We investigate the influence of the seed of measurement on the performance of a Szilard engine based on a two-mode Gaussian state evolving in a noisy channel. Quantum work is extracted by performing a positive operator-valued measurement (POVM) on one of the two modes, after which this mode reaches equilibrium with the environment. As the seed of measurement, we use a single-mode squeezed thermal state. We employ the Markovian Kossakowski-Lindblad master equation to determine the evolution in time of the considered open system and the quantum work is defined based on the Rényi entropy of order 2. We show that the extracted quantum work and information-work efficiency strongly depend on the characteristic parameters of the system (frequency, average thermal photons number, and squeezing), the noisy channel (temperature and squeezing of the bath), and the seed of measurement (average thermal photons number and strength of the measurement).
We investigate the influence of the seed of measurement on the performance of a Szilard engine based on a two-mode Gaussian state evolving in a noisy channel. Quantum work is extracted by performing a positive operator-valued measurement (POVM) on one of the two modes, after which this mode reaches equilibrium with the environment. As the seed of measurement, we use a single-mode squeezed thermal state. We employ the Markovian Kossakowski-Lindblad master equation to determine the evolution in time of the considered open system and the quantum work is defined based on the Rényi entropy of order 2. We show that the extracted quantum work and information-work efficiency strongly depend on the characteristic parameters of the system (frequency, average thermal photons number, and squeezing), the noisy channel (temperature and squeezing of the bath), and the seed of measurement (average thermal photons number and strength of the measurement).
We study a Szilard engine based on a Gaussian state of a system consisting of two bosonic modes placed in a noisy channel. As the initial state of the system is taken an entangled squeezed thermal state, and the quantum work is extracted by performing a measurement on one of the two modes. We use the Markovian Kossakowski-Lindblad master equation for describing the time evolution of the open system and the quantum work definition based on the second order Rényi entropy to simulate the engine. We also study the information-work efficiency of the Szilard engine as a function of the system parameters. The efficiency is defined as the ratio of the extractable work averaged over the measurement angle and the erasure work, which is proportional to the information stored in the system. We show that the extractable quantum work increases with the temperature of the reservoir and the squeezing between the modes, average numbers of thermal photons and frequencies of the modes. The work increases also with the strength of the measurement, attaining the maximal values in the case of a heterodyne detection. The extractable work is decreasing by increasing the squeezing parameter of the noisy channel and it oscillates with the phase of the squeezed thermal reservoir. The efficiency mostly has a similar behavior with the extractable quantum work evolution. However information-work efficiency decreases with temperature, while the quantity of the extractable work increases.
Nowadays, it is widely acknowledged that information can serve as a thermodynamic fuel capable of powering the extraction of useful work through measurements and feedback control. Moreover, it has been demonstrated that the work extractable from a correlated bipartite state can effectively distinguish entangled states from separable ones. In this context, we introduce an operational criterion denoted as [Formula: see text] to witness the presence of entanglement in a two-mode Gaussian state [Formula: see text], based on the amount of work that can be extracted from a thermal bath using a Szilard-like engine. In this setup, the state [Formula: see text] acts as the working medium of the engine, where modes [Formula: see text] and [Formula: see text] are generated during the first and second transitions of a nondegenerate three-level laser, and are coupled to a shared two-mode thermal bath. Our results reveal that the proposed criterion [Formula: see text] vanishes when [Formula: see text] is a product state. Furthermore, [Formula: see text] reaches its maximum value when [Formula: see text] is coupled to a vacuum bath, but it diminishes under the influence of thermal noise. Notably, the degree of entanglement detected by [Formula: see text] can be tuned via the atomic coherence of the laser. Finally, a comparison of [Formula: see text] with a reliable measure of entanglement such as logarithmic negativity, demonstrates perfect agreement in identifying the presence of entanglement in [Formula: see text].
The Szilard engine is a foundational thought experiment that rigorously links thermodynamicsand information theory. With the miniaturization of devices and ongoingprogress in quantum information science, it is crucial to examine how quantumeffects influence the operation of such engines. This thesis investigates the finitetimedynamics of a quantum Szilard engine subjected to size-invariant shape transformations,in which the geometry of the confinement potential is deformed withoutaltering its overall size. The system’s evolution is modeled using a time-dependent,Markovian LGKS (Lindblad-Gorini-Kossakowski-Sudarshan) master equation. Wenumerically solve this equation to analyze the thermodynamic behavior of the engine,focusing on the roles of quantum coherence and its interplay with heat, work,and entropy throughout the cycle. Special attention is given to how coherenceevolves under varying barrier insertion rates and thermalization temperatures. Wedemonstrate that coherence generation is strongly influenced by both the protocolspeed and the bath temperature. Furthermore, we show a connection between coherenceaccumulation and the energetic and informational cost of the cycle. Thesefindings enhance our understanding of coherence in finite-time, measurement-basedquantum devices and suggest that geometric deformations can serve as a powerfultool for thermodynamic control in quantum technologies.
Measurement-based quantum heat engines have attracted significant interest as alternatives to conventional thermal engines, as they replace the hot thermal reservoir with quantum measurements, thereby offering greater controllability and simpler implementation. Motivated by these advantages, we investigate a measurement-driven quantum Otto engine with a qubit working substance and study the optimal work extractable from such engines, including whether their performance can surpass that of conventional quantum Otto cycles. We analyze the engine in both the infinite-time (adiabatic) and finite-time (non-adiabatic) regimes, considering two distinct implementations obtained through optimization over all projection-valued measurements (PVMs) and over all two-outcome positive operator-valued measurements (POVMs). We show that measurement-based engines can outperform conventional quantum Otto engines within specific parameter regimes and that POVM-based engines can yield higher optimal work extraction than PVM-based ones. Furthermore, by incorporating the thermodynamic cost associated with resetting the auxiliary system required for POVM implementation, we demonstrate that the resulting net work output can still exceed that of PVM-based engines under suitable conditions on the spectral gaps and cold bath temperature. We also identify regimes in which non-adiabatic implementations can yield higher work output and efficiency than their adiabatic counterparts. Our study provides operational guidelines for designing improved measurement-driven quantum Otto engines.
The Markovian time evolution of the entropy production rate is studied as a measure of irreversibility generated in a bipartite quantum system consisting of two coupled bosonic modes immersed in a common thermal environment. The dynamics of the system is described in the framework of the formalism of the theory of open quantum systems based on completely positive quantum dynamical semigroups, for initial two-mode squeezed thermal states, squeezed vacuum states, thermal states and coherent states. We show that the rate of the entropy production of the initial state and nonequilibrium stationary state, and the time evolution of the rate of entropy production, strongly depend on the parameters of the initial Gaussian state (squeezing parameter and average thermal photon numbers), frequencies of modes, parameters characterising the thermal environment (temperature and dissipation coefficient), and the strength of coupling between the two modes. We also provide a comparison of the behaviour of entropy production rate and Rényi-2 mutual information present in the considered system.
In a classic thought experiment, Szilard suggested a heat engine where a single particle, for example an atom or a molecule, is confined in a container coupled to a single heat bath. The container can be separated into two parts by a moveable wall acting as a piston. In a single cycle of the engine, work can be extracted from the information on which side of the piston the particle resides. The work output is consistent with Landauers principle that the erasure of one bit of information costs the entropy kB ln 2, exemplifying the fundamental relation between work, heat and information. Here we apply the concept of the Szilard engine to a fully interacting quantum many-body system. We find that a working medium of a number of bosons (larger or equal two) with attractive interactions is clearly superior to other previously discussed setups. In sharp contrast to the classical case, we find that the average work output increases with the particle number. The highest overshoot occurs for a small but finite temperature, showing an intricate interplay between thermal and quantum effects. We anticipate that our finding will shed new light on the role of information in controlling thermodynamic fluctuations in the deep quantum regime, which are strongly influenced by quantum correlations in interacting systems.