Classical Bath Research Articles

Dephasing dynamics of a central spin interacting with a classical Ising spin bath

We study the effect of interaction between bath spins on central spin dynamics. For this end, we consider various types of interactions among the bath fluctuators. We give an analytical relation for the dephasing dynamics of a central spin homogeneously interacting with a bath of classically interacting spins in thermal equilibrium. The obtained exact relation for the central spin dynamics depends on the average of the number of bath spins N in the canonical ensemble. We find the relation of dephasing time with bath's temperature and strength of interaction between bath spins. We show that if the classically interacting bath is large enough, off-diagonal coherence will decay into Gaussian form. This Gaussian decay is valid for temperatures higher than critical temperature. Moreover, we analytically prove the equivalence of dephasing dynamics for central spin models with classical Ising spin bath and quantum flip-flop spin bath interactions. Therefore, the dephasing dynamics for central spin models with quantum spin bath interactions can be reproduced with much less expensive classical spin bath interaction model instead. Our results can be applied in a number of quantum systems used in quantum sensing such as color centers in solids or quantum dots manuscript.

First-principles study of non-linear thermal expansion in cadmium titanate by molecular dynamics incorporating nuclear quantum effects

First-principles molecular dynamics (FPMD) simulations were applied for analyzing structural evolutions around the paraelectric-ferroelectric phase transition temperature in the perovskite-type cadmium titanate, CdTiO3. Since the phase transition is reported to occur at the low temperature around 80 K, the quantum thermal bath (QTB) method was utilized in this study, which incorporates the nuclear quantum effects (NQEs). The structural evolutions in the QTB-FPMD simulations are in reasonable agreement with the experimental results, by contrast in the conventional FPMD simulations using the classical thermal bath (CTB-FPMD). Especially, the non-linear thermal expansion of lattice constants around the phase transition temperature was well reproduced in the QTB-FPMD with the NQEs. Thus, the NQEs are of importance in phase transitions at low temperatures, particularly below the room temperature, and the QTB is useful in that it incorporates the NQEs in MD simulations with low computational costs comparable to the conventional CTB.

Powering quantum Otto engines only with q-deformation of the working substance.

We consider a quantum Otto cycle with a q-deformed quantum oscillator working substance and classical thermal baths. We investigate the influence of the quantum statistical deformation parameter q on the work and efficiency of the cycle. In usual quantum Otto cycle, a Hamiltonian parameter is varied during the quantum adiabatic stages while the quantum statistical character of the working substance remains fixed. We point out that even if the Hamiltonian parameters are not changing, work can be harvested by quantum statistical changes of the working substance. Work extraction from thermal resources using quantum statistical mutations of the working substance makes a quantum Otto cycle without any classical analog.

Single-atom exploration of optimized nonequilibrium quantum thermodynamics by reinforcement learning

Exploring optimized processes of thermodynamics at microscale is vital to exploitation of quantum advantages relevant to microscopic machines and quantum information processing. Here, we experimentally execute a reinforcement learning strategy, using a single trapped 40Ca+ ion, for engineering quantum state evolution out of thermal equilibrium. We consider a qubit system coupled to classical and quantum baths, respectively, the former of which is achieved by switching on the spontaneous emission relevant to the qubit and the latter of which is made based on a Jaynes-Cummings model involving the qubit and the vibrational degree of freedom of the ion. Our optimized operations make use of the external control on the qubit, designed by the reinforcement learning approach. In comparison to the conventional situation of free evolution subject to the same Hamiltonian of interest, our experimental implementation presents the evolution of the states with higher fidelity while with less consumption of entropy production and work, highlighting the potential of reinforcement learning in accomplishment of optimized nonequilibrium thermodynamic processes at atomic level.

Real-Time Dynamics and Detailed Balance in Ring Polymer Surface Hopping: The Impact of Frustrated Hops.

Ring polymer surface hopping (RPSH) has been recently introduced as a well-tailored method for incorporating nuclear quantum effects, such as zero-point energy and tunneling, into nonadiabatic molecular dynamics simulations. The practical widespread usage of RPSH demands a comprehensive benchmarking of different reaction regimes and conditions with equal emphasis on demonstrating both the cons and the pros of the method. Here, we investigate the fundamental questions related to the conservation of energy and detailed balance in the context of RPSH. Using Tully's avoided crossing model as well as a 2-state quantum system coupled to a classical bath undergoing Langevin dynamics, we probe the critical problem of the proper treatment of the classically forbidden transitions stemming from the surface hopping algorithm. We show that proper treatment of these frustrated hops is key to the accurate description of real-time dynamics as well as reproducing the correct quantum Boltzmann populations.

Experimental Access to Mode-Specific Coupling between Quantum Molecular Vibrations and Classical Bath Modes.

The interaction of quantum-mechanical systems with a fluctuating thermal environment (bath) is fundamental to molecular mechanics and energy transport/dissipation. Its complete picture requires mode-specific measurements of this interaction and an understanding of its nature. Here, we present a combined experimental and theoretical study providing detailed insights into the coupling between a high-frequency vibrational two-level system and thermally excited terahertz modes. Experimentally, two-dimensional terahertz-infrared-visible spectroscopy reports directly on the coupling between quantum oscillators represented by CH3 streching vibrations in liquid dimethyl sulfoxide and distinct low-frequency modes. Theoretically, we present a mixed quantum-classical formalism of the sample response to enable the simultaneous quantum description of high-frequency oscillators and a classical description of the bath. We derive the strength and nature of interaction and find different coupling between CH3 stretch and low-frequency modes. This general approach enables quantitative and mode-specific analysis of coupled quantum and classical dynamics in complex chemical systems.

Microwave-assisted extraction optimization and conventional extraction of phenolic compounds from coriander leaves: UHPLC characterization and antioxidant activity

Background: Qualitative and quantitative investigations of bioactive compounds in plant materials are heavily based on the selection of an accurate extraction method. Aims: That’s why; this work consists of a comparative study between Microwave Assisted Extraction (MAE) and Conventional Extraction (CE), based on the total phenolic compounds (TPC) yield, phenolic profile, and antioxidant activity of coriander leaves powder (Coriandrum sativum L.). Material and Methods: MAE was optimized and performed using the Response Surface Methodology (RSM), and was modeled by using a second-order regression equation. While CE was done using the classic water bath method. Results: Under the optimal conditions, the recovery of TPC yield obtained was 37.94 ± 2.06 mg (MAE) vs 44.47 ± 0.57 mg GAE/g DW (CE). The UHPLC characterization showed a close phenolic composition of the two extracts, mainly represented by quercetin glucosides and by dimethoxycinnamoyl hexoside. No significant difference (p>0.05) was recorded in terms of the antioxidant activity of both extracts, as estimated by Ferric reducing antioxidant power (FRAP), Nitric oxide (NO•), and superoxide anion (O2•-) scavenging tests. Conclusions: Hence, the exploitation of MAE has many valuable advantages, as the processing time is brief and the antioxidant activities and phenolic composition were not affected by the extraction process.

First-order transitions in spin chains coupled to quantum baths

We show that tailoring the dissipative environment allows us to change the features of continuous quantum phase transitions and even induce first-order transitions in ferromagnetic spin chains. In particular, using a numerically exact quantum Monte Carlo method for the paradigmatic Ising chain of one-half spins in a transverse magnetic field, we find that spin couplings to local quantum boson baths (in the Ohmic regime) can drive the transition from the second to the first order even for a low dissipation strength. Moreover, using a variational mean-field approach for the treatment of spin-spin and spin-boson interactions, we point out that phase discontinuities are ascribable to a dissipation-induced effective magnetic field which is intrinsically related to the bath quantum fluctuations and vanishes for classical baths. The effective field is able to switch the sign of the magnetization along the direction of spin-spin interactions. The results can be potentially tested in recent quantum simulators and are relevant for quantum sensing since the spin system could not only detect the properties of nonclassical baths, but also the effects of weak magnetic fields.

Samples of Kalemişi Work of the Çinili Bath Restoration with Zeyrek

Zeyrek Çinili Hamam, mimarisi, geleneksel ısınma sistemi ve süsleme elemanları
 açısından önem arz eden çifte bir hamamdır. 2010 yılında başlanan Çinili Hamam Koruma-
 Onarım ve Rehabilitasyon Projesi sonucunda yapının hamam işlevi ve ortaya çıkan
 kalemişleri korunacaktır.
 Barbaros Hayrettin Paşa’nın İstanbul’da tesis ettiği evkafına gelir getirmesi amacıyla
 bu yapı inşa edilmiştir. Zeyrek Çinili Hamam’ın bir inşa veya ihya kitâbesi olmamasına
 rağmen, Hassa Başmimarı Sinan tarafından inşa edildiği konusunda bir tereddüt bulunmamaktadır.
 Mimar Sinan’ın yaptığı yapıların listesini veren tezkirelerde ve Barbaros
 Hayrettin Paşa’nın vakfiyesinde hamamın adı geçmektedir. Mimar Sinan, Türk klasik
 hamamlarının temel ilkelerine bağlı kalmak koşuluyla, hamam mimarisi plan şemasında
 her zaman yeni arayışlar içinde olmuştur.
 Restorasyon çalışmaları sonucunda hamamın erkekler ve kadınlara ait soyunmalık
 kısımlarında yapıya ayrı bir boyut kazandıran kalemişleri gün ışığına çıkarılmıştır. Cibali
 yangınları sonrasında gerçekleşen onarımlarda yapılan ilk katman kalemişleri 1850
 senelerine aittir. Günümüze ulaşan en nitelikli kalemişleri ise 1850-1890 yılları arasına tarihlenir. 19. yüzyıla tarihlenen ve iki dönem şeklinde uygulanan kalemişleri bu makale
 ile ilk kez literatüre kazandırılmaktadır. Alt bölümlerin bezemeleri birbiri üstüne uygulanmış
 katmanlar halinde iken duvarların üst bölümlerinde ve kubbe geçişinde yer alan
 siyah-beyaz kalemişi ise tek katman halindedir. Klasik Dönem yapılarına 19. yüzyılda
 eklenen kalemişleri ile bu bezemeler arasında karşılaştırma yapılarak, benzerlikler örnekleri
 ile ortaya konulmuştur.

Energy conductance across a mesoscopic junction in a nonequilibrium spin-boson model under the influence of telegraph noise.

A spin-boson model in the presence of a telegraph noise (TN) source is employed to calculate the energy conductance between a tunnel junction and two bosonic baths. A polaron-transformed coupling term with the bosonic baths allows for treating quantum damping to arbitrary orders of strength. However, the polaron transformation yields a dressed tunneling frequency which is assumed small and treated perturbatively as is familiar in the noninteracting blip approximation in the context of the nonequilibrium spin-boson model. While the coupling with the bosonic baths leads to decoherence in an otherwise coherent tunneling process, the TN induces a different kind of fluctuation, that is, in the asymmetry of the underlying two-level system. It is the interplay of these two different relaxation effects, one triggered by the two quantum (bosonic) baths and the other through a classical bath (creating a TN), that is investigated here in detail. The TN that mimics the classical, fluctuating environment makes a nontrivial contribution to the self-energy that helps compute the imaginary part of the spin susceptibility which, in turn, determines the energy transfer across the junction. The range of validity of the TN is clarified at the outset and its efficacy in tuning the environmental influence is pointed out. The present paper complements an earlier similar study-albeit for fermionic baths-and provides additional input in terms of the TN to a previous investigation of energy transfer between a nanojunction and bosonic reservoirs without, however, the noisy environment.

Electronic dephasing in mixed quantum–classical molecular systems using the spin-boson model

Pure electronic dephasing is investigated using the spin-boson Hamiltonian in mixed quantum–classical environment. The spin-boson model used here is a composite system made up of a quantum subsystem, an electronic 2-level subsystem linearly coupled to harmonic vibrations, interacting with a classical bath. Experimental results for a multitude of molecular systems indicate that the zero-phonon line (ZPL) profile is determined by electronic dephasing, which is not accounted for in the multimode Brownian oscillator (MBO) model due to the unphysical contribution from the MBO bath modes to the ZPL profile. Mixed quantum–classical dynamics formalism of non-equilibrium systems is employed to assess the contribution of the bath modes to pure electronic dephasing by probing the ZPL profile when coupled to a classical bath in the mixed quantum–classical condensed systems. Pure electronic dephasing is discussed in the context of mixed quantum–classical dynamics formalism which starts with mixed quantum–classical Liouville equation in a mixed quantum–classical environment. It is noteworthy, however, that the fundamental difference between the fully quantum MBO model and the mixed quantum–classical Brownian oscillator, is that the zero-phonon line calculated by the former shows unphysical asymmetry on the low-energy side as it has not been observed in real systems, whereas the ZPL reported herein eliminates this asymmetry. A systematic approach using matrix mechanics is developed to treat this phenomenon. To this end, a closed-form expression of linear and nonlinear optical electronic transition dipole moment time correlation functions in a dissipative media are derived. Linear absorption spectra and 4-wave mixing signals at various temperatures showing a sound thermal broadening, temporal decay, and accurate pure dephasing further ratify the applicability and correctness of the mixed quantum–classical dynamics approach to spectroscopy and dynamics are computed.

Quantum bath effects on nonequilibrium heat transport in model molecular junctions.

Quantum-classical dynamics simulations enable the study of nonequilibrium heat transport in realistic models of molecules coupled to thermal baths. In these simulations, the initial conditions of the bath degrees of freedom are typically sampled from classical distributions. Herein, we investigate the effects of sampling the initial conditions of the thermal baths from quantum and classical distributions on the steady-state heat current in the nonequilibrium spin-boson model-a prototypical model of a single-molecule junction-in different parameter regimes. For a broad range of parameter regimes considered, we find that the steady-state heat currents are ∼1.3-4.5 times larger with the classical bath sampling than with the quantum bath sampling. Using both types of sampling, the steady-state heat currents exhibit turnovers as a function of the bath reorganization energy, with sharper turnovers in the classical case than in the quantum case and different temperature dependencies of the turnover maxima. As the temperature gap between the hot and cold baths increases, we observe an increasing difference in the steady-state heat currents obtained with the classical and quantum bath sampling. In general, as the bath temperatures are increased, the differences between the results of the classical and quantum bath sampling decrease but remain non-negligible at the high bath temperatures. The differences are attributed to the more pronounced temperature dependence of the classical distribution compared to the quantum one. Moreover, we find that the steady-state fluctuation theorem only holds for this model in the Markovian regime when quantum bath sampling is used. Altogether, our results highlight the importance of quantum bath sampling in quantum-classical dynamics simulations of quantum heat transport.

Electronic dephasing of polyatomic molecules interacting with mixed quantum-classical media.

This paper offers an expedient, efficient, and unique treatment of multimode quantum subsystems (polyatomic molecules) interacting with a classical environment in which the time evolution of the coupling term is governed by the algebraic rules of statistical mechanics in mixed quantum-classical systems developed by Kapral and Nielsen [S. Nielsen, R. Kapral, and G. Ciccotti, J. Chem. Phys., 2001, 115, 5805]. This unique time evolution of the coupling term is neither quantal nor classical but rather something different that relies heavily on Wigner transform, thereby leading to non-Newtonian mechanics. As such, an argument is presented that the approach provided herein for treating polyatomic molecular systems in a mixed quantum-classical environment is new and different as opposed to the many other schemes of semiclassical dynamics that are normally employed to study such systems. The merits of expediency and efficiency of the herein mixed quantum-classical dynamics calculations emanate from avoiding using integrals for time evolutions, and, instead, employing matrix mechanics whereby LU decomposition and singular value decomposition (SVD) numerical techniques are utilized for diagonalization. An electronic 2-level subsystem interacting with a classical bath through the spin-boson model to render accurate pure electronic dephasing in multimode molecular systems by eliminating the unphysical asymmetry in the line shape of the zero-phonon line (ZPL) exhibited by other models is exploited. This work has a superior advantage over the single-mode spin-boson model, published previously, whereby a multitude of types of vibrational modes (slow, fast, or both) of the quantum subsystem may readily be handled using different spectral densities. The spin-boson model used here is a composite system made up of a quantum subsystem, i.e., a subsystem bilinearly coupled to a multidimensional harmonic oscillator (representing the intermediate quantum vibrational modes between the electronic subsystem and the bath), interacting with a classical bath, where the coupling term is governed by the mixed quantum-classical Liouville equation. A multidimensional coherent-state approach is employed to deal with the time evolution of the quantum subsystem. A closed-form expression of linear and nonlinear optical electronic transition dipole moment time correlation functions in mixed quantum-classical dissipative media is derived. Pure electronic dephasing is probed using the aforementioned approach. Linear absorption spectra and 4-wave mixing signals (e.g., photon echo and pump-probe) are calculated showing a reasonable thermal broadening, temporal decay, and accurate pure dephasing.

Bose Gas in Classical Environment at Low Temperatures

The properties of a dilute Bose gas with the non-Gaussian quenched disorder are analyzed. Being more specific, we have considered a system of bosons immersed in the classical bath consisting of the non-interacting particles with infinite mass. Making use of perturbation theory up to the second order, we have studied the impact of environment on the ground-state thermodynamic and superfluid characteristics of the Bose component.

Revisiting the Past: Material Negotiations between the Classic Maya and an Entombed Sweat Bath at Xultun, Guatemala

Large material accumulations from single events found in the archaeological record are frequently defined as evidence of ritual. They are interpreted as generalized deposit categories that imply rather than infer human motivations. While useful in the initial collection of data, these categories can, over time, become interpretations in and of themselves. The emic motivations behind the formation process of ‘ritual deposits’ ought to be considered using a relational ontology as an approach to understanding how past populations interacted with non-human actors, such as structures and natural features on the landscape. The present study evaluates the assembly and possible function of a dense deposit of artifacts recovered from a Classic period sweat bath at Xultun, Guatemala. Analyses of the various artifact types and human remains in the deposit in relation to what is known of the social history of the sweat bath itself illustrate ontological relationships among offered materials as well as between the offering and the personified place in which it was recovered. We observe that with a better understanding of place, it is possible to evaluate the ritual logic in Classic Maya material negotiations.

Hammam-i-Bukhari (Turkish bath): A promising regimenal mode of Unani treatment.

Hammam-i-Bukhari (Turkish bath) is one of the important regimens used for the prevention and cure of several bodily ailments in Unani system of medicine. This regimen is usually practiced in the Arab world. The classical Turkish bath is built in the form of cavernous structure with beautiful classy mosaics and fountains. This regimenal therapy advocates physical, psychological and cosmetic health by integral cleansing which has different corporal effects appearing in biological along with molecular level. This therapy reduces the viscosity of the khilt (humour), eliminates the khilt-i-radi (morbid matters) and also diverts the morbid matters to the surface of the body from deep seated organs. Unani physicians, sometimes advise to patients for massage and several other regimens with different medicated substances before hammam to enhance the physiological activity from where hammam eliminates by its unique actions which helps in establishing a state of humoural equilibrium thus promoting health. Due to its efficacy and necessity; this therapeutic module is gaining popularity and assuming greater prominence among patients who are referred by physicians. The present review will dwell at length various modalities of hammam with its beneficial effects so that wholesome wellness could be attained by practical indulgence.

Computational modeling of charge hopping dynamics along a disordered one-dimensional wire with energy gradients in quantum environments.

This computational study investigates the effects of energy gradients on charge hopping dynamics along a one-dimensional chain of discrete sites coupled to quantum bath, which is modeled at the level of Pauli master equation (PME). This study also assesses the performance of different approximations for the hopping rates. Three different methods for solving the PME, a fourth order Runge-Kutta method, numerical diagonalization of the rate matrix followed by analytic propagation, and kinetic Monte Carlo simulation method, are tested and confirmed to produce virtually identical values of time dependent mean square displacement, diffusion constant, and mobility. Five different rate expressions, exact numerical evaluation of Fermi's Golden Rule (FGR) rate, stationary phase interpolation (SPI) approximation, semiclassical approximation, classical Marcus rate, and Miller-Abrahams rate, are tested to help understand the effects of approximations in representing quantum environments in the presence of energy gradients. The results based on direct numerical evaluation of FGR rate exhibit transition from diffusive to non-diffusive behavior with the increase in the gradient and show that the charge transport in the quantum bath is more sensitive to the magnitude of the gradient and the disorder than in the classical bath. Among all the four approximations for the hopping rates, the SPI approximation is confirmed to work best overall. A comparison of two different methods to calculate the mobility identifies drift motion of the population distribution as the major source of non-diffusive behavior and provides more reliable information on the contribution of quantum bath.

Not your classic bath: adopting and adapting Roman bathing habits in NW Gaul

Roman-style bathhouses are often used as markers to study processes of ‘Romanisation’, or, more generally, the spread of a Roman way of life throughout newly conquered regions. The building type, with its characteristic hypocaust system and pools, was a foreign element in regions unacquainted with communal bathing. However, to assume that these buildings were introduced and spread as a ‘package’, with the standard sequence of rooms and accompanying technology, would be oversimplifying a complex phenomenon of acceptance, rejection and adaptation. Since Roman baths are too often perceived as a mainly urban phenomenon, regions on the fringes of the empire with low levels of urbanisation, including the northern provinces, have been excluded from most seminal works.1 The present paper aims to examine a corpus of baths in NW Gaul from between the 1st and early 4th c. (i.e., the period between the first villa constructions and their abandonment following Germanic invasions) in order to challenge idées fixes2 that their plans were rigid and standardised and that most were in urban settings.

Efficient quantum transport in a multi-site system combining classical noise and quantum baths

We study the population dynamics and quantum transport efficiency of a multi-site dissipative system driven by a random telegraph noise (RTN) by using a variational polaron master equation for both linear chain and ring configurations. By using two different environment descriptions—RTN only and a thermal bath+RTN—we show that the presence of the classical noise has a non-trivial role on quantum transport. We observe that there exist large areas of parameter space where the combined bath+RTN influence is clearly beneficial for populating the target state of the transport, and for average trapping time and transport efficiency when accounting for the presence of the reaction center via the use of the sink. This result holds for both of the considered intra-site coupling configurations including a chain and ring. In general, our formalism and achieved results provide a platform for engineering and characterizing efficient quantum transport in multi-site systems both for realistic environments and engineered systems.

From βαλανεῖα to thermae: unveiling the transition from Greek to Roman architectural models of baths by technological and provenance archaeometric studies on bricks and tiles

So far unexplored, the introduction and the spread of the Roman thermal buildings in the prima provincia (Sicily) are widely debated in the current archeological studies. Mainly due to the lack of systematic excavations and intensively technological studies, the assessment of thermae in the Hellenistic-Roman Sicily has been thus far interpreted as a new social and architectural experience. However, a more careful archeological investigation would suggest a gradual transformation of the architectural landscape from the purely Greek bath tradition to the canonical thermae types. The aim of this paper is therefore to study the classical hot bath culture and, in particular, the transition from Greek to Roman architectural models (from βαλανεῖα to thermae) by applying an archaeometric approach on brick and tile samples from three Sicilian archaeological sites - Solunto, Taormina, Tindari - recently proved to be among the first towns in Sicily in which Roman thermae were established in the Early Empire. Petrographic, mineralogical (XRD), micromorphological (SEM) and geochemical (XRF) analyses has been performed on a selection of bath building remains (comprising suspensurae, tiles, bricks) to explore technology and production issues. The obtained results allowed to identify local productions and to distinguish them from imports, redrawing some aspects of the historical, economic, social and technological construction context of Roman Sicily.