arXiv subjects

Giovanni Spaventa

Publications and source records attributed to Giovanni Spaventa.

8 recordsLinked to original sources

arXiv2026

Approaching Resource-Theoretic Optimal Performance with Structured Environments

Resource-theoretic approaches to thermodynamics provide powerful, model-independent bounds on the efficiency of physical processes, because they do not rely on microscopic details of the environment. Whether such bounds can be approached by realistic dynamics generated by explicit system-environment interactions remains an open question. Photoisomerization, a fundamental molecular photoreaction, offers a concrete setting to examine this issue. We introduce a tunable microscopic model of a molecular photoswitch coupled to a structured vibrational environment, which interpolates continuously between Markovian and non-Markovian regimes. Resource-theoretic analysis predicts in particular that Markovian Thermal Operations achieve strictly lower yields than general Thermal Operations. We show that environmental memory lifts dynamical restrictions associated with Markovian thermal evolutions, thereby enlarging the set of transformations accessible to the microscopic dynamics. Approaching the thermal operation bound, however, depends on the microscopic coupling structure that generates this memory and directs the resulting dynamics towards the target transformation.

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arXiv2026

Gaussian time-translation covariant operations: structure, implementation, and thermodynamics

Time-translation symmetry strongly constrains physical dynamics, yet systematic characterization for continuous-variable systems lags behind its discrete-variable counterpart. We close this gap by providing a rigorous classification of Gaussian quantum operations that are covariant under time translations, termed Gaussian covariant operations. We show that several key results known for discrete-variable covariant operations break down in the Gaussian optical setting: discrepancies arise in physical and thermodynamic implementation, in the extensivity of asymmetry, and in catalytic advantages. Our results provide comprehensive mathematical and operational toolkits for Gaussian covariant operations, including a peculiar pair of asymmetry measures that are completely non-extensive. Our findings also reveal surprising consequences of the interplay among symmetry, Gaussianity, and thermodynamic constraints, suggesting that real-world scenarios with multiple constraints have a rich structure not accessible from examining individual constraints separately.

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arXiv2025

Correlated dynamics as a resource in molecular switches

Photoisomerization, a photochemical process underlying many biological mechanisms, has been modeled recently within the quantum resource theory of thermodynamics. This approach has emerged as a promising tool for studying fundamental limitations to nanoscale processes independently of the microscopic details governing their dynamics. On the other hand, correlations between physical systems have been shown to play a crucial role in quantum thermodynamics by lowering the work cost of certain operations. Here, we explore quantitatively how correlations between multiple photoswitches can enhance the efficiency of photoisomerization beyond that attainable for single molecules. Furthermore, our analysis provides insights into the interplay between quantum and classical correlations in these transformations.

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arXiv2024

Quantum resource-theoretical analysis of the role of vibrational structure in photoisomerization

Thermodynamical systems at the nanoscale, such as single molecules interacting with highly structured vibrational environments, typically undergo non-equilibrium physical processes that lack precise microscopic descriptions. Photoisomerization is such an example which has emerged as a platform on which to study single-molecule ultrafast photochemical processes from a quantum resource theoretic perspective. However, upper bounds on its efficiency have only been obtained under significant simplifications that make the mathematics of the resource-theoretical treatment manageable. Here we generalize previous models for the photoisomers, while retaining the full vibrational structure, and still get analytical bounds on the efficiency of hotoisomerization. We quantify the impact of such vibrational structure on the optimal photoisomerization quantum yield both when the vibrational coordinate has no dynamics of its own and when we take into account the vibrational dynamics. This work serves as an example of how to bridge the gap between the abstract language of quantum resource theories and the open system formulation of nanoscale processes.

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arXiv2024

Physically constrained quantum clock-driven dynamics

Thermal machines are physical systems designed to convert thermal energy into practical work through cyclic state transformations. A key component in such a machine is a clock-equipped control element that dictates which interaction Hamiltonian governs the system-reservoir interactions at specific times, while itself remaining unaffected. However, in the context of quantum dynamics, it is well known that maintaining perfect isolation is practically impossible, except under highly idealized conditions. In this study, we begin with such an idealized model for a clock and systematically relax its main assumptions to develop a more realistic framework. Our approach yields a simplified yet physically consistent description of clock dynamics, enabling the analysis of deviations from ideal time-keeping, which we interpret as clock degradation. We introduce a continuous time operator to derive a lower bound on this degradation, grounded in a generalized time-energy uncertainty relation. These results highlight trade-offs between clock performance and energy uncertainty in physically realizable control schemes.

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arXiv2023

On tests of the quantum nature of gravitational interactions in presence of non-linear corrections to quantum mechanics

When two particles interact primarily through gravity and follow the laws of quantum mechanics, the generation of entanglement is considered a hallmark of the quantum nature of the gravitational interaction. However, we demonstrate that entanglement dynamics can also occur in the presence of a weak quantum interaction and non-linear corrections to local quantum mechanics, even if the gravitational interaction is classical or absent at short distances. This highlights the importance of going beyond entanglement detection to conclusively test the quantum character of gravity, and it requires a thorough examination of the strength of other quantum forces and potential non-linear corrections to quantum mechanics in the realm of large masses.

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arXiv2022

Nature and origin of the operators entering the master equation of an open quantum system

By exploiting the peculiarities of a recently introduced formalism for describing open quantum systems (the Parametric Representation with Environmental Coherent States) we derive an equation of motion for the reduced density operator of an open quantum system that has the same structure of the celebrated Gorini-Kossakowski-Sudarshan-Lindblad equation, but holds regardless of markovianity being assumed. The operators in our result have explicit expressions in terms of the Hamiltonian describing the interactions with the environment, and can be computed once a specific model is considered. We find that, instead of a single set of Lindblad operators, in the general (non-markovian) case there one set of Lindblad-like operators for each and every point of a symplectic manifold associated to the environment. This intricacy disappears under some assumptions (which are related to markovianity and the classical limit of the environment), under which it is possible to recover the usual master equation formalism. Finally, we find such Lindblad-like operators for two different models of a qubit in a bosonic environment, and show that in the classical limit of the environment their renown master equations are recovered.

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arXiv2022

Capacity of non-Markovianity to boost the efficiency of molecular switches

Quantum resource theory formulations of thermodynamics offer a versatile tool for the study of fundamental limitations to the efficiency of physical processes, independently of the microscopic details governing their dynamics. Despite the ubiquitous presence of non-Markovian dynamics in open quantum systems at the nanoscale, rigorous proofs of their beneficial effects on the efficiency of quantum dynamical processes at the bio-molecular level have not been reported yet. Here we combine the resource theory of athermality with concepts from the theory of divisibility classes for quantum channels, to prove that memory effects can increase the efficiency of photoisomerization to levels that are not achievable under a purely thermal Markovian (i.e. memoryless) evolution. This provides rigorous evidence that memory effects can provide a resource in biological quantum dynamics, and, more generally, quantum thermodynamics at the nanoscale.

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