Operational Markov condition for quantum processes

Data underpinning publication in Pollock, F., Rodriguez-Rosario, C., Frauenheim, T., Paternostro, M., Modi, K., 2018, 'Operational Markov condition for quantum processes' Physical Review Letters, Volume 120, Issue 4

Out-of-equilibrium thermodynamics of quantum optomechanical systems

We address the out-of-equilibrium thermodynamics of an isolated quantum system consisting of a cavity optomechanical device. We explore the dynamical response of the system when driven out of equilibrium by a sudden quench of the coupling parameter and compute analytically the full distribution of the work generated by the process. We consider linear and quadratic optomechanical coupling, where the cavity field is parametrically coupled to either the position or the square of the position of a mechanical oscillator, respectively. In the former case we find that the average work generated by the quench is zero, whilst the latter leads to a non-zero average value. Through fluctuations theorems we access the most relevant thermodynamical figures of merit, such as the free energy difference and the amount of irreversible work generated. We thus provide a full characterization of the out-of-equilibrium thermodynamics in the quantum regime for nonlinearly coupled bosonic modes. Our study is the first due step towards the construction and full quantum analysis of an optomechanical machine working fully out of equilibrium

Positron cooling in CF4 and N2 gas: videos

Videos of the positron temperature and momentum distribution during cooling in CF4 and N2 gas from ~1500K

Reconciliation of quantum local master equations with thermodynamics

Datasets for all the figures included in the paper - 'Non-Gaussian distribution of collective operators in quantum spin chains', G. De Chiara et al. New J. Phys. 2018

Dataset for "A quantum fluctuation theorem for dissipative processes"

Dataset underpinning the research article: "A quantum fluctuation theorem for dissipative processes." We present a general quantum fluctuation theorem for the entropy production of an open quantum system coupled to multiple environments, not necessarily at equilibrium. Such general theorem, when restricted to the weak-coupling and Markovian regime, holds for both local and global master equations, corroborating the thermodynamic consistency of local quantum master equations. The theorem is genuinely quantum, as it can be expressed in terms of conservation of a Hermitian operator, describing the dynamics of the system state operator and of the entropy change in the baths. The integral fluctuation theorem follows from the properties of such an operator. Furthermore, it is also valid when the system is described by a time-dependent Hamiltonian. As such, the quantum Jarzynski equality is a particular case of the general result presented here. Moreover, our result can be extended to non-thermal baths, as long as microreversibility is preserved. We present some numerical examples to showcase the exact results previously obtained. We finally generalize the fluctuation theorem to the case where the interaction between the system and the bath is explicitly taken into account. We show that the fluctuation theorem amounts to a relation between time-reversed dynamics of the global density matrix and a two-time correlation function along the forward dynamics involving the baths’ entropy alone. Files accessible via Python

Many-body theory for positronium-atom interactions

Data underpinning publication in Green, D., Gribakin, G., Swann, A. 2018 'Many-body theory for positronium-atom interactions', Physical Review Letter

Spin and spatial dynamics in electron-impact scattering off S-wave He using R-matrix-with-time-dependence theory

Raw for electron-impact scattering from He generated using the RMT-DI code

Quantum machines powered by correlated baths

We consider thermal machines powered by locally equilibrium reservoirs that share classical or quantum correlations. The reservoirs are modelled by the so called collisional model or repeated interactions model. In our framework, two reservoir particles, initially prepared in a thermal state, are correlated through a unitary transformation and afterwards interact locally with the two quantum subsystems which form the working fluid. For a particular class of unitaries, we show how the transformation applied to the reservoir particles affect the amount of heat transferred and the work produced. We then compute the distribution of heat and work when the unitary is chosen randomly, proving that the total swap transformation is the optimal one. Finally, we analyse the performance of the machines in terms of classical and quantum correlations established among the microscopic constituents of the machine