scholarly journals Measurement Based Quantum Heat Engine with Coupled Working Medium

Entropy ◽  
2019 ◽  
Vol 21 (11) ◽  
pp. 1131 ◽  
Author(s):  
Arpan Das ◽  
Sibasish Ghosh
Keyword(s):  
Heat Engine ◽  
Coupling Constants ◽  
Cyclic Process ◽  
Coupling Constant ◽  
Quantum Heat Engine ◽  
Working Medium ◽  
Single Temperature ◽  
Higher Spin ◽  
Higher Spins ◽  
The Relationship

We consider measurement based single temperature quantum heat engine without feedback control, introduced recently by Yi, Talkner and Kim [Phys. Rev. E 96, 022108 (2017)]. Taking the working medium of the engine to be a one-dimensional Heisenberg model of two spins, we calculate the efficiency of the engine undergoing a cyclic process. Starting with two spin-1/2 particles, we investigate the scenario of higher spins also. We show that, for this model of coupled working medium, efficiency can be higher than that of an uncoupled one. However, the relationship between the coupling constant and the efficiency of the engine is rather involved. We find that in the higher spin scenario efficiency can sometimes be negative (this means work has to be done to run the engine cycle) for certain range of coupling constants, in contrast to the aforesaid work of Yi, Talkner and Kim, where they showed that the extracted work is always positive in the absence of coupling. We provide arguments for this negative efficiency in higher spin scenarios. Interestingly, this happens only in the asymmetric scenarios, where the two spins are different. Given these facts, for judiciously chosen conditions, an engine with coupled working medium gives advantage for the efficiency over the uncoupled one.

The relationship between carbon-13 substituent chemical shifts and proton coupling constants in aza-aromatic systems

1984 ◽  
Vol 37 (2) ◽  
pp. 311 ◽  
Author(s):  
IB Cook ◽  
S Pengprecha ◽  
B Ternai
Keyword(s):  
Experimental Data ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Proton Proton ◽  
Proton Coupling ◽  
Substituted Pyridines ◽  
Aromatic Systems ◽  
The Relationship

An equation which relates the ortho carbon-13 substituent chemical shift α-SCS in aza-aromatics to the ortho proton-proton coupling constant 3J(HH) in the corresponding carbocyclic compound is derived from experimental data. The implications for N-N bond fixation in diaza-aromatics are discussed. When the equation is applied to 2-substituted pyridines, an electronegativity parameter must be included to explain the results.

scholarly journals An interaction-driven many-particle quantum heat engine and its universal behavior

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Yang-Yang Chen ◽  
Gentaro Watanabe ◽  
Yi-Cong Yu ◽  
Xi-Wen Guan ◽  
Adolfo del Campo
Keyword(s):  
Low Temperatures ◽  
Degrees Of Freedom ◽  
Heat Engine ◽  
Interaction Strength ◽  
Luttinger Liquid ◽  
Heating And Cooling ◽  
Quantum Heat Engine ◽  
Working Medium ◽  
Average Work ◽  
Isochoric Heating

Abstract A quantum heat engine (QHE) based on the interaction driving of a many-particle working medium is introduced. The cycle alternates isochoric heating and cooling strokes with both interaction-driven processes that are simultaneously isochoric and isentropic. When the working substance is confined in a tight waveguide, the efficiency of the cycle becomes universal at low temperatures and governed by the ratio of velocities of a Luttinger liquid. We demonstrate the performance of the engine with an interacting Bose gas as a working medium and show that the average work per particle is maximum at criticality. We further discuss a work outcoupling mechanism based on the dependence of the interaction strength on the external spin degrees of freedom.

scholarly journals Bound on Efficiency of Heat Engine from Uncertainty Relation Viewpoint

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 439
Author(s):  
Pritam Chattopadhyay ◽  
Ayan Mitra ◽  
Goutam Paul ◽  
Vasilios Zarikas
Keyword(s):  
Uncertainty Relation ◽  
Heat Engine ◽  
Upper And Lower Bounds ◽  
Engine Model ◽  
Heat Engines ◽  
Quantum Heat Engine ◽  
Quantum Observables ◽  
Thermodynamic Variables ◽  
Work Done ◽  
The Relationship

Quantum cycles in established heat engines can be modeled with various quantum systems as working substances. For example, a heat engine can be modeled with an infinite potential well as the working substance to determine the efficiency and work done. However, in this method, the relationship between the quantum observables and the physically measurable parameters—i.e., the efficiency and work done—is not well understood from the quantum mechanics approach. A detailed analysis is needed to link the thermodynamic variables (on which the efficiency and work done depends) with the uncertainty principle for better understanding. Here, we present the connection of the sum uncertainty relation of position and momentum operators with thermodynamic variables in the quantum heat engine model. We are able to determine the upper and lower bounds on the efficiency of the heat engine through the uncertainty relation.

scholarly journals Superadiabatic quantum heat engine with a multiferroic working medium

2016 ◽  
Vol 94 (3) ◽  
Author(s):  
L. Chotorlishvili ◽  
M. Azimi ◽  
S. Stagraczyński ◽  
Z. Toklikishvili ◽  
M. Schüler ◽  
...  
Keyword(s):  
Heat Engine ◽  
Quantum Heat Engine ◽  
Working Medium

scholarly journals Bound on Efficiency of Heat Engine From Uncertainty Relation Viewpoint

2021 ◽  
Author(s):  
Ayan Mitra ◽  
Pritam Chattapadhyay ◽  
Goutam Paul ◽  
Vasilios Zarikas
Keyword(s):  
Uncertainty Relation ◽  
Heat Engine ◽  
Upper And Lower Bounds ◽  
Engine Model ◽  
Heat Engines ◽  
Quantum Heat Engine ◽  
Quantum Observables ◽  
Thermodynamic Variables ◽  
Work Done ◽  
The Relationship

Abstract Quantum cycles in established heat engines can be modeled with various quantum systems as working substances. As for example, heat engine can be modeled with an infinite potential well as the working substance to determine the efficiency and work done. However, in this method, the relationship between the quantum observables and the physically measurable parameters, i.e., the efficiency and work done is not well understood from the quantum mechanics approach. A detailed analysis is needed to link the thermodynamical variables (on which the efficiency and work done depends) with the uncertainty principle for better understanding. Here, we present the connection of sum uncertainty relation of position and momentum operators with thermodynamic variables in the quantum heat engine model. We are able to determine the upper and lower bounds on the efficiency of the heat engine through uncertainty relation.

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Function Calculations

2019 ◽  
Author(s):  
Xianghai Sheng ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Density Functional Theory ◽  
Exchange Coupling ◽  
Density Functional ◽  
Spin Crossover ◽  
Coupling Constants ◽  
Spin Projection ◽  
Coupling Constant ◽  
Projection Model ◽  
Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

Processes and Responses

2017 ◽  
Author(s):  
Jochen Rau
Keyword(s):  
Heat Engine ◽  
Cyclic Process ◽  
Free Enthalpy ◽  
Initial State ◽  
Thermodynamic Potentials ◽  
Grand Potential ◽  
Laws Of Thermodynamics ◽  
Cyclic Processes ◽  
Energy Exchanges ◽  
Thermodynamic Processes

Thermodynamic processes involve energy exchanges in the forms of work, heat, or particles. Such exchanges might be reversible or irreversible, and they might be controlled by barriers or reservoirs. A cyclic process takes a system through several states and eventually back to its initial state; it may convert heat into work (engine) or vice versa (heat pump). This chapter defines work and heat mathematically and investigates their respective properties, in particular their impact on entropy. It discusses the roles of barriers and reservoirs and introduces cyclic processes. Basic constraints imposed by the laws of thermodynamics are considered, in particular on the efficiency of a heat engine. The chapter also introduces the thermodynamic potentials: free energy, enthalpy, free enthalpy, and grand potential. These are used to describe energy exchanges and equilibrium in the presence of reservoirs. Finally, this chapter considers thermodynamic coefficients which characterize the response of a system to heating, compression, and other external actions.

scholarly journals The 3d $$ \mathcal{N} $$ = 6 bootstrap: from higher spins to strings to membranes

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Damon J. Binder ◽  
Shai M. Chester ◽  
Max Jerdee ◽  
Silviu S. Pufu
Keyword(s):  
Block Decomposition ◽  
Point Function ◽  
Present Evidence ◽  
Bootstrap Techniques ◽  
Wide Range ◽  
Higher Spin ◽  
Tensor Multiplet ◽  
Higher Spins ◽  
M Theory ◽  
Chern Simons

Abstract We study the space of 3d $$ \mathcal{N} $$ N = 6 SCFTs by combining numerical bootstrap techniques with exact results derived using supersymmetric localization. First we derive the superconformal block decomposition of the four-point function of the stress tensor multiplet superconformal primary. We then use supersymmetric localization results for the $$ \mathcal{N} $$ N = 6 U(N)k × U(N + M)−k Chern-Simons-matter theories to determine two protected OPE coefficients for many values of N, M, k. These two exact inputs are combined with the numerical bootstrap to compute precise rigorous islands for a wide range of N, k at M = 0, so that we can non-perturbatively interpolate between SCFTs with M-theory duals at small k and string theory duals at large k. We also present evidence that the localization results for the U(1)2M × U (1 + M)−2M theory, which has a vector-like large-M limit dual to higher spin theory, saturates the bootstrap bounds for certain protected CFT data. The extremal functional allows us to then conjecturally reconstruct low-lying CFT data for this theory.

scholarly journals Quantum control of excitons for reversible heat transfer

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Conor N. Murphy ◽  
Paul R. Eastham
Keyword(s):  
Heat Transfer ◽  
Quantum Dot ◽  
Quantum Control ◽  
Heat Engine ◽  
Laser Pulses ◽  
Heat Current ◽  
Light Emitting ◽  
Laser Dressing ◽  
Working Medium ◽  
Heat Transfers

Abstract Lasers, photovoltaics, and thermoelectrically-pumped light emitting diodes are thermodynamic machines which use excitons (electron-hole pairs) as the working medium. The heat transfers in such devices are highly irreversible, leading to low efficiencies. Here we predict that reversible heat transfers between a quantum-dot exciton and its phonon environment can be induced by laser pulses. We calculate the heat transfer when a quantum-dot exciton is driven by a chirped laser pulse. The reversibility of this heat transfer is quantified by the efficiency of a heat engine in which it forms the hot stroke, which we predict to reach 95% of the Carnot limit. This performance is achieved by using the time-dependent laser-dressing of the exciton to control the heat current and exciton temperature. We conclude that reversible heat transfers can be achieved in excitonic thermal machines, allowing substantial improvements in their efficiency.

Practical implementation of aCO2-laser-coupled quantum heat engine

2005 ◽  
Vol 72 (4) ◽  
Author(s):  
Alan E. Hill ◽  
Yuri V. Rostovtsev ◽  
Marlan O. Scully
Keyword(s):  
Heat Engine ◽  
Practical Implementation ◽  
Quantum Heat Engine
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