QTeQ’s recent research work has been published in the pages of the prestigious Nature Quantum Information (https://doi.org/10.1038/s41534-020-00334-6). In this work, the team composed by QTeQ members (Alessio Belenchia, Luca Mancino and Mauro Paternostro) and Gabriel Landi from the University of São Paolo explored the thermodynamics of quantum systems under continuous monitoring.

The work uses a phase-space description of the dynamics of open quantum system continuously monitored by quantum-limited detectors to infer the effect of the acquired information on the thermodynamics of the process. The final result is a refined second-law of thermodynamics expressed via the irreversible entropy production rate and directly connected to the information acquired via continuous monitoring. This theoretical framework has been used recently in an experimental investigation leading to the first experimental assessment of the irreversible entropy production for a quantum mesoscopic system (see the previous post).

rpuebla
December 10, 2020

In the beginning of 2020, QTeQ’s was published in Nature Photonics (*https://www.nature.com/articles/s41566-019-0553-9*)! This work, result of the fruitful collaboration with Sylvain Gigan’s group at the Laboratoire Kastler Brossel (ENS-PSL) in Paris, explored the potential of complex media, embodied here as multimode optical fibres, for quantum information processing and computation.

)! This work, result of the fruitful collaboration with Sylvain Gigan’s group at the Laboratoire Kastler Brossel (ENS-PSL) in Paris, explored the potential of complex media, embodied here as multimode optical fibres, for quantum information processing and computation.

The team in Paris demonstrated excellent control over the the two-photon dynamics throughout a multimode fibre, as well as the capability to control independently spatial and polarisation degrees of freedom of single photons. Scaling up such technology could allow for easier control of complex dynamics without needing to fine-tune the devices implementing the quantum evolution.

Well done and congrats on the article!!

QTeQ’s recent research work has been selected as Editor’s Suggestion in the prestigious Phys. Rev. Lett (*https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.080601*). In this recent work, with leading author Dr Massimiliano Rossi, from the Niels Bohr Institute in Copenaghen, a team of physicists led by our Dr Alessio Belenchia explored the thermodynamics of a mesoscopic quantum system under continuous monitoring.

The experimental component of the work, carried out by the group of Prof Schliesser in Copenhagen, in combination with the theoretical developments achieved by the QTeQ in collaboration with Prof Landi from São Paolo, was able to directly observe for the first time the stochastic entropy production and the effect of continuous measurement on a mesoscopic quantum mechanical oscillator. These results, while important from the conceptual point of view, open also the way to thermodynamically optimal protocols with mesoscopic quantum systems.

Very well done and congratulations on the great article!!

Despite the unusual circumstances, QTeQ has published several works in Physical Review in the first half of 2020, highlighting QTeQ’s top-quality research and fruitful collaborative environment: 3 Phys. Rev. Lett. (summarized below), 2 Phys. Rev. Research, 1 Phys. Rev. B and 2 Phys. Rev. E. Well done!!

In the first of the 2020’s QTeQ’s PRLs, “Machine learning-based classification of vector vortex beams” Phys. Rev. Lett. 124, 160401 (2020), done in collaboration with Fabio Sciarrino’s group at Sapienza Università di Roma, QTeQ’s endeavors have focused on the machine learning side, in particular, in the use of convolutional neural networks and principal component analysis for the classification of specific and complex polarization patterns. This work demonstrates the significant advantages resulting from the use of machine learning-based protocols for the construction and characterization of high-dimensional resources for quantum protocols.

The second PRL in the list goes to “Quantum State Engineering by Shortcuts to Adiabaticity in Interacting Spin-Boson Systems” Phys. Rev. Lett. 124, 180401 (2020), a QTeQ-made work where shortcuts-to-adiabaticity protocols have been demonstrated to be very well suited to generate a breadth of quantum states with very high fidelities, while allowing for a reduced evolution time for their preparation and thus naturally robust against potential decoherence processes. Thanks to the ubiquity of the considered Jaynes-Cummings interaction, such protocols can be relevant in several experimental platforms, where interesting quantum states could be realize, such as Fock states, cat-like superposition thereof, and states akin to photon-added and subtracted.

The third PRL goes to a novel phenomenon blending nonequilibrium dynamics and open quantum systems, “Universal anti-Kibble-Zurek scaling in fully-connected systems” Phys. Rev. Lett. 124, 230602 (2020), done in collaboration with Andrea Smirne (Milan) and Susana F. Huelga and Martin B. Plenio (Ulm). Although a driven critical system features Kibble-Zurek scaling laws, those are typically sensitive to the unavoidable system-environment interaction leading to an anti-Kibble-Zurek effect, namely, the slower the quench, the more nonequilibrium excitations are created. In this work we have shown that, even when the standard (isolated) scaling laws break down due to the open nature of the dynamics, there is an anti-Kibble-Zurek scaling which depends solely on the equilibrium critical exponents of the phase transition.

Keep up the momentum!!

QTeQ is proud of their own Luca Innocenti, who successfully defended his PhD thesis today 12th of June 2020. Luca’s work, which blended theory and experiments addressing the use of machine learning in quantum physics, was assessed by Gabriele (internal examiner) and Prof. Marco Barbieri from University Roma Tre (Italy).

Well done Luca!!

Congratulations to Alessio and co-workers on their recently accepted paper in the prestigious Nature Communications (*https://www.nature.com/articles/s41467-020-16013-1*) on quantum clocks and the temporal localisability of events in the presence of gravitating quantum systems!!

In this recent work, with lead author Dr Esteban Castro-Ruiz, a team of physicists led by Professor Caslav Brukner from the University of Vienna and the Institute for Quantum Optics and Quantum Information (IQOQI) Vienna explored the temporal localisability of events when quantum systems influence space-time according to Einstein’s general relativity. Dr Alessio Belenchia, from Queen’s University Belfast, is among the authors of this new work.

The study develops a framework to operationally define events and their localisation with respect to a quantum clock reference frame, also in the presence of gravitating quantum systems. The major results are that the time localisability of events becomes relative, depending on the reference frame, and that for each event there exists always a (quantum) clock according to which that event occurs at a sharp, precise time. This is useful because, using this clock as a reference, the time evolution of quantum systems still can be described similarly as in the ordinary situations where all events are localised in time.

QTeQ is delighted to announce that Dr. Alberto Imparato will be joining us from January to July 2020 in Belfast! Alberto Imparato is an expert on statistical physics, and in particular on out-of-equilibrium systems and autonomous motors. He is currently an Associate Professor at Aarhus University (Denmark) in the Department of Physics and Astronomy (see *https://pure.au.dk/portal/en/persons/alberto-imparato(276d5469-b076-44a1-9e0e-beca7be34621).html*). Alberto has taken a sabbatical to join us in Belfast; it will be a pleasure to combine efforts and expertise to develop new ideas and exciting projects!

Welcome Alberto!!

rpuebla
February 12, 2020

A new QTeQ paper on macrorealism has just been accepted by Journal of Physics B (available here: *https://iopscience.iop.org/article/10.1088/1361-6455/ab6d18/meta*). The paper, written by Marta Marchese and Hannah McAleese, proposes a test of macrorealism on a hybrid optomechanical system in which the mechanical oscillator occupies states which are macroscopically distinguishable. The violation of Leggett-Garg inequalities in this scheme confirms that the assumptions of both macroscopic realism and non-invasive measurability are invalid.

Well done! 🙂

A PhD position is available immediately to work at the Quantum Technology Group at Queen’s with Prof. Mauro Paternostro on non-equilibrium quantum thermodynamics enhanced by machine learning. The position will be funded by the Royal Society Wolfson Research Fellowship recently awarded to Prof. Mauro Paternostro. Applications through the CTAMOP portal (*https://web.am.qub.ac.uk/wp/ctamop/postgrad/*) will be accepted until 13 December 2019. All applicants will be interviewed and the successful candidate is expected to start in early 2020.

rpuebla
November 21, 2019

A postdoctoral research position to undertake theoretical research on “Quantum Thermodynamics” for 30 months from 01/05/2020 to 31/10/2022 is open for applications (*https://hrwebapp.qub.ac.uk/tlive_webrecruitment/wrd/run/ETREC107GF.open?VACANCY_ID=654832CDsK&WVID=6273090Lgx&LANG=USA*) until 03/01/2020. This post will be funded by an EPSRC grant entitled “Quantum Many-Body Engines” awarded to Dr. Gabriele De Chiara. The project will be conducted in collaboration with experimental groups working on ultracold atomic setups with the aim of designing and realising experimentally quantum thermodynamic machines. More details are available here (*https://gow.epsrc.ukri.org/NGBOViewGrant.aspx?GrantRef=EP/S02994X/1*)

Thanks to the tremendous advance in the experimental realisations of quantum technologies applications of thermodynamics with quantum devices are foreseeable in the near future. In the new emerging field of quantum thermodynamics a considerable effort is being devoted to the design and analysis of thermal machines and refrigerators operating at the quantum level and the theoretical foundation of thermodynamics from quantum principles, including the definition of thermodynamic quantities like heat and work, with inputs from quantum information theory.

There are currently several attempts at realising quantum machines, capable of producing work, with a few degrees of freedom, e.g. a single particle. Although quantum thermodynamics is developing very fast, it is not yet clear how to scale up such machines to systems composed of many quantum particles. This achievement would enable practical applications of quantum machines as autonomous devices capable of correcting errors and imperfections in quantum simulators and quantum computers as well as serving as assemblers of quantum materials at the nanoscale.

The overarching challenge of this project is to theoretically design thermal machines, that use as working substance an ensemble of many interacting quantum particles. More specifically, we will consider a network of interacting quantum particles, quantum harmonic oscillators and localised spins, externally driven and coupled to thermal and non-equilibrium reservoirs. The network will be arranged in order to transform heat into mechanical work, thus operating as a thermal engine, or to employ external work to extract heat from a cold reservoir for the realisation of a refrigerator. As a further step, we will optimise the geometry and architecture of the network itself to deliver work and refrigeration with the largest power and efficiency. Since it would be a formidable task to optimise all the tens of parameters of the Hamiltonian, we will employ machine learning techniques to this end. Finally, an important fraction of the project will be done in collaboration with two experimental groups working on ultracold atoms with the aim of designing thermal machines that can be realised with their current experimental setups. In collaboration with J. Sherson (Aarhus) we will design an engine whose working substance and reservoirs are realised with ultracold atoms in optical lattice potentials. In collaboration with T. Donner (Zürich) we will design a refrigerator made of two atomic Bose-Einstein condensates that interact with the common mode of an optical cavity.