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We extend Pearl's definition of causal influence to the quantum domain, where two quantum systems $A$, $B$ with finite-dimensional Hilbert space are embedded in a common environment $C$ and propagated with a joint unitary $U$. For finite…

Quantum Physics · Physics 2022-12-28 Llorenç Escolà-Farràs , Daniel Braun

Entanglement is a physical resource of a quantum system just like mass, charge or energy. Moreover it is an essential tool for many purposes of nowadays quantum information processing, e.g. quantum teleportation, quantum cryptography or…

Disordered Systems and Neural Networks · Physics 2008-02-15 Imre Varga , Jose Antonio Mendez-Bermudez

Causal influences are at the core of any empirical science, the reason why its quantification is of paramount relevance for the mathematical theory of causality and applications. Quantum correlations, however, challenge our notion of cause…

Quantum Physics · Physics 2023-09-20 Lucas Hutter , Rafael Chaves , Ranieri Nery , George Moreno , Daniel J. Brod

Whether uniquely quantum resources confer advantages in fully classical, competitive environments remains an open question. Competitive zero-sum reinforcement learning is particularly challenging, as success requires modelling dynamic…

Quantum Physics · Physics 2026-03-12 Peiyong Wang , Kieran Hymas , James Quach

Expressibility is a crucial factor of a Parameterized Quantum Circuit (PQC). In the context of Variational Quantum Algorithms (VQA) based Quantum Machine Learning (QML), a QML model composed of highly expressible PQC and sufficient number…

Quantum Physics · Physics 2024-08-12 Yu Liu , Kentaro Baba , Kazuya Kaneko , Naoyuki Takeda , Junpei Koyama , Koichi Kimura

Parametric quantum circuits play a crucial role in the performance of many variational quantum algorithms. To successfully implement such algorithms, one must design efficient quantum circuits that sufficiently approximate the solution…

Quantum Physics · Physics 2021-05-05 Lena Funcke , Tobias Hartung , Karl Jansen , Stefan Kühn , Paolo Stornati

The restrictions that nature places on the distribution of correlations in a multipartite quantum system play fundamental roles in the evolution of such systems, and yield vital insights into the design of protocols for the quantum control…

Quantum Physics · Physics 2007-05-23 Tracey E. Tessier

With the advent of hybrid quantum classical algorithms using parameterized quantum circuits the question of how to optimize these algorithms and circuits emerges. In this paper we show that the number of single-qubit rotations in…

Quantum Physics · Physics 2020-10-29 S. E. Rasmussen , N. J. S. Loft , T. Bækkegaard , M. Kues , N. T. Zinner

Quantum tangent kernel methods provide an efficient approach to analyzing the performance of quantum machine learning models in the infinite-width limit, which is of crucial importance in designing appropriate circuit architectures for…

Quantum Physics · Physics 2023-11-10 Li-Wei Yu , Weikang Li , Qi Ye , Zhide Lu , Zizhao Han , Dong-Ling Deng

Parameterized quantum circuits (PQCs) have been broadly used as a hybrid quantum-classical machine learning scheme to accomplish generative tasks. However, whether PQCs have better expressive power than classical generative neural networks,…

Quantum Physics · Physics 2020-07-29 Yuxuan Du , Min-Hsiu Hsieh , Tongliang Liu , Dacheng Tao

We study quantum causal inference in a set-up proposed by Ried et al. [Nat. Phys. 11, 414 (2015)] in which a common-cause scenario can be mixed with a cause-effect scenario, and for which it was found that quantum mechanics can bring an…

Quantum Physics · Physics 2019-12-24 Jonas Kübler , Daniel Braun

When subject to a non-local unitary evolution, qubits in a quantum circuit become increasingly entangled. Conversely, measurements applied to individual qubits lead to their disentanglement from the collective system. The extent of…

Quantum Physics · Physics 2025-01-22 Sourav Manna , Vaibhav Madhok , Arul Lakshminarayan

In studies of entanglement, finding out if a state is entangled and quantifying the amount of entanglement contained in a state are related but different questions. Similarly in studies of causality, finding out the causal structures…

Quantum Physics · Physics 2018-01-22 Ding Jia

As an alternative to entanglement entropies, the capacity of entanglement becomes a promising candidate to probe and estimate the degree of entanglement of quantum bipartite systems. In this work, we study the typical behavior of…

Mathematical Physics · Physics 2023-01-24 Lu Wei

Quantum mechanics, in principle, allows for processes with indefinite causal order. However, most of these causal anomalies have not yet been detected experimentally. We show that every such process can be simulated experimentally by means…

Quantum Physics · Physics 2018-04-04 Simon Milz , Felix A. Pollock , Thao P. Le , Giulio Chiribella , Kavan Modi

Quantum computers can be used for supervised learning by treating parametrised quantum circuits as models that map data inputs to predictions. While a lot of work has been done to investigate practical implications of this approach, many…

Quantum Physics · Physics 2021-03-31 Maria Schuld , Ryan Sweke , Johannes Jakob Meyer

Whether parameterized quantum circuits (PQCs) can be systematically constructed to be both trainable and expressive remains an open question. Highly expressive PQCs often exhibit barren plateaus, while several trainable alternatives admit…

Quantum Physics · Physics 2026-03-17 Peter Röseler , Dennis Willsch , Kristel Michielsen

Quantum kernels are considered as potential resources to illustrate benefits of quantum computing in machine learning. Considering the impact of hyperparameters on the performance of a classical machine learning model, it is imperative to…

Quantum Physics · Physics 2023-08-09 Diksha Sharma , Parvinder Singh , Atul Kumar

Quantum computers can be considered as a natural means for performing machine learning tasks for inherently quantum labeled data. Many quantum machine learning techniques have been developed for solving classification problems, such as…

Quantum Physics · Physics 2025-01-24 Andrey Kardashin , Yerassyl Balkybek , Vladimir V. Palyulin , Konstantin Antipin

Causal inference revealing causal dependencies between variables from empirical data has found applications in multiple sub-fields of scientific research. A quantum perspective of correlations holds the promise of overcoming the limitation…