Simulating and Optimising Quantum Thermometry Using Single Photons.

A classical thermometer typically works by exchanging energy with the system being measured until it comes to equilibrium, at which point the readout is related to the final energy state of the thermometer. A recent paper noted that with a quantum thermometer consisting of a single spin/qubit, temperature discrimination is better achieved at finite times rather than once equilibration is essentially complete. Furthermore, preparing a qubit thermometer in a state with quantum coherence instead of an incoherent one improves its sensitivity to temperature differences. Implementing a recent proposal for efficiently emulating an arbitrary quantum channel, we use the quantum polarisation state of individual photons as models of "single-qubit thermometers" which evolve for a certain time in contact with a thermal bath. We investigate the optimal thermometer states for temperature discrimination, and the optimal interaction times, confirming that there is a broad regime where quantum coherence provides a significant improvement. We also discuss the more practical question of thermometers composed of a finite number of spins/qubits (greater than one), and characterize the performance of an adaptive protocol for making optimal use of all the qubits.

Molecular topology and quantum chemical descriptors in the study of reversed-phase liquid chromatography. Hydrogen-bonding behavior of chalcones and flavanones.

The reversed-phase liquid chromatographic hydrophobicity parameters (log K'w and S) of several chalcones and flavanones were determined with methanol:water mobile phases of different compositions and with trace quantities of n-decylamine and 1-octanol added to the eluent to minimize the silanophilic interactions present in alkylsilane-bonded phases. It has been reported that qualitative hydrogen bonding information can be obtained from the relationship between S and log K'w determined with these chromatographic conditions. To quantitatively describe the hydrogen-bonding discrimination effects observed for the compounds under study, the parameter delta was defined as follows: delta(s-log kw) = S-log K'w. With topological and molecular orbital calculations, several molecular descriptors were computed for test compounds, and multivariate statistical techniques were used to examine the informative value of the parameter proposed. The results obtained indicate that delta(s-log Kw) encodes structural information mainly related to the molecular polarity and the ability of compounds to participate in hydrogen-bonding interactions. Similar structural information was also obtained for delta(s-log Kw) values of 31 structurally dissimilar compounds.