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We introduce the resource-theoretic free energy of a quantum channel as the maximal work extractable from the channel as its output equilibrates to a thermal state and its reference system remains locally intact. It is proportional to the…

Quantum Physics · Physics 2025-10-29 Himanshu Badhani , Dhanuja G S , Siddhartha Das

Characterizing quantum processes is indispensable for the implementation of any task in quantum information processing. In this paper, we develop an efficient method to fully characterize arbitrary Gaussian processes in continuous-variable…

Quantum Physics · Physics 2025-09-05 Logan W. Grove , Pratik J. Barge , Kevin Valson Jacob

The quantum measurement problem is revisited and discussed in terms of a new solvable measurement model which basic ingredient is the quantum model of a controlled single-bit memory. The structure of this model involving strongly coupled…

Quantum Physics · Physics 2013-05-22 Robert Alicki

In the conventional two-point measurement scheme of quantum thermodynamics, quantum coherence is destroyed by the first measurement. But as we know the coherence really plays an important role in the quantum thermodynamics process, and how…

Quantum Physics · Physics 2018-05-30 Bao-Ming Xu , Jian Zou , Li-Sha Guo , Xiang-Mu Kong

In this article we derive a useful expectation identity using the language of quantum statistical mechanics, where density matrices represent the state of knowledge about the system. This identity allows to establish relations between…

Quantum Physics · Physics 2024-10-29 Boris Maulén , Sergio Davis , Daniel Pons

We study the achievements of quantum circuits comprised of several one- and two-qubit gates. Quantum process matrices are determined for the basic one- and two-qubit gate operations and concatenated to yield the process matrix of the…

Quantum Physics · Physics 2014-04-11 J. Gulliksen , D. D. Bhaktavatsala Rao , K. Mølmer

The paradox of Maxwell's demon motivated the development of information thermodynamics and the creation of nanoscale information engines. We now understand that machines such as the molecular motors within cells can in principle harvest…

Non-equilibrium quantum thermodynamics is essential to describe new devices that operate far from the regime where the usual thermodynamical laws are obeyed. When quantum fluctuations dominate, defining and measuring work and heat, two…

Subsystems of a composite system in a pure state generally exist in mixed states and undergo changes with the overall state. This phenomenon arises from the coherence of the entire system and represents a crucial distinction between quantum…

Quantum Physics · Physics 2024-04-04 Zi-Yan Zhang , Jian-Ying Du , Fu-Lin Zhang

Quantum measurements can inject energy into quantum systems, enabling engines whose operation is powered entirely by measurements. We develop a general theory of quantum vacuum measurement engines by introducing the quantum vacuum bending…

Quantum Physics · Physics 2026-02-04 Robert Czupryniak , Bibek Bhandari , Paolo Andrea Erdman , Andrew N Jordan

Thermal channels -- the free processes allowed in the resource theory of quantum thermodynamics -- are generalised to thermal instruments, which we interpret as implementing thermodynamically free quantum measurements; a Maxwellian demon…

Quantum Physics · Physics 2023-01-04 M. Hamed Mohammady

We consider the role of quantum correlations in the efficient use of information by a predictive quantum system, generalizing a recently proposed classical measure of non-predictive information to the quantum regime. We show that, as a…

Quantum Physics · Physics 2014-08-27 Arne L. Grimsmo

Recent advances in experimental techniques allow one to measure and control systems at the level of single molecules and atoms. Here gaining information about fluctuating thermodynamic quantities is crucial for understanding nonequilibrium…

Statistical Mechanics · Physics 2019-05-01 Ken Funo , Masahito Ueda , Takahiro Sagawa

With the approaching second quantum revolution, the study of quantum thermodynamics, particularly heat flow, has become even more relevant for two main reasons. First, understanding heat and other types of noise is essential for protecting…

Quantum Physics · Physics 2024-01-25 Kasper Poulsen

Differential geometry offers a powerful framework for optimising and characterising finite-time thermodynamic processes, both classical and quantum. Here, we start by a pedagogical introduction to the notion of thermodynamic length. We…

Quantum Physics · Physics 2021-08-31 Paolo Abiuso , Harry J. D. Miller , Martí Perarnau-Llobet , Matteo Scandi

We demonstrate complete characterization of a two-qubit entangling process - a linear optics controlled-NOT gate operating with coincident detection - by quantum process tomography. We use maximum-likelihood estimation to convert the…

Quantum Physics · Physics 2008-11-26 J. L. O'Brien , G. J. Pryde , A. Gilchrist , D. F. V. James , N. K. Langford , T. C. Ralph , A. G. White

The act of describing how a physical process changes a system is the basis for understanding observed phenomena. For quantum-mechanical processes in particular, the affect of processes on quantum states profoundly advances our knowledge of…

Quantum Physics · Physics 2017-10-20 Jen-Hsiang Hsieh , Shih-Hsuan Chen , Che-Ming Li

In quantum systems which satisfy the hypothesis of equal weights for eigenstates [4], the maximum work principle (for extremely slow and relatively fast operation) is derived by using quantum dynamics alone. This may be a crucial step in…

Statistical Mechanics · Physics 2007-05-23 Hal Tasaki

Quantum processes, such as quantum circuits, quantum memories, and quantum channels, are essential ingredients in almost all quantum information processing tasks. However, the characterization of these processes remains a daunting task due…

Quantum Physics · Physics 2020-04-16 Ye-Chao Liu , Jiangwei Shang , Xiao-Dong Yu , Xiangdong Zhang

We present a description of the measurement process based on the parametric representation with environmental coherent states. This representation is specifically tailored for studying quantum systems whose environment needs being…

Quantum Physics · Physics 2015-09-30 Pietro Liuzzo-Scorpo , Alessandro Cuccoli , Paola Verrucchi