arXiv subjects

M. Tahir Naseem

Publications and source records attributed to M. Tahir Naseem.

At least 19 recordsLinked to original sources

arXiv2026

Anti-Zeno boost in an autonomous quantized-piston thermal machine

Anti-Zeno enhancement of quantum heat machines has been established for working fluids driven by an external classical field, but whether the same quantum advantage survives when a quantized piston replaces the classical drive has remained open. Here we study an autonomous thermal machine in which a two-level working fluid is coupled to a quantized harmonic piston and to two spectrally separated reservoirs, without external modulation. We derive a finite-time master equation for the resulting carrier and sideband channels, whose rates interpolate between the Zeno, anti-Zeno, and Markovian regimes as the coupling time is varied. For an initially coherent piston, the machine charges the piston and generates more ergotropy than the Markovian reference in the anti-Zeno window. Reversing the same retained channels turns the device into a finite-resource refrigerator with enhanced cooling. The anti-Zeno effect therefore increases the rate of operation while leaving the underlying carrier and sideband energy ratios unchanged. These channel ratios remain consistent with the usual Carnot bounds over the operating regimes considered here. Our results establish finite-time reservoir sampling as a mechanism for enhancing autonomous thermal-machine operation with a quantized piston, without external modulation.

quant-ph↗

arXiv2026

Engineering a Quantum Thermal Diode with Floquet Driving

Controlling heat flow in small quantum systems is a central goal of quantum thermodynamics and nanoscale transport. A key challenge is to achieve strong thermal rectification without suppressing the transmitted heat current, a tradeoff that often arises in static diode configurations. We establish a Floquet-control mechanism in a minimal quantum thermal diode formed by two longitudinally modulated Ising-coupled qubits, each coupled to an independent thermal reservoir. From a microscopic system--bath model, we derive a Floquet--LGKS master equation that resolves the drive-assisted transition channels. The resonant undriven device with left--right symmetric bath couplings serves as the reciprocal benchmark, while static detuning provides a rectifying reference with reduced heat current. Single-side driving breaks this reciprocal structure by creating a Floquet-dressed contact opposite a purely thermal contact. For this configuration, we obtain a compact steady-state current formula and an exact blocking condition for suppressing one bias direction while retaining finite transport in the opposite direction. In the weak sinusoidal-drive regime, rectification begins quadratically in the modulation amplitude. Dual-side driving adds a Floquet pumping contribution to the interaction-mediated current, so complete blocking requires cancellation of both contributions. These results establish contact-selective Floquet dressing as a design principle for controllable heat-flow asymmetry in minimal quantum thermal devices.

quant-ph↗

arXiv2026

Reservoir-Engineered Mechanical Cat States with a Driven Qubit

Macroscopic quantum superpositions, such as mechanical Schrödinger cat states, are central to emerging quantum technologies in sensing and bosonic error-correcting codes. We propose a scheme to generate such states by coupling a nanomechanical resonator to a coherently driven two-level system via both transverse and longitudinal interactions. Driving the qubit at twice the oscillator frequency activates resonant two-phonon exchange processes, enabling coherent conversion of drive energy into phonon pairs and their dissipative stabilization. Starting from the full time-dependent Hamiltonian, we derive an effective master equation for the mechanical mode by perturbative elimination of the lossy qubit. The reduced dynamics feature engineered two-phonon loss and a coherent squeezing term, which together drive the resonator into a deterministic Schrödinger-cat state. Our approach requires only a single driven qubit and no auxiliary cavity, offering a scalable and experimentally accessible route to macroscopic quantum superpositions in circuit-QED and related platforms.

quant-ph↗

arXiv2025

Quantum thermal rectification via state-dependent two-photon dissipation

Controlling heat flow at the quantum level is essential for the development of next-generation thermal devices. We investigate thermal rectification in a quantum harmonic oscillator coupled to two thermal baths via both single-photon (linear) and two-photon (nonlinear) exchange processes. At low temperatures, rectification arises from a state-dependent suppression of two-photon emission: when the cold bath dominates, it drives the oscillator into low-occupancy states, inhibiting emission and creating a thermal bottleneck. At higher temperatures, rectification is governed by the asymmetric scaling of higher-order moments associated with two-photon absorption and emission. We systematically explore various bath coupling configurations and identify the conditions under which nonlinear dissipation leads to directional heat flow. Furthermore, we propose an implementation scheme based on coupling an auxiliary two-level system to the oscillator, enabling effective two-photon dissipation. These results contribute to the understanding of quantum heat transport in the presence of nonlinear dissipation and may support future efforts in nanoscale thermal rectification design.

quant-ph↗

arXiv2025

Optimal strategies for transient and equilibrium quantum thermometry using Gaussian and non-Gaussian probes

We study temperature estimation using quantum probes, including single-mode initial states and two-mode states generated via stimulated parametric down-conversion in a nonlinear crystal at finite temperature. We explore both transient and equilibrium regimes and compare the performance of Gaussian and non-Gaussian probe states for temperature estimation. In the non-equilibrium regime, we show that single-mode non-Gaussian probe states - such as Fock, odd cat, and Gottesman-Kitaev-Preskill states - can significantly enhance the speed of estimation, particularly at short interaction times. In the two-mode setting, entangled states such as the two-mode squeezed vacuum, NOON state, and entangled cat state can enable access to temperature information at earlier times. In the equilibrium regime, we analyze temperature estimation using two-mode squeezed thermal states, which outperform single-mode strategies. We evaluate practical measurement strategies and find that energy-based observables yield optimal precision, population difference observables provide near-optimal precision, while quadrature-based measurements are suboptimal. The precision gain arises from squeezing, which suppresses fluctuations in the population difference.

quant-ph↗

arXiv2024

Mixing thermal coherent states for precision and range enhancement in quantum thermometry

The unavoidable interaction between thermal environments and quantum systems typically leads to the degradation of quantum coherence, which can be fought against by reservoir engineering. We propose the realization of a special mixture of thermal coherent states by coupling a thermal bath with a two-level system that is longitudinally coupled to a resonator. We find that the state of the resonator is a special mixture of two oppositely displaced thermal coherent states, whereas the two-level system remains thermal. This observation is verified by evaluating the second-order correlation coefficient for the resonator state. Moreover, we reveal the potential benefits of employing the mixture of thermal coherent states of the resonator in quantum thermometry. In this context, the resonator functions as a probe to measure the unknown temperature of a bath mediated by a two-level system, strategically bridging the connection between the two. Our results show that the use of an ancillary-assisted probe may enhance the precision and broaden the applicable temperature range.

quant-ph↗

arXiv2024

Quantum thermometry with an optomechanical system

We present a quantum thermometry method utilizing an optomechanical system composed of an optical field coupled to a mechanical resonator for measuring the unknown temperature of a thermal bath. To achieve this, we connect a thermal bath to the mechanical resonator and perform measurements on the optical field, serving as a probe thermometer. Using the open quantum systems approach, we numerically calculate the quantum Fisher information for the probe. We find that, in specific parameter regimes, the system exhibits clusters of densely packed energy eigenstates interspaced with substantial energy gaps. This clustering of energy levels results in quasi-degeneracy within these energy eigenstate groups and hence widens the operational range of temperature estimation. Moreover, thermal sensitivity, especially at low temperatures, can be further boosted by appropriately tuning the essential system parameters.

quant-ph↗

arXiv2023

Signature of topology via heat transfer analysis in the Su-Schrieffer-Heeger (SSH) model

In this work, we explore the potential of thermodynamics as a tool for identifying the topological phase transition. Specifically, we focus on a one-dimensional Su-Schrieffer-Heeger (SSH) chain sandwiched between two fermionic baths. To investigate distinctive thermodynamic signatures associated with the topological phase, we employ heat flow analysis. Our results, derived using a global master equation, unveil a significant suppression of heat flow as we transition from the trivial to the topological phase. This decline in heat flow can be attributed to the reduction in transmission coefficients of non-zero energy modes within the topological phase. It may serve as an indicator of a phase transition. Furthermore, we investigate the heat flow asymmetry to search for phase transition indicators. Interestingly, no asymmetry is observed when employing fermionic baths. However, upon substituting fermionic baths with bosonic ones, we report a non-zero heat flow asymmetry. For the SSH model with a few fermionic sites, this asymmetry is more pronounced in the topological phase compared to the trivial phase. Therefore, the observed behavior of the heat diode provides an additional means of distinguishing between the topological and trivial phases. Finally, we delve into the contributions from both bulk and edge effects in heat flow and rectification to explore the impact of small system sizes on our findings.

cond-mat.stat-mech↗

arXiv2023

Low-temperature quantum thermometry boosted by coherence generation

The precise measurement of low temperatures is significant for both the fundamental understanding of physical processes and technological applications. In this work, we present a method for low-temperature measurement that improves thermal range and sensitivity by generating quantum coherence in a thermometer probe. Typically, in temperature measurements, the probes thermalize with the sample being measured. However, we use a two-level quantum system, or qubit, as our probe and prevent direct probe access to the sample by introducing a set of ancilla qubits as an interface. We describe the open system dynamics of the probe using a global master equation and demonstrate that while the ancilla-probe system thermalizes with the sample, the probe \textit{per se} evolves into a nonthermal steady state due to nonlocal dissipation channels. The populations and coherences of this steady state depend on the sample temperature, allowing for precise and wide-range low-temperature estimation. We characterize the thermometric performance of the method using quantum Fisher information and show that the quantum Fisher information can exhibit multiple and higher peaks at different low temperatures with increasing quantum coherence and the number of ancilla qubits. Our analysis reveals that the proposed approach, using a nonthermal qubit thermometer probe with temperature-dependent quantum coherence generated by a multiple qubit interface between a thermal sample and the probe qubit, can enhance the sensitivity of temperature estimation and broaden the measurable low-temperature range.

quant-ph↗

arXiv2022

Enantiomer detection via Quantum Otto cycle

Enantiomers are chiral molecules that exist in right-handed and left-handed conformations. Optical techniques of enantiomers detection are widely employed to discriminate between left- and right-handed molecules. However, identical spectra of enantiomers make enantiomer detection a very challenging task. Here, we investigate the possibility of exploiting thermodynamic processes for enantiomer detection. In particular, we employ a quantum Otto cycle, in which a chiral molecule described by a three-level system with cyclic optical transitions is considered a working medium. Each energy transition of the three-level system is coupled with an external laser drive. We find that the left-handed molecule works as a heat engine, while the right-handed molecule works as a thermal accelerator where the overall phase of the drives is considered as the cycle's control parameter. In addition, both left- and right-handed molecules work as heat engines by considering laser drives' detuning as the control parameter. However, the molecules can still be distinguished because both cases' extracted work and efficiency are quantitatively very different. Accordingly, left and right-handed molecules can be distinguished by evaluating the work distribution in the Otto cycle.

quant-ph↗

arXiv2022

Engineering entanglement between resonators by hot environment

Autonomous quantum thermal machines do not require an external coherent drive or work input to perform the desired tasks, which makes them a promising candidate for thermal management in quantum systems. Here, we propose an autonomous quantum thermal machine in which two uncoupled macroscopic mechanical resonators or microwave resonators achieve considerable entanglement via a hot thermal bath. This becomes possible by coupling the resonators to a common two-level system or third harmonic oscillator and driving it by the hot incoherent thermal bath. The critical step to make the entanglement involves suitable engineering of the hot bath, realized by bath spectrum filtering. Our results suggest that the bath spectrum filtering can be an alternative to typical non-autonomous reservoir engineering schemes to create exotic quantum states.

quant-ph↗

arXiv2022

Antibunching via cooling by heating

We investigate statistics of the photon (phonon) field undergoing linear and nonlinear damping processes. An effective two-photon (phonon) nonlinear "cooling by heating" process is realized from linear damping by spectral filtering of the heat baths present in the system. This cooling process driven by incoherent quantum thermal noise can create quantum states of the photon field. In fact, for high temperatures of the spectrally filtered heat baths, sub-Poissonian statistics with strong antibunching in the photon (phonon) field are reported. This notion of the emergence and control of quantumness by incoherent thermal quantum noise is applied to a quantum system comprising of a two-level system and a harmonic oscillator or analogous optomechanical setting. Our analysis may provide a promising direction for the preparation and protection of quantum features via nonlinear damping that can be controlled with incoherent thermal quantum noise.

quant-ph↗

arXiv2021

Heat rectification by two qubits coupled with Dzyaloshinskii-Moriya interaction

We investigate heat rectification in a two-qubit system coupled via the Dzyaloshinskii-Moriya (DM) interaction. We derive analytical expressions for heat currents and thermal rectification and provide possible physical mechanisms behind the observed results. We show that the anisotropy of DM interaction in itself is insufficient for heat rectification, and some other form of asymmetry is needed. We employ off-resonant qubits as the source of this asymmetry. We find the regime of parameters for higher rectification factors by examining the analytical expressions of rectification obtained from a global master equation solution. In addition, it is shown that the direction and quality of rectification can be controlled via various system parameters. Furthermore, we compare the influence of different orientations of the DM field anisotropy on the performance of heat rectification. Finally, we investigate the possible interplay between quantum correlations and the performance of the quantum thermal rectifier. We find that asymmetry in the coherences is a fundamental resource for the performance of the quantum thermal rectifier.

cond-mat.stat-mech↗

arXiv2021

Ground-state cooling of mechanical resonators by quantum reservoir engineering

We propose a scheme to cool down a mechanical resonator to its quantum ground-state, which is interacting with a working fluid via an optomechanical-like coupling. As opposed to standard laser cooling schemes where coherence renders the motion of a resonator to its ground-state, we consider an incoherent thermal source to achieve the same aim. We show that simultaneous cooling of two degenerate or near-degenerate mechanical resonators is possible, which is otherwise a challenging goal to achieve. The generalization of this method to the simultaneous cooling of multiple resonators is straightforward. Spectral filtering of the coupling between the cooling agent and the baths is a key to realize cooling in our scheme. The underlying physical mechanism of cooling is explained by investigating a direct connection between the laser sideband cooling and cooling by heating in a standard optomechanical setting. Our advantageous scheme of cooling enabled by quantum reservoir engineering can be realized in various setups, employing parametric coupling of a cooling agent with the target systems. We also discuss using non-thermal baths to simulate ultra-high temperature thermal baths for cooling.

quant-ph↗

arXiv2020

Tunable multiwindow magnomechanically induced transparency, Fano resonances, and slow-to-fast light conversion

We investigate the absorption and transmission properties of a weak probe field under the influence of a strong control field in a hybrid cavity magnomechanical system in the microwave regime. This hybrid system consists of two ferromagnetic material yttrium iron garnet (YIG) spheres strongly coupled to a single cavity mode. In addition to two magnon-induced transparency (MIT) that arise due to strong photon-magnon interactions, we observe a magnomechanically induced transparency (MMIT) due to the presence of nonlinear phonon-magnon interaction. In addition, we discuss the emergence and tunability of the multiple Fano resonances in our system. We find that due to strong photon-magnon coupling the group delay of the probe field can be enhanced significantly. The subluminal or superluminal propagation depends on the frequency of the magnons, which can be easily tuned by an external bias magnetic field. Besides, the group delay of the transmitted field can also be controlled with the control field power.

quant-ph↗

arXiv2020

Minimal quantum heat manager boosted by bath spectral filtering

We reveal the potentially important role of a general mechanism that has hitherto not been invoked in quantum heat management schemes, namely, spectral filtering of the coupling between the heat baths in the setup and the quantum system that controls the heat flow. Such filtering is enabled by interfaces between the system and the baths by means of harmonic-oscillator modes whose resonant frequencies and coupling strengths are used as control parameters of the system-bath coupling spectra. We show that this uniquely quantum-electrodynamic mechanism, here dubbed bath spectral filtering, boosts the performance of a minimal quantum heat manager comprised of two interacting qubits or an analogous optomechanical system, allowing this device to attain either perfect heat diode action or strongly enhanced heat transistor action.

quant-ph↗

arXiv2020

Two-body quantum absorption refrigerators with optomechanical-like interactions

Quantum absorption refrigerator (QAR) autonomously extracts heat from a cold bath and dumps into a hot bath by exploiting the input heat from a higher temperature reservoir. QARs typically require three-body interactions. We propose and examine a two-body QAR model based upon optomechanical-like coupling in the working medium composed of either two two-level systems or two harmonic oscillators or one two-level atom and a harmonic oscillator. In the ideal case without internal dissipation, within the experimentally realizable parameters, our model can attain the coefficient of performance that is arbitrarily close to the Carnot bound. We study the efficiency at maximum power, a bound for practical purposes, and show that by using suitable reservoir engineering and exploiting the nonlinear optomechanial-like coupling, one can achieve efficiency at maximum power close to the Carnot bound, though the power gradually approaches to zero as the efficiency approaches the Carnot bound. Moreover, we discuss the impact of non-classical correlations and the size of Hilbert space on the cooling power. Finally, we consider a more realistic version of our model in which we consider heat leaks that makes QAR non-ideal and prevent it to achieve the Carnot efficiency.

quant-ph↗

arXiv2019

Quantum heat engine with a quadratically coupled optomechanical system

We propose a quantum heat engine based on a quadratically coupled optomechanical system. The optical component of the system is driven periodically with an incoherent thermal drive, which induces periodic oscillations in the mechanical component. Under the action of the quadratic optomechanical interaction, the mechanical mode evolves from an initial thermal state to a thermal-squeezed steady state, as verified by calculating the Wigner functions. The dynamics of the system is identified as an effective four-stroke Otto cycle. We investigated the performance of the engine by evaluating the dissipated power, the maximum power under a load, and the maximum extractable work. It is found that the engine operating with quadratic optomechanics is more powerful than the one operating with linear optomechanics. The effect is explained by the presence of squeezing in the quantum state of the mechanical mode.

quant-ph↗