24 research outputs found
Water activity and freezing points in aqueous solutions of manganese nitrate: experimental and modeling
The water activities of manganese nitrate solutions were measured using a
humidity sensor instrument up to almost the saturation molality at 298.15 K; the thermodynamic
properties of the system were described by the Pitzer model and specific
interaction theory (SIT). The evaluation of the ion interaction parameters for the Pitzer
model and SIT were carried out using experimental freezing points and osmotic coefficients
of manganese nitrate aqueous solutions, collected from the open literature, and the
water activity data measured in this work. A set of Pitzer and SIT parameters were
estimated using a temperature dependency, that enables us to cover wider temperature
ranges, and consequently calculate system properties to higher molalities. Both approaches
represent very satisfactorily, and with similar accuracy, the experimental data and the
calculated manganese nitrate molal activity coefficients are comparable to those already
published for analogous systems. Additionally, the Pitzer model was also able to calculate
the ice curve and the solubility branch of manganese nitrate hexahydrate up to a salt
solution 6.5 mol-kg-1.This work was developed in the scope of the projects POCI-01-0145-FEDER-
006984—Associate Laboratory LSRE-LCM both funded by European Regional Development Fund (ERDF)
through COMPETE2020—Programa Operacional Competitividade e Internacionalização (POCI)—and by
national funds through FCT—Fundação para a Ciência e a Tecnologia. This work is also a result of project
‘‘AIProcMat@N2020—Advanced Industrial Processes and Materials for a Sustainable Northern Region of
Portugal 2020’’, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal
Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through
ERDF.info:eu-repo/semantics/publishedVersio
Coherent feedback control of a single qubit in diamond
Engineering desired operations on qubits subjected to the deleterious effects of their environment is a critical task in quantum information processing, quantum simulation and sensing. The most common approach is to rely on open-loop quantum control techniques, including optimal control algorithms, based on analytical or numerical solutions, Lyapunov design and Hamiltonian engineering. An alternative strategy, inspired by the success of classical control, is feedback control. Because of the complications introduced by quantum measurement, closed-loop control is less pervasive in the quantum settings and, with exceptions, its experimental implementations have been mainly limited to quantum optics experiments. Here we implement a feedback control algorithm with a solid-state spin qubit system associated with the Nitrogen Vacancy (NV) centre in diamond, using coherent feedback [9] to overcome limitations of measurement-based feedback, and show that it can protect the qubit against intrinsic dephasing noise for milliseconds.United States. Air Force Office of Scientific Research (Grant FA9550-12-1-0292)United States. Office of Naval Research (Grant N00014-14-1-0804