arXiv subjects

Nathan M. Myers

Publications and source records attributed to Nathan M. Myers.

14 recordsLinked to original sources

arXiv2026

Bosonic Working Media in a Frustrated Rhombi Chain: Otto and Stirling Cycles from Flat Bands, Caging, and Flux Control

We demonstrate that flat-band engineering provides a direct route to control and optimize the thermodynamic performance of quantum heat engines. We consider noninteracting bosons on a rhombic chain lattice described by a Bose-Hubbard model in the noninteracting limit, where a magnetic flux serves as a tunable parameter that continuously reshapes the single-particle spectrum. By driving the system toward the fully frustrated Aharonov-Bohm caging regime, the band structure transitions from dispersive to completely flat, strongly modifying the thermal occupation of the modes. We show that this flux-induced spectral restructuring has clear and measurable thermodynamic consequences. In particular, the Otto cycle exhibits a significant enhancement of both work output and efficiency when operating near the caging regime. We identify the underlying mechanism as a pronounced suppression of heat released to the cold reservoir, rather than an increase in absorbed heat, revealing that flat-band formation is an effective strategy to increase work extraction. In contrast, the Stirling cycle is governed by entropy changes during isothermal, flux-driven processes, leading to greater work extraction over a broader parameter range but at lower efficiency. These results establish geometric frustration and Aharonov-Bohm caging as thermodynamic resources and show that spectral engineering via synthetic gauge fields offers a viable, experimentally accessible pathway to tailor the performance of bosonic quantum thermal machines.

cond-mat.quant-gas↗

arXiv2026

Quantum Flow algorithm: quantum simulations of chemical systems using reduced quantum resources and constant depth quantum circuits

We assess the performance of the Quantum Flow (QFlow) algorithm employing cost-effective solvers based on the unitary coupled-cluster ansatz with single and double excitations (QFlow-SD). The resulting energies are benchmarked against those obtained with an analogous QFlow formulation defined in the same active spaces but augmented by higher-rank excitations, including triples and quadruples (QFlow-SDTQ). Across all molecular systems considered, QFlow-SD exhibits close agreement with results from the canonical unitary coupled cluster with singles and doubles framework, while requiring substantially fewer qubits than the latter. For the water molecule in the cc-pVTZ basis, we further demonstrate the performance of a composite two-step downfolding strategy. In this approach, an initial coupled-cluster downfolding based on the double unitary coupled-cluster ansatz is followed by a QFlow treatment within the resulting target space, illustrating the effectiveness of combining classical downfolding with quantum flow optimization.

physics.chem-ph↗

arXiv2025

Exact and Efficient Stabilizer Simulation of Thermal-Relaxation Noise for Quantum Error Correction

Stabilizer-based simulation of quantum error-correcting codes typically relies on the Pauli-twirling approximation (PTA) to render non-Clifford noise classically tractable, but PTA can distort the behavior of physically relevant channels such as thermal relaxation. Physically accurate noise simulation is needed to train decoders and understand the noise suppression capabilities of quantum error correction codes. In this work, we develop an exact and stabilizer-compatible model of qubit thermal relaxation noise and show that the combined amplitude damping and dephasing channel admits a fully positive probability decomposition into Clifford operations and reset whenever $T_2 \leqslant T_1$. For $T_2 > T_1$, the resulting decomposition is negative, but allows a smaller sampling overhead versus independent channels. We further introduce an approximated error channel with reset that removes the negativity of the decomposition while achieving higher channel fidelity to the true thermal relaxation than PTA, and extend our construction to finite temperature relaxation. We apply the exact combined model to investigate large surface codes and bivariate bicycle codes on superconducting platforms with realistic thermal relaxation error. The differing logical performances across code states further indicate that noise-model-informed decoders will be essential for accurately capturing thermal-noise structure in future fault-tolerant architectures.

quant-ph↗

arXiv2025

Toward Quantum Analog Simulation of Many-Body Supersymmetry with Rydberg Atom Arrays

A topological quantum number, the Witten index, characterizes supersymmetric models by probing for zero energy modes and the possibility of supersymmetry breaking. We propose an averaging method to infer the Witten index in quantum analog simulators. Motivated by recent work on Rydberg atoms trapped in optical tweezer arrays, we consider a related supersymmetric XXZ spin model. We show how to infer the Witten index from open system averaging and numerically demonstrate its topological robustness in this model. Our Letter defines a route for quantum analog simulators to directly identify many-body topological physics.

quant-ph↗

arXiv2025

Coupled Cluster Downfolding Theory in Simulations of Chemical Systems on Quantum Hardware

The practical application of quantum technologies to chemical problems faces significant challenges, particularly in the treatment of realistic basis sets and the accurate inclusion of electron correlation effects. A direct approach to these problems is currently infeasible due to limitations in the number of logical qubits, their fidelity, and the shallow circuit depths supported by existing hardware; all of which hinder simulations at the required level of accuracy. A promising alternative is hybrid quantum-classical computing, where classical resources are used to construct effective Hamiltonians characterized by dimensions that conform to the constraints of current quantum devices. In this paper, we demonstrate the performance of a hybrid approach: coupled-cluster downfolded Hamiltonians are first evaluated in reduced-dimensionality active spaces, and the corresponding ground-state energies are subsequently computed using quantum algorithms. Our comprehensive analysis explores the achievable accuracy in recovering correlation energies when hundreds of orbitals are downfolded into a problem size tractable by today's quantum hardware. We argue that such flexible hybrid algorithms, where problem size can be tailored to available quantum resources, can serve as a bridge between noisy intermediate-scale quantum (NISQ) devices and future fault-tolerant quantum computers, marking a step toward the early realization of quantum advantage in chemistry.

quant-ph↗

arXiv2025

Noise-resilient and resource-efficient hybrid algorithm for robust quantum gap estimation

We present a hybrid quantum algorithm for estimating gaps in many-body energy spectra, supported by an analytic proof of its inherent resilience to state preparation and measurement errors, as well as mid-circuit multi-qubit depolarizing noise. Our analysis extends to a broader class of Markovian noise, employing error mitigation strategies that optimize the utilization of quantum resources. By integrating trial-state optimization and classical signal processing into the algorithm, we amplify the signal peak corresponding to the exact target gap beyond the error threshold, thereby significantly reducing gap estimate errors. The algorithm's robustness is demonstrated through noisy simulations on the Qiskit Aer simulator and demonstrations on IBM Quantum processors. These results underscore the potential to enable accurate quantum simulations on near-term noisy quantum devices without resource-intensive error correction.

quant-ph↗

arXiv2025

Unifying Collisional Models and the Monte Carlo Metropolis Method: Algorithms for Dynamics of Open Quantum Systems

Classical systems placed in contact with a thermal bath will inevitably equilibrate to a thermal state at the bath temperature. The same is not generally true for open quantum systems, which place additional conditions on the structure of the bath and system-bath interaction if thermalization is to occur. Collisional models, or repeated interaction schemes, are a category of microscopic open quantum system models that have seen growing use in studying quantum thermalization, in which the bath is modeled as a large ensemble of identical ancilla systems that sequentially interact with the system. We demonstrate that, when each bath ancilla is prepared in a thermal state with a discrete spectrum that matches the energy eigenstate transitions of the system, the system dynamics generated by the collisional model framework are identical to those generated under the Metropolis algorithm. This equivalence holds not just in the steady state regime, but also in the transient regime. As the Metropolis scheme does not require explicitly modeling the system-bath interaction, this allows it to be used as a computationally efficient alternative for simulating collisional model dynamics.

quant-ph↗

arXiv2023

Quantum simulation costs for Suzuki-Trotter decomposition of quantum many-body lattice models

Quantum computers offer the potential to efficiently simulate the dynamics of quantum systems, a task whose difficulty scales exponentially with system size on classical devices. To assess the potential for near-term quantum computers to simulate many-body systems we develop a formalism to straightforwardly compute bounds on the number of Trotter steps needed to accurately simulate the time evolution of fermionic lattice models based on the first-order commutator scaling. We apply this formalism to two closely related many-body models prominent in condensed matter physics, the Hubbard and t-J models. We find that, while a naive comparison of the Trotter depth first seems to favor the Hubbard model, careful consideration of the model parameters and the allowable error for accurate simulation leads to a substantial advantage in favor of the t-J model. These results and formalism set the stage for significant improvements in quantum simulation costs.

quant-ph↗

arXiv2023

Enhanced Efficiency at Maximum Power in a Fock-Darwin Model Quantum Dot Engine

We study the performance of an endoreversible magnetic Otto cycle with a working substance composed of a single quantum dot described using the well-known Fock-Darwin model. We find that tuning the intensity of the parabolic trap (geometrical confinement) impacts the proposed cycle's performance, quantified by the power, work, efficiency, and parameter region where the cycle operates as an engine. We demonstrate that a parameter region exists where the efficiency at maximum output power exceeds the Curzon-Ahlborn efficiency, the efficiency at maximum power achieved by a classical working substance.

cond-mat.stat-mech↗

arXiv2022

Quantum thermodynamic devices: from theoretical proposals to experimental reality

Thermodynamics originated in the need to understand novel technologies developed by the Industrial Revolution. However, over the centuries the description of engines, refrigerators, thermal accelerators, and heaters has become so abstract that a direct application of the universal statements to real-life devices is everything but straight forward. The recent, rapid development of quantum thermodynamics has taken a similar trajectory, and, e.g., "quantum engines" have become a widely studied concept in theoretical research. However, if the newly unveiled laws of nature are to be useful, we need to write the dictionary that allows us to translate abstract statements of theoretical quantum thermodynamics to physical platforms and working mediums of experimentally realistic scenarios. To assist in this endeavor, this review is dedicated to providing an overview over the proposed and realized quantum thermodynamic devices, and to highlight the commonalities and differences of the various physical situations.

quant-ph↗

arXiv2021

Boosting engine performance with Bose-Einstein condensation

At low-temperatures a gas of bosons will undergo a phase transition into a quantum state of matter known as a Bose-Einstein condensate (BEC), in which a large fraction of the particles will occupy the ground state simultaneously. Here we explore the performance of an endoreversible Otto cycle operating with a harmonically confined Bose gas as the working medium. We analyze the engine operation in three regimes, with the working medium in the BEC phase, in the gas phase, and driven across the BEC transition during each cycle. We find that the unique properties of the BEC phase allow for enhanced engine performance, including increased power output and higher efficiency at maximum power.

cond-mat.stat-mech↗

arXiv2021

Quantum Otto engines at relativistic energies

Relativistic quantum systems exhibit unique features not present at lower energies, such as the existence of both particles and antiparticles, and restrictions placed on the system dynamics due to the light cone. In order to understand what impact these relativistic phenomena have on the performance of quantum thermal machines we analyze a quantum Otto engine with a working medium of a relativistic particle in an oscillator potential evolving under Dirac or Klein-Gordon dynamics. We examine both the low-temperature, non-relativistic and high-temperature, relativistic limits of the dynamics and find that the relativistic engine operates with higher work output, but an effectively reduced compression ratio, leading to significantly smaller efficiency than its non-relativistic counterpart. Using the framework of endoreversible thermodynamics we determine the efficiency at maximum power of the relativistic engine, and find it to be equivalent to the Curzon-Ahlborn efficiency.

cond-mat.stat-mech↗

arXiv2021

Thermodynamics of Statistical Anyons

In low-dimensional systems, indistinguishable particles can display statistics that interpolate between bosons and fermions. Signatures of these "anyons" have been detected in two-dimensional quasiparticle excitations of the fractional quantum Hall effect, however experimental access to these quasiparticles remains limited. As an alternative to these "topological anyons," we propose "statistical anyons" realized through a statistical mixture of particles with bosonic and fermionic symmetry. We show that the framework of statistical anyons is equivalent to the generalized exclusion statistics (GES) pioneered by Haldane, significantly broadening the range of systems to which GES apply. We develop the full thermodynamic characterizations of these statistical anyons, including both equilibrium and nonequilibrium behavior. To develop a complete picture, we compare the performance of quantum heat engines with working mediums of statistical anyons and traditional topological anyons, demonstrating the effects of the anyonic phase in both local equilibrium and fully nonequilibrium regimes. In addition, methods of optimizing engine performance through shortcuts to adiabaticity are investigated, using both linear response and fast forward techniques.

cond-mat.stat-mech↗

arXiv2019

Bosons Outperform Fermions -- The Thermodynamic Advantage of Symmetry

We examine a quantum Otto engine with a harmonic working medium consisting of two particles to explore the use of wave function symmetry as an accessible resource. It is shown that the bosonic system displays enhanced performance when compared to two independent single particle engines, while the fermionic system displays reduced performance. To this end, we explore the trade-off between efficiency and power output and the parameter regimes under which the system functions as engine, refrigerator, or heater. Remarkably, the bosonic system operates under a wider parameter space both when operating as an engine and as a refrigerator.

cond-mat.stat-mech↗