the Delft-qubit design.