scholarly journals Thermalization of small quantum systems: From the zeroth law of thermodynamics

2021 ◽  
Author(s):  
Jiaozi Wang ◽  
Wen-Ge Wang ◽  
Jiao Wang
Keyword(s):  
Quantum System ◽  
Chaotic Systems ◽  
Environmental Temperature ◽  
Quantum Systems ◽  
Necessary Condition ◽  
Environmental System ◽  
Small System ◽  
Composite Systems ◽  
Small Quantum

Abstract Thermalization of isolated quantum systems has been studied intensively in recent years and significant progresses have been achieved. Here, we study thermalization of small quantum systems that interact with large chaotic environments under the consideration of Schrödinger evolution of composite systems, from the perspective of the zeroth law of thermodynamics. Namely, we consider a small quantum system that is brought into contact with a large environmental system; after they have relaxed, they are separated and their temperatures are studied. Our question is under what conditions the small system may have a detectable temperature that is identical with the environmental temperature. This should be a necessary condition for the small quantum system to be thermalized and to have a well-defined temperature. By using a two-level probe quantum system that plays the role of a thermometer, we find that the zeroth law is applicable to quantum chaotic systems, but not to integrable systems.

scholarly journals Minimizing irreversible losses in quantum systems by local counterdiabatic driving

2017 ◽  
Vol 114 (20) ◽  
pp. E3909-E3916 ◽  
Author(s):  
Dries Sels ◽  
Anatoli Polkovnikov
Keyword(s):  
Variational Approach ◽  
Chaotic Systems ◽  
Chem Phys ◽  
Quantum Systems ◽  
Particle Systems ◽  
Coupling Constant ◽  
Quantum Annealing ◽  
Physical Constraints ◽  
Adiabatic Dynamics

Counterdiabatic driving protocols have been proposed [Demirplak M, Rice SA (2003) J Chem Phys A 107:9937–9945; Berry M (2009) J Phys A Math Theor 42:365303] as a means to make fast changes in the Hamiltonian without exciting transitions. Such driving in principle allows one to realize arbitrarily fast annealing protocols or implement fast dissipationless driving, circumventing standard adiabatic limitations requiring infinitesimally slow rates. These ideas were tested and used both experimentally and theoretically in small systems, but in larger chaotic systems, it is known that exact counterdiabatic protocols do not exist. In this work, we develop a simple variational approach allowing one to find the best possible counterdiabatic protocols given physical constraints, like locality. These protocols are easy to derive and implement both experimentally and numerically. We show that, using these approximate protocols, one can drastically suppress heating and increase fidelity of quantum annealing protocols in complex many-particle systems. In the fast limit, these protocols provide an effective dual description of adiabatic dynamics, where the coupling constant plays the role of time and the counterdiabatic term plays the role of the Hamiltonian.

scholarly journals Can small quantum systems learn

2017 ◽  
Vol 17 (7&8) ◽  
pp. 568-594
Author(s):  
Nathan Wiebe ◽  
Christopher Grandade
Keyword(s):  
Quantum Mechanics ◽  
Fault Tolerance ◽  
Bayesian Inference ◽  
Quantum System ◽  
Lower Bounds ◽  
State Vector ◽  
Quantum Systems ◽  
Posterior Distributions ◽  
Quantum Devices ◽  
Small Quantum

We examine the question of whether quantum mechanics places limitations on the ability of small quantum devices to learn. We specifically examine the question in the context of Bayesian inference, wherein the prior and posterior distributions are encoded in the quantum state vector. We conclude based on lower bounds from Grover’s search that an efficient blackbox method for updating the distribution is impossible. We then address this by providing a new adaptive form of approximate quantum Bayesian inference that is polynomially faster than its classical anolog and tractable if the quantum system is augmented with classical memory or if the low–order moments of the distribution are protected through redundant preparation. This work suggests that there may be a connection between fault tolerance and the capacity of a quantum system to learn from its surroundings.

scholarly journals The Renewed Role of Sweep Functions in Noisy Shortcuts to Adiabaticity

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 897
Author(s):  
Michele Delvecchio ◽  
Francesco Petiziol ◽  
Sandro Wimberger
Keyword(s):  
Quantum System ◽  
Quantum Systems ◽  
Shortcuts To Adiabaticity ◽  
Experimental Implementation ◽  
Free Case ◽  
Control Of Quantum Systems

We study the robustness of different sweep protocols for accelerated adiabaticity following in the presence of static errors and of dissipative and dephasing phenomena. While in the noise-free case, counterdiabatic driving is, by definition, insensitive to the form of the original sweep function, this property may be lost when the quantum system is open. We indeed observe that, according to the decay and dephasing channels investigated here, the performance of the system becomes highly dependent on the sweep function. Our findings are relevant for the experimental implementation of robust shortcuts-to-adiabaticity techniques for the control of quantum systems.

scholarly journals Más allá de la presuposición newtoniana: propiedades genuinamente disposicionales en la mecánica cuántica

1990 ◽  
Vol 22 (66) ◽  
pp. 25-37
Author(s):  
Sergio Martínez
Keyword(s):  
Quantum Mechanics ◽  
Quantum System ◽  
Physical System ◽  
Modern Science ◽  
Quantum Systems ◽  
Theoretical Modeling ◽  
Different Types ◽  
Modern Physics ◽  
Dispositional Properties

A central metaphysical thesis of modern science has been the idea that the structure of a physical system can be explained in terms of the properties of its constitutive subsystems. I call this presupposition the Newtonian merological presupposition. After some brief introductory remarks on the role of this presupposition in the methodology of modern physics, and after mentioning some recent challenges to it, I focus my attention on quantum systems. Quantum mechanics is the only highly confirmed theory in which the Newtonian merological presupposition is denied. I argue that the presence of a non-Newtonian (holistic) merological structure is the result of the existence of two different types of properties, and in particular of the existence of genuinely dispositional properties. Genuinely dispositional properties are properties of a system which are not reducible to occurrent properties of the subsystems. This distinction between two different types of properties can be made precise in a lattice theoretical modeling of the possible properties and states attributable to a quantum system. I conclude by giving an example of the sort of genuinely dispositional properties that are constitutive of quantum systems.

scholarly journals The geometry of passivity for quantum systems and a novel elementary derivation of the Gibbs state

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 411
Author(s):  
Nikolaos Koukoulekidis ◽  
Rhea Alexander ◽  
Thomas Hebdige ◽  
David Jennings
Keyword(s):  
Quantum System ◽  
Gibbs State ◽  
Quantum Systems ◽  
Passive State ◽  
Necessary Condition ◽  
Single Shot ◽  
Convex Shape ◽  
Geometric Measure ◽  
Manifold Of Equilibrium States ◽  
Simple Convex

Passivity is a fundamental concept that constitutes a necessary condition for any quantum system to attain thermodynamic equilibrium, and for a notion of temperature to emerge. While extensive work has been done that exploits this, the transition from passivity at a single-shot level to the completely passive Gibbs state is technically clear but lacks a good over-arching intuition. Here, we reformulate passivity for quantum systems in purely geometric terms. This description makes the emergence of the Gibbs state from passive states entirely transparent. Beyond clarifying existing results, it also provides novel analysis for non-equilibrium quantum systems. We show that, to every passive state, one can associate a simple convex shape in a 2-dimensional plane, and that the area of this shape measures the degree to which the system deviates from the manifold of equilibrium states. This provides a novel geometric measure of athermality with relations to both ergotropy and β--athermality.

scholarly journals Parts and Composites of Quantum Systems

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1031
Author(s):  
Stanley P. Gudder
Keyword(s):  
Tensor Product ◽  
Hilbert Spaces ◽  
Quantum Systems ◽  
Quantum Measurements ◽  
Quantum Channels ◽  
Measurement Models ◽  
Composite Systems ◽  
Finite Dimensional ◽  
Sequential Products

We consider three types of entities for quantum measurements. In order of generality, these types are observables, instruments and measurement models. If α and β are entities, we define what it means for α to be a part of β. This relationship is essentially equivalent to α being a function of β and in this case β can be employed to measure α. We then use the concept to define the coexistence of entities and study its properties. A crucial role is played by a map α^ which takes an entity of a certain type to one of a lower type. For example, if I is an instrument, then I^ is the unique observable measured by I. Composite systems are discussed next. These are constructed by taking the tensor product of the Hilbert spaces of the systems being combined. Composites of the three types of measurements and their parts are studied. Reductions in types to their local components are discussed. We also consider sequential products of measurements. Specific examples of Lüders, Kraus and trivial instruments are used to illustrate various concepts. We only consider finite-dimensional systems in this article. Finally, we mention the role of symmetry representations for groups using quantum channels.

The Temptations of Christ and Other Stories

2018 ◽  
Author(s):  
Eleonore Stump
Keyword(s):  
Human Person ◽  
Necessary Condition ◽  
Biblical Narratives ◽  
God's Love ◽  
The Way

This chapter examines biblical narratives to illuminate the role of Christ’s passion and death in bringing a person to a life in grace. Reflection on the narratives shows that Christ’s passion and death are a most promising way for God to help a human person to the surrender which is the necessary condition for spiritual and moral regeneration. The stories of the temptations of Christ show the way in which Christ’s suffering and death are connected to justification and sanctification. A person’s ceasing to resist the grace of God and surrendering to God’s love is the pinnacle on which her salvation has to stand. If we focus on this necessary condition for salvation, we can see the reason for Christ’s suffering. What can be gained by weakness that could not be gotten through power is the melting of a heart accustomed to willed loneliness and hardened against joy.

scholarly journals Tangible reduction in learning sample complexity with large classical samples and small quantum system

2021 ◽  
Vol 20 (8) ◽  
Author(s):  
Wooyeong Song ◽  
Marcin Wieśniak ◽  
Nana Liu ◽  
Marcin Pawłowski ◽  
Jinhyoung Lee ◽  
...  
Keyword(s):  
Quantum System ◽  
Learning Sample ◽  
Sample Complexity ◽  
Small Quantum

The role of environmental temperature on movement patterns of giant anteaters

2021 ◽  
Author(s):  
Aline GIROUX ◽  
Zaida ORTEGA ◽  
Alessandra BERTASSONI ◽  
Arnaud Léonard Jean DESBIEZ ◽  
Danilo KLUYBER ◽  
...  
Keyword(s):  
Environmental Temperature ◽  
Movement Patterns

scholarly journals Simulating molecules on a cloud-based 5-qubit IBM-Q universal quantum computer

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
S. Leontica ◽  
F. Tennie ◽  
T. Farrow
Keyword(s):  
Quantum System ◽  
Energy Transport ◽  
Quantum Computer ◽  
Complex Molecule ◽  
Dissipative System ◽  
Quantum Simulation ◽  
Quantum Systems ◽  
Molecular Structures ◽  
Unitary Evolution ◽  
Universal Quantum

AbstractSimulating the behaviour of complex quantum systems is impossible on classical supercomputers due to the exponential scaling of the number of quantum states with the number of particles in the simulated system. Quantum computers aim to break through this limit by using one quantum system to simulate another quantum system. Although in their infancy, they are a promising tool for applied fields seeking to simulate quantum interactions in complex atomic and molecular structures. Here, we show an efficient technique for transpiling the unitary evolution of quantum systems into the language of universal quantum computation using the IBM quantum computer and show that it is a viable tool for compiling near-term quantum simulation algorithms. We develop code that decomposes arbitrary 3-qubit gates and implement it in a quantum simulation first for a linear ordered chain to highlight the generality of the approach, and second, for a complex molecule. We choose the Fenna-Matthews-Olsen (FMO) photosynthetic protein because it has a well characterised Hamiltonian and presents a complex dissipative system coupled to a noisy environment that helps to improve the efficiency of energy transport. The method can be implemented in a broad range of molecular and other simulation settings.

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