9 research outputs found
Hamiltonian learning with real-space impurity tomography in topological moire superconductors
Extracting Hamiltonian parameters from available experimental data is a
challenge in quantum materials. In particular, real-space spectroscopy methods
such as scanning tunneling spectroscopy allow probing electronic states with
atomic resolution, yet even in those instances extracting effective Hamiltonian
is an open challenge. Here we show that impurity states in modulated systems
provide a promising approach to extracting non-trivial Hamiltonian parameters
of a quantum material. We show that by combining the real-space spectroscopy of
different impurity locations in a moire topological superconductor, modulations
of exchange and superconducting parameters can be inferred via machine
learning. We demonstrate our strategy with a physically-inspired harmonic
expansion combined with a fully-connected neural network that we benchmark
against a conventional convolutional architecture. We show that while both
approaches allow extracting exchange modulations, only the former approach
allows inferring the features of the superconducting order. Our results
demonstrate the potential of machine learning methods to extract Hamiltonian
parameters by real-space impurity spectroscopy as local probes of a topological
state.Comment: 11 pages, 8 figure
Adversarial Hamiltonian learning of quantum dots in a minimal Kitaev chain
Determining Hamiltonian parameters from noisy experimental measurements is a
key task for the control of experimental quantum systems. An experimental
platform that recently emerged, and where knowledge of Hamiltonian parameters
is crucial to fine-tune the system, is that of quantum dot-based Kitaev chains.
In this work, we demonstrate an adversarial machine learning algorithm to
determine the parameters of a quantum dot-based Kitaev chain. We train a
convolutional conditional generative adversarial neural network (Conv-cGAN)
with simulated differential conductance data and use the model to predict the
parameters at which Majorana bound states are predicted to appear. In
particular, the Conv-cGAN model facilitates a rapid, numerically efficient
exploration of the phase diagram describing the transition between elastic
co-tunneling and crossed Andreev reflection regimes. We verify the theoretical
predictions of the model by applying it to experimentally measured conductance
obtained from a minimal Kitaev chain consisting of two spin-polarized quantum
dots coupled by a superconductor-semiconductor hybrid. Our model accurately
predicts, with an average success probability of \%, whether the
measurement was taken in the elastic co-tunneling or crossed Andreev
reflection-dominated regime. Our work constitutes a stepping stone towards
fast, reliable parameter prediction for tuning quantum-dot systems into
distinct Hamiltonian regimes. Ultimately, our results yield a strategy to
support Kitaev chain tuning that is scalable to longer chains
Hamiltonian inference from dynamical excitations in confined quantum magnets
Quantum-disordered models provide a versatile platform to explore the
emergence of quantum excitations in many-body systems. The engineering of spin
models at the atomic scale with scanning tunneling microscopy and the local
imaging of excitations with electrically driven spin resonance has risen as a
powerful strategy to image spin excitations in finite quantum spin systems.
Here, focusing on lattices as realized by Ti in MgO, we show that
dynamical spin excitations provide a robust strategy to infer the nature of the
underlying Hamiltonian. We show that finite-size interference of the dynamical
many-body spin excitations of a generalized long-range Heisenberg model allows
the underlying spin couplings to be inferred. We show that the spatial
distribution of local spin excitations in Ti islands and ladders directly
correlates with the underlying ground state in the thermodynamic limit. Using a
supervised learning algorithm, we demonstrate that the different parameters of
the Hamiltonian can be extracted by providing the spatially and
frequency-dependent local excitations that can be directly measured by
electrically driven spin resonance with scanning tunneling microscopy. Our
results put forward local dynamical excitations in confined quantum spin models
as versatile witnesses of the underlying ground state, providing an
experimentally robust strategy for Hamiltonian inference in complex real spin
models.Comment: 11 pages, 10 figure
Modern applications of machine learning in quantum sciences
In these Lecture Notes, we provide a comprehensive introduction to the most
recent advances in the application of machine learning methods in quantum
sciences. We cover the use of deep learning and kernel methods in supervised,
unsupervised, and reinforcement learning algorithms for phase classification,
representation of many-body quantum states, quantum feedback control, and
quantum circuits optimization. Moreover, we introduce and discuss more
specialized topics such as differentiable programming, generative models,
statistical approach to machine learning, and quantum machine learning.Comment: 268 pages, 87 figures. Comments and feedback are very welcome.
Figures and tex files are available at
https://github.com/Shmoo137/Lecture-Note
Neural network enhanced hybrid quantum many-body dynamical distributions
Computing dynamical distributions in quantum many-body systems represents one of the paradigmatic open problems in theoretical condensed matter physics. Despite the existence of different techniques both in real-time and frequency space, computational limitations often dramatically constrain the physical regimes in which quantum many-body dynamics can be efficiently solved. Here we show that the combination of machine-learning methods and complementary many-body tensor network techniques substantially decreases the computational cost of quantum many-body dynamics. We demonstrate that combining kernel polynomial techniques and real-time evolution, together with deep neural networks, allows to compute dynamical quantities faithfully. Focusing on many-body dynamical distributions, we show that this hybrid neural-network many-body algorithm, trained with single-particle data only, can efficiently extrapolate dynamics for many-body systems without prior knowledge. Importantly, this algorithm is shown to be substantially resilient to numerical noise, a feature of major importance when using this algorithm together with noisy many-body methods. Ultimately, our results provide a starting point towards neural-network powered algorithms to support a variety of quantum many-body dynamical methods, that could potentially solve computationally expensive many-body systems in a more efficient manner.Peer reviewe
Designing quantum many-body matter with conditional generative adversarial networks
The computation of dynamical correlators of quantum many-body systems represents an open critical challenge in condensed matter physics. While powerful methodologies have risen in recent years, covering the full parameter space remains unfeasible for most many-body systems with a complex configuration space. Here we demonstrate that conditional generative adversarial networks (GANs) allow simulating the full parameter space of several many-body systems, accounting both for controlled parameters and for stochastic disorder effects. After training with a restricted set of noisy many-body calculations, the conditional GAN algorithm provides the whole dynamical excitation spectra for a Hamiltonian instantly and with an accuracy analogous to the exact calculation. We further demonstrate how the trained conditional GAN automatically provides a powerful method for Hamiltonian learning from its dynamical excitations, and how to flag nonphysical systems via outlier detection. Our methodology puts forward generative adversarial learning as a powerful technique to explore complex many-body phenomena, providing a starting point to design large-scale quantum many-body matter.Peer reviewe
Hamiltonian learning with real-space impurity tomography in topological moiré superconductors
Extracting Hamiltonian parameters from available experimental data is a challenge in quantum materials. In particular, real-space spectroscopy methods such as scanning tunneling spectroscopy allow probing electronic states with atomic resolution, yet even in those instances extracting the effective Hamiltonian is an open challenge. Here we show that impurity states in modulated systems provide a promising approach to extracting non-trivial Hamiltonian parameters of a quantum material. We show that by combining the real-space spectroscopy of different impurity locations in a moiré topological superconductor, modulations of exchange and superconducting parameters can be inferred via machine learning. We demonstrate our strategy with a physically-inspired harmonic expansion combined with a fully-connected neural network that we benchmark against a conventional convolutional architecture. We show that while both approaches allow extracting exchange modulations, only the former approach allows inferring the features of the superconducting order. Our results demonstrate the potential of machine learning methods to extract Hamiltonian parameters by real-space impurity spectroscopy as local probes of a topological state
Strain Control of Exciton–Phonon Coupling in Atomically Thin Semiconductors
Semiconducting
transition metal dichalcogenide (TMDC) monolayers
have exceptional physical properties. They show bright photoluminescence
due to their unique band structure and absorb more than 10% of the
light at their excitonic resonances despite their atomic thickness.
At room temperature, the width of the exciton transitions is governed
by the exciton–phonon interaction leading to strongly asymmetric
line shapes. TMDC monolayers are also extremely flexible, sustaining
mechanical strain of about 10% without breaking. The excitonic properties
strongly depend on strain. For example, exciton energies of TMDC monolayers
significantly redshift under uniaxial tensile strain. Here, we demonstrate
that the width and the asymmetric line shape of excitonic resonances
in TMDC monolayers can be controlled with applied strain. We measure
photoluminescence and absorption spectra of the A exciton in monolayer
MoSe<sub>2</sub>, WSe<sub>2</sub>, WS<sub>2</sub>, and MoS<sub>2</sub> under uniaxial tensile strain. We find that the A exciton substantially
narrows and becomes more symmetric for the selenium-based monolayer
materials, while no change is observed for atomically thin WS<sub>2</sub>. For MoS<sub>2</sub> monolayers, the line width increases.
These effects are due to a modified exciton–phonon coupling
at increasing strain levels because of changes in the electronic band
structure of the respective monolayer materials. This interpretation
based on steady-state experiments is corroborated by time-resolved
photoluminescence measurements. Our results demonstrate that moderate
strain values on the order of only 1% are already sufficient to globally
tune the exciton–phonon interaction in TMDC monolayers and
hold the promise for controlling the coupling on the nanoscale