10 research outputs found
Quantum simulations of a qubit of space
In loop quantum gravity approach to Planck scale physics, quantum geometry is
represented by superposition of the so-called spin network states. In the
recent literature, a class of spin networks promising from the perspective of
quantum simulations of quantum gravitational systems has been studied. In this
case, the spin network states are represented by graphs with four-valent nodes,
and two dimensional intertwiner Hilbert spaces (qubits of space) attached to
them. In this article, construction of quantum circuits for a general
intertwiner qubit is presented. The obtained circuits are simulated on 5-qubit
(Yorktown) and 15-qubit (Melbourne) IBM superconducting quantum computers,
giving satisfactory fidelities. The circuits provide building blocks for
quantum simulations of complex spin networks in the future. Furthermore, a
class of maximally entangled states of spin networks is introduced. As an
example of application, attempts to determine transition amplitudes for a
monopole and a dipole spin networks with the use of superconducting quantum
processor are made.Comment: 17 pages. Matches the version published in PR
Quantum circuits for the Ising spin networks
Spin network states are a powerful tool for constructing the SU(2) gauge theories on a graph. In loop quantum gravity (LQG), they have yielded many promising predictions, although progress has been limited by the computational challenge of dealing with high-dimensional Hilbert spaces. To explore more general configurations, quantum computing methods can be applied by representing spin network states as quantum circuits. In this article, we introduce an improved method for constructing quantum circuits for 4-valent Ising spin networks, which utilizes a smaller number of qubits than previous approaches. This has practical implications for the implementation of quantum circuits. We also demonstrate the procedure with various examples, including the construction of a 10-node Ising spin network state. The key ingredient of the method is the variational transfer of partial states, which we illustrate through numerous examples. Our improved construction provides a promising avenue for further exploring the potential of quantum computing methods in quantum gravity research
The higher-order phase transition in toroidal CDT
We investigate the transition between the phases and observed in
four-dimensional Causal Dynamical Triangulations (CDT). We find that the
critical properties of CDT with toroidal spatial topology are the same as
earlier observed in spherical spatial topology where the transition was
found to be higher-order. This may have important consequences for the
existence of the continuum limit of CDT, describing the perspective UV limit of
quantum gravity, which potentially can be investigated in the toroidal model.Comment: 17 pages, 10 figure
Cloud Detection in Multispectral Satellite Images Using Support Vector Machines With Quantum Kernels
Support vector machines (SVMs) are a well-established classifier effectively
deployed in an array of pattern recognition and classification tasks. In this
work, we consider extending classic SVMs with quantum kernels and applying them
to satellite data analysis. The design and implementation of SVMs with quantum
kernels (hybrid SVMs) is presented. It consists of the Quantum Kernel
Estimation (QKE) procedure combined with a classic SVM training routine. The
pixel data are mapped to the Hilbert space using ZZ-feature maps acting on the
parameterized ansatz state. The parameters are optimized to maximize the kernel
target alignment. We approach the problem of cloud detection in satellite image
data, which is one of the pivotal steps in both on-the-ground and on-board
satellite image analysis processing chains. The experiments performed over the
benchmark Landsat-8 multispectral dataset revealed that the simulated hybrid
SVM successfully classifies satellite images with accuracy on par with classic
SVMs.Comment: Prepared for IGARSS 2023 Proceedings, 4 pages, 2 figure
Optimizing Kernel-Target Alignment for cloud detection in multispectral satellite images
The optimization of Kernel-Target Alignment (TA) has been recently proposed
as a way to reduce the number of hardware resources in quantum classifiers. It
allows to exchange highly expressive and costly circuits to moderate size, task
oriented ones. In this work we propose a simple toy model to study the
optimization landscape of the Kernel-Target Alignment. We find that for
underparameterized circuits the optimization landscape possess either many
local extrema or becomes flat with narrow global extremum. We find the
dependence of the width of the global extremum peak on the amount of data
introduced to the model. The experimental study was performed using
multispectral satellite data, and we targeted the cloud detection task, being
one of the most fundamental and important image analysis tasks in remote
sensing.Comment: Prepared for IGARSS 2023 Proceedings, 4 pages, 4 figure
Detecting Clouds in Multispectral Satellite Images Using Quantum-Kernel Support Vector Machines
Support vector machines (SVMs) are a well-established classifier effectively
deployed in an array of classification tasks. In this work, we consider
extending classical SVMs with quantum kernels and applying them to satellite
data analysis. The design and implementation of SVMs with quantum kernels
(hybrid SVMs) are presented. Here, the pixels are mapped to the Hilbert space
using a family of parameterized quantum feature maps (related to quantum
kernels). The parameters are optimized to maximize the kernel target alignment.
The quantum kernels have been selected such that they enabled analysis of
numerous relevant properties while being able to simulate them with classical
computers on a real-life large-scale dataset. Specifically, we approach the
problem of cloud detection in the multispectral satellite imagery, which is one
of the pivotal steps in both on-the-ground and on-board satellite image
analysis processing chains. The experiments performed over the benchmark
Landsat-8 multispectral dataset revealed that the simulated hybrid SVM
successfully classifies satellite images with accuracy comparable to the
classical SVM with the RBF kernel for large datasets. Interestingly, for large
datasets, the high accuracy was also observed for the simple quantum kernels,
lacking quantum entanglement.Comment: 12 pages, 10 figure
Przejścia fazowe w czterowymiarowym modelu CDT na torusie
Sformułowanie poprawnej teorii kwantowej grawitacji, która łączyłaby w sobie ogólną teorię względności oraz mechanikę kwantową wciąż pozostaje nierozwiązanym problemem fizyki. Wobec perturbacyjnej nierenormalizowalności grawitacji traktowanej konwencjonalnymi metodami teorii pola, podejmuje się próby innego skwantowania grawitacji. Jedną z nich są kauzalne dynamiczne triangulacje (CDT), które wykorzystują ideę całek po trajektoriach Feynmana i dyskretyzację czasoprzestrzeni poprzez konstruowanie jej z d-wymiarowych sympleksów. Otrzymany w ten sposób model statystyczny, może być badany w poszukiwaniu przejść fazowych, które mogłyby pomóc w znalezieniu granicy ciągłej teorii i poprawnym sformułowaniu kwantowej grawitacji. Praca zawiera wyniki badań dotyczących przejść fazowych w szczególności pomiędzy tzw. fazami B i Cb.The formulation of the correct quantum theory of gravity, which would combine General Relativity and Quantum Mechanics, remains an unresolved problem in physics. Due to the perturbational nonrenormalizability of gravity treated with conventional methods of field theory, attempts are made to quantize gravity in a different way. One of the methods are Causal Dynamical Triangulations (CDT), which use the idea of Feynman's path integral and discretization of space-time by constructing it from d-dimensional simplices. The statistical model obtained in this way can be examined in the search of phase transitions, which could help to find the continuum limit of the theory and the correct formulation of quantum gravity. The thesis contains results of a research on phase transitions, in particular between the so-called phases B and Cb
Quantum variational solving of the Wheeler-DeWitt equation
One of the central difficulties in the quantization of the gravitational
interactions is that they are described by a set of constraints. The standard
strategy for dealing with the problem is the Dirac quantization procedure,
which leads to the Wheeler-DeWitt equation. However, solutions to the equation
are known only for specific symmetry-reduced systems, including models of
quantum cosmology. Novel methods, which enable solving the equation for complex
gravitational configurations are, therefore, worth seeking.
Here, we propose and investigate a new method of solving the Wheeler-DeWitt
equation, which employs a variational quantum computing approach, and is
possible to implement on quantum computers. For this purpose, the gravitational
system is regularized, by performing spherical compactification of the phase
space. This makes the system's Hilbert space finite-dimensional and allows to
use variables, which are easy to handle in quantum computing. The
validity of the method is examined in the case of the flat de Sitter universe.
For the purpose of testing the method, both an emulator of a quantum computer
and the IBM superconducting quantum computer have been used. The advantages and
limitations of the approach are discussed.Comment: 15 page