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Register a new userRefined Definitions of Heat and Work in Quantum Thermodynamics
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In this paper, unambiguous redefinitions of heat and work are presented for quantum thermodynamic systems. We will use genuine reasoning based on which Clausius originally defined work and heat in establishing thermodynamics. The change in the energy which is accompanied by a change in the entropy is identified as heat, while any change in the energy which does not lead to a change in the entropy is known as work. It will be seen that quantum coherence does not allow all the energy exchanged between two quantum systems to be only of the heat form. Several examples will also be discussed. Finally, it will be shown that these refined definitions will strongly affect the entropy production of quantum thermodynamic processes giving new insight into the irreversibility of quantum processes.
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We analyze the new redefinitions of heat Q and work W recently presented in [arXiv: 1912.01939; arXiv:1912.01983v5] in the quantum thermodynamics domain. According to these redefinitions, heat must be associated with the variation of entropy, while work must be associated with variation of state vectors. Analyzing the behavior of two specific examples, we show some peculiarities of these new redefinitions which, based on the counterexample presented, seems to point to a possible inadequacy of these redefinitions.
Quantum thermodynamics and quantum information are two frameworks for employing quantum mechanical systems for practical tasks, exploiting genuine quantum features to obtain advantages with respect to classical implementations. While appearing disconnected at first, the main resources of these frameworks, work and correlations, have a complicated yet interesting relationship that we examine here. We review the role of correlations in quantum thermodynamics, with a particular focus on the conversion of work into correlations. We provide new insights into the fundamental work cost of correlations and the existence of optimally correlating unitaries, and discuss relevant open problems.
We analyze the role of indirect quantum measurements in work extraction from quantum systems in nonequilibrium states. In particular, we focus on the work that can be obtained by exploiting the correlations shared between the system of interest and an additional ancilla, where measurement backaction introduces a nontrivial thermodynamic tradeoff. We present optimal state-dependent protocols for extracting work from both classical and quantum correlations, the latter being measured by discord. We show that, while the work content of classical correlations can be fully extracted by performing local operations on the system of interest, the amount of work related to quantum discord requires a specific driving protocol that includes interaction between system and ancilla.
Despite the increasing interest, the research field which studies the concepts of work and heat at quantum level has suffered from two main drawbacks: first, the difficulty to properly define and measure the work, heat and internal energy variation in a quantum system and, second, the lack of experiments. Here, we report a full characterization of the dissipated heat, work and internal energy variation in a two-level quantum system interacting with an engineered environment. We use the IBMQ quantum computer to implement the driven systems dynamics in a dissipative environment. The experimental data allow us to construct quasi-probability distribution functions from which we recover the correct averages of work, heat and internal energy variation in the dissipative processes. Interestingly, by increasing the environment coupling strength, we observe a reduction of the pure quantum features of the energy exchange processes that we interpret as the emergence of the classical limit. This makes the present approach a privileged tool to study, understand and exploit quantum effects in energy exchanges.
Quantum technology is an emergent area with the potential to be disruptive and ability to affect many human activities. Quantum technologies are dual-use technologies, and as such, they are the subject of interest for the defence and security industry and military and governmental actors. This report aims to review and map the possible quantum technology military applications to serve as the entry point for international peace and international security assessment, ethics research or military and governmental policy, strategy and decision making. Quantum technologies for military applications, introducing new capabilities, increasing effectiveness and improving precision lead to quantum warfare, wherein new military strategies, doctrines, policies and ethics should be established. This report provides a basic overview of quantum technologies under development where the expected time scale of delivery or utilisation impact are estimated. The particular applications of quantum technology for the military are described for various warfare domains (e.g., cyber, space, electronic, underwater warfare, or intelligence, surveillance, target acquisition, and reconnaissance), and related issues and challenges are articulated.
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