Revisiting thermodynamics in computation and information theory

One of the primary motivations of the research in the field of computation is to optimize the cost of computation. The major ingredient that a computer needs is the energy to run a process, i.e., the thermodynamic cost. The analysis of the thermodynamic cost of computation is one of the prime focuses of research. It started back since the seminal work of Landauer where it was commented that the computer spends kB T ln2 amount of energy to erase a bit of information (here T is the temperature of the system and kB represents the Boltzmann's constant). The advancement of statistical mechanics has provided us the necessary tool to understand and analyze the thermodynamic cost for the complicated processes that exist in nature, even the computation of modern computers. The advancement of physics has helped us to understand the connection of the statistical mechanics (the thermodynamics cost) with computation. Another important factor that remains a matter of concern in the field of computer science is the error correction of the error that occurs while transmitting the information through a communication channel. Here in this article, we have reviewed the progress of the thermodynamics of computation starting from Landauer's principle to the latest model, which simulates the modern complex computation mechanism. After exploring the salient parts of computation in computer science theory and information theory, we have reviewed the thermodynamic cost of computation and error correction. We have also discussed about the alternative computation models that have been proposed with thermodynamically cost-efficient.Comment: Review article, 40 pages, 15 figures, comments are welcom

PT\mathcal{PT}-symmetric effects in measurement-based quantum thermal machines

Measurement-based quantum thermal machines are fascinating models of thermodynamic cycles where measurement protocols play an important role in the performance and functioning of the cycle. Despite theoretical advances, interesting experimental implementations have been reported. Here we move a step further by considering in this class of cycle $\mathcal{PT}$-symmetric non-Hermitian Hamiltonians and their implications in quantum thermal machines fueled by generalized measurements. We present theoretical results indicating that $\mathcal{PT}$-symmetric effects and measurement protocols are related along the cycle. Furthermore, tuning the parameters suitably it is possible to improve the power output (engine configuration) and the cooling rate (refrigerator configuration), operating in the Otto limit, in a finite-time cycle that satisfies the quantum adiabatic theorem. Our model also allows switching the configuration of the cycle, engine, or refrigerator, depending on the strength of the measurement protocol

Binary Black Hole Information Loss Paradox & Future Prospects

Various techniques to tackle the black hole information paradox have been proposed. A new way out to tackle the paradox is via the use of a pseudo-density operator. This approach has successfully dealt with the problem with a two qubit entangle system for a single black hole. In this paper, we present the interaction with a binary black hole system by using an arrangement of the three qubit system of Greenberger Horne Zeilinger (GHZ) state. We show that our results are in excellent agreement with the theoretical value. We have also studied the interaction between the two black holes by considering the correlation between the qubits in the binary black hole system. The results depict a complete agreement with the proposed model. In addition to the verification, we also propose how modern detection of gravitational waves can be used on our optical setup as an input source, thus bridging the gap with the gravitational wave's observational resources in terms of studying black hole properties with respect to quantum information and entanglement

Many-body quantum thermal machines in a Lieb-kagome Hubbard model

Quantum many-body systems serve as a suitable working medium for realizing quantum thermal machines (QTMs) by offering distinct advantages such as cooperative many-body effects, and performance boost at the quantum critical points. However, the bulk of the existing literature exploring the criticality of many-body systems in the context of QTMs involves models sans the electronic interactions, which are non-trivial to deal with and require sophisticated numerical techniques. Here we adopt the prototypical Hubbard model in two dimensions (2D) in the framework of the line graph Lieb-kagome lattice for the working medium of a multi-functional QTM. We resort to a non-perturbative, static path approximated (SPA) Monte Carlo technique to deal with the repulsive Hubbard model. We observe that in a Stirling cycle, in both the interacting and non-interacting limits, the heat engine function dominates and its performance gets better when the strain is induced from the kagome to the Lieb limit, while for the reverse the refrigeration action is preferred. Further, we show that the QTM performs better when the difference between the temperatures of the two baths is lower and the QTM reaches the Carnot limit in this regime. Further, we extensively study the performance of the QTM in the repulsive Hubbard interacting regime where the magnetic orders come into the picture. We explore the performance of the QTM along the quantum critical points and in the large interaction limit.Comment: Preliminary draft, comments welcome