Periodic Reporting for period 1 - pERFEcTO (EmpoweRing FundamEntal physics and Technology with quantum Optomechanics)
Reporting period: 2018-12-01 to 2020-11-30
pERFEcTO has explored the foundations of quantum theory at the interface with both gravity and thermodynamics with particular emphasis on the phenomenological possibilities offered by optomechanical platforms. We were able to connect theoretical results at the frontiers of quantum physics with ways to extract empirical evidence on them and feed them back into the development of future experimental efforts.
The questions investigated by pERFEcTO have a twofold impact. On the one hand, we have advanced the understanding of the interface between quantum theory and both gravity and thermodynamics, offering novel insights into theoretical problems. On the other hand, the search for phenomenological verifications of the theoretical results has led to the development of new methods to account for quantum effects in systems which will play a relevant role in future quantum technologies.
The overall objectives of pERFEcTO, entangling theoretical searches with the investigation of suitable technological platforms to probe them, were:
1) To unveil the fundamental structure of space-time using optomechanical quantum systems.
2) To discern between different interpretations of quantum mechanics with empirical observations.
3) To investigate thermodynamic irreversibility in macroscopic quantum systems undergoing non-equilibrium quantum processes.
The questions investigated by pERFEcTO have a twofold impact. On the one hand, we have advanced the understanding of the interface between quantum theory and both gravity and thermodynamics, offering novel insights into theoretical problems. On the other hand, the search for phenomenological verifications of the theoretical results has led to the development of new methods to account for quantum effects in systems which will play a relevant role in future quantum technologies.
The overall objectives of pERFEcTO, entangling theoretical searches with the investigation of suitable technological platforms to probe them, were:
1) To unveil the fundamental structure of space-time using optomechanical quantum systems.
2) To discern between different interpretations of quantum mechanics with empirical observations.
3) To investigate thermodynamic irreversibility in macroscopic quantum systems undergoing non-equilibrium quantum processes.
pERFEcTO’s work-programme has been structured and organised to address the objectives highlighted in the summary in a systematic way.
1. Interface between gravity/spacetime and quantum physics:
In a work appeared in Class. Quantum Gravity, we have put forward a Hamiltonian description of the non-local dynamics of a mechanical quantum oscillator stemming from a hypothetical small-scale structure of spacetime — characteristic of several quantum gravity models. This represents the first step towards a detailed description of optomechanical experiments aimed at unveiling these effects or ruling out the underlying theories. Further work is in progress, in collaboration with the group of Prof Marin in Florence.
In a work appeared in Nat. Commun., we have explored the interplay between quantum and time physics investigating how the concept of time localizability is affected in presence of quantum clocks.
Finally, in a work appeared in Phys. Rev. Lett., we have combined spacetime physics with indefinite causal order and shown that particle detectors can, if in a quantum-controlled superposition, harvest correlations from the vacuum of a field theory otherwise not possible to harvest.
2. Foundations of quantum physics and the quantum-to-classical transition:
The superposition principle is one of the basic tenants of quantum mechanics whose tests at mesoscopic scales are made extremely difficult by the fragility of quantum features. Experiments aiming at probing this principle, and with it also possible modifications of quantum mechanics, are under intense investigation. In a result selected as Editors’ Suggestion in Phys. Rev. A, we have extended the framework of near-field interferometry to account for large test particles. This result opened the way to performing accurate forecasts for near-field interferometry experiments both ground and space-based. We have employed these results in a recent pre-print where we showed the possibilities and limitations of ground-based matter-wave experiments with large nanoparticles.
In another recent pre-print, we have investigated the potential of Quantum Hypothesis Testing — a scheme that uses the notorious statistical inference techniques in combination with quantum resources — for studies of fundamental physics employing optomechanical set-ups. This study shows that quantum squeezed light offers an inference advantage with respect to comparable classical strategies.
3. Quantum physics and thermodynamics:
The interplay between quantum measurements and thermodynamics of quantum processes has been another pillar of pERFEcTO. In a work appeared in npj Quantum Inf., we have formulated a phase-space framework to account for the thermodynamic effect of continuously monitoring a quantum system. Successively, this framework has led to the first experimental assessment of irreversible entropy production in a mechanical mesoscopic quantum system, a result appeared as Editors’ Suggestion in Phys. Rev. Lett.
Quantum measurements are crucial ingredients also when it comes to characterising the statistic of relevant physical quantities, like work or entropy production. In a recent pre-print, we have proposed a change of paradigm with respect to the celebrated two-point measurement scheme -- used to verify the validity of the fluctuation theorem in quantum systems -- with a novel one-point measurement scheme. Our scheme does not lose information on the quantum coherence of the initial state of the process of interest, which is crucial for characterising the role of quantum correlations and coherence in the thermodynamics of quantum processes.
pERFEcTO has obtained several results at the frontiers of modern quantum physics. All these results have been disseminated via publications in top-tier peer-reviewed journals, social media (Twitter & Facebook dedicated accounts), a dedicated project website, and via seminars in academic institutions and participation at international conferences and workshops.
1. Interface between gravity/spacetime and quantum physics:
In a work appeared in Class. Quantum Gravity, we have put forward a Hamiltonian description of the non-local dynamics of a mechanical quantum oscillator stemming from a hypothetical small-scale structure of spacetime — characteristic of several quantum gravity models. This represents the first step towards a detailed description of optomechanical experiments aimed at unveiling these effects or ruling out the underlying theories. Further work is in progress, in collaboration with the group of Prof Marin in Florence.
In a work appeared in Nat. Commun., we have explored the interplay between quantum and time physics investigating how the concept of time localizability is affected in presence of quantum clocks.
Finally, in a work appeared in Phys. Rev. Lett., we have combined spacetime physics with indefinite causal order and shown that particle detectors can, if in a quantum-controlled superposition, harvest correlations from the vacuum of a field theory otherwise not possible to harvest.
2. Foundations of quantum physics and the quantum-to-classical transition:
The superposition principle is one of the basic tenants of quantum mechanics whose tests at mesoscopic scales are made extremely difficult by the fragility of quantum features. Experiments aiming at probing this principle, and with it also possible modifications of quantum mechanics, are under intense investigation. In a result selected as Editors’ Suggestion in Phys. Rev. A, we have extended the framework of near-field interferometry to account for large test particles. This result opened the way to performing accurate forecasts for near-field interferometry experiments both ground and space-based. We have employed these results in a recent pre-print where we showed the possibilities and limitations of ground-based matter-wave experiments with large nanoparticles.
In another recent pre-print, we have investigated the potential of Quantum Hypothesis Testing — a scheme that uses the notorious statistical inference techniques in combination with quantum resources — for studies of fundamental physics employing optomechanical set-ups. This study shows that quantum squeezed light offers an inference advantage with respect to comparable classical strategies.
3. Quantum physics and thermodynamics:
The interplay between quantum measurements and thermodynamics of quantum processes has been another pillar of pERFEcTO. In a work appeared in npj Quantum Inf., we have formulated a phase-space framework to account for the thermodynamic effect of continuously monitoring a quantum system. Successively, this framework has led to the first experimental assessment of irreversible entropy production in a mechanical mesoscopic quantum system, a result appeared as Editors’ Suggestion in Phys. Rev. Lett.
Quantum measurements are crucial ingredients also when it comes to characterising the statistic of relevant physical quantities, like work or entropy production. In a recent pre-print, we have proposed a change of paradigm with respect to the celebrated two-point measurement scheme -- used to verify the validity of the fluctuation theorem in quantum systems -- with a novel one-point measurement scheme. Our scheme does not lose information on the quantum coherence of the initial state of the process of interest, which is crucial for characterising the role of quantum correlations and coherence in the thermodynamics of quantum processes.
pERFEcTO has obtained several results at the frontiers of modern quantum physics. All these results have been disseminated via publications in top-tier peer-reviewed journals, social media (Twitter & Facebook dedicated accounts), a dedicated project website, and via seminars in academic institutions and participation at international conferences and workshops.
pERFEcTO results have furthered the state of the art in the fields of gravitational quantum physics and quantum thermodynamics by offering:
a) Theoretical evidence for furthering the investigation on the quantum nature of gravity and spacetime via quantum optomechanical set-ups
b) Extension to large quantum particles of the methods of near-field interferometry which has already found an application in pointing out the limitations and possibilities offered by ground-based experiments and will be the basis for future investigations aimed at testing quantum mechanics at larger and larger scales
c) Novel frameworks in quantum thermodynamics to account for the informational effect of continuous measurements on the thermodynamics of mesoscopic quantum systems with also experimental verifications
For the scientific community, these results offer novel tools for the exploration of the frontiers of quantum physics and, in particular, its interface with other fundamental theories. The major impact for society at large is the advancement in our understanding of fundamental physics problems and how quantum technologies can help us in this endeavour. These are fascinating topics which can help to raise the interest of the general public. In the long term, we envisage the relevance of our results, and their ramifications, in the development of quantum technologies employing the quantum features of mesoscopic systems in thermodynamic tasks.
a) Theoretical evidence for furthering the investigation on the quantum nature of gravity and spacetime via quantum optomechanical set-ups
b) Extension to large quantum particles of the methods of near-field interferometry which has already found an application in pointing out the limitations and possibilities offered by ground-based experiments and will be the basis for future investigations aimed at testing quantum mechanics at larger and larger scales
c) Novel frameworks in quantum thermodynamics to account for the informational effect of continuous measurements on the thermodynamics of mesoscopic quantum systems with also experimental verifications
For the scientific community, these results offer novel tools for the exploration of the frontiers of quantum physics and, in particular, its interface with other fundamental theories. The major impact for society at large is the advancement in our understanding of fundamental physics problems and how quantum technologies can help us in this endeavour. These are fascinating topics which can help to raise the interest of the general public. In the long term, we envisage the relevance of our results, and their ramifications, in the development of quantum technologies employing the quantum features of mesoscopic systems in thermodynamic tasks.