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While world models learn compact representations of complex environments, they lack a physics-grounded metric to assess the structural fidelity of their latent spaces. We identify the wavelet scaling exponent $\alpha$ as a critical…

Quantum Physics · Physics 2026-05-13 Chon-Fai Kam , Xavier Cadet , Miloud Bessafi , Frederic Cadet

We propose a variational quantum eigensolver suitable for exploring the phase structure of the multi-flavor Schwinger model in the presence of a chemical potential. The parametric ansatz circuit we design is capable of incorporating the…

Quantum hardware is advancing rapidly across various platforms, yet implementing large-scale quantum error correction (QEC) remains challenging. As hardware continues to improve, there is a growing need to identify potential applications on…

Quantum Physics · Physics 2025-08-04 Gyungmin Cho , Dohun Kim

We ask whether the optimal probe is entangled, and if so, what is its character and amount, for estimating the noise parameter of a large class of local quantum encoding processes that we refer to as vector encoding, examples of which…

Quantum Physics · Physics 2026-04-23 Shuva Mondal , Priya Ghosh , Ujjwal Sen

Quasi-probability decompositions (QPDs) have proven essential in many quantum algorithms and protocols -- one replaces a ``difficult'' quantum circuit with an ensemble of ``easier'' circuit variants whose weighted outcomes reproduce any…

Quantum Physics · Physics 2026-02-13 Joshua W. Dai , Bálint Koczor

We propose an $N$-photon Gaussian measurement scheme which allows the estimation of a parameter $\varphi$ encoded into a multi-port interferometer with a Heisenberg scaling precision (i.e. of order $1/N$). In this protocol, no restrictions…

Quantum Physics · Physics 2021-12-23 Giovanni Gramegna , Danilo Triggiani , Paolo Facchi , Frank A. Narducci , Vincenzo Tamma

We consider a distributed sensor network in which the single antenna sensor nodes observe a deterministic unknown parameter and after encoding the observed signal with a phase parameter, the sensor nodes transmit it simultaneously to a…

Information Theory · Computer Science 2012-01-04 Feng Jiang , Jie Chen , A. Lee Swindlehurst

Optimization of unitary transformations in Variational Quantum Algorithms benefits highly from efficient evaluation of cost function gradients with respect to amplitudes of unitary generators. We propose several extensions of the…

Quantum Physics · Physics 2022-01-12 Artur F. Izmaylov , Robert A. Lang , Tzu-Ching Yen

Using a single quantum probe to sense other quantum objects offers distinct advantages but suffers from some limitations that may degrade the sensing precision severely, especially when the probe-target coupling is weak. Here we propose a…

Quantum Physics · Physics 2018-07-10 Yi-Nan Fang , Xing Xiao , Chang-Pu Sun , Wen Yang , Nan Zhao

We address the characterization of classical fractional random noise via quantum probes. In particular, we focus on estimation and discrimination problems involving the fractal dimension of the trajectories of a system subject to fractional…

Quantum Physics · Physics 2015-06-18 Matteo G. A. Paris

We experimentally investigate the viability of a variational quantum gate optimization protocol informed by the underlying physical Hamiltonian of fixed-frequency transmon qubits. The utility of the scheme is demonstrated through the…

Quantum Physics · Physics 2024-07-02 Sean Greenaway , Francesco Petiziol , Hongzheng Zhao , Florian Mintert

Evaluating the entanglement spectrum is essential for characterizing exotic quantum phases such as quantum criticality and topological order. However, for large quantum many-body systems, this task is hindered by the exponential measurement…

Quantum Physics · Physics 2026-05-12 Shohei Miyakoshi , Takanori Sugimoto , Tomonori Shirakawa , Seiji Yunoki , Hiroshi Ueda

An efficient implementation of the Toffoli gate is of conceptual importance for running various quantum algorithms, including Grover's search and Shor's integer factorization. However, direct implementation of the Toffoli gate either…

We present a scalable method for learning local quantum channels using local expectation values measured on a single state -- their steady state. Our method is inspired by the algorithms for learning local Hamiltonians from their ground…

Quantum Physics · Physics 2024-07-12 Yigal Ilin , Itai Arad

The minimum achievable statistical uncertainty in the estimation of physical parameters is determined by the quantum Fisher information. Its computation for noisy systems is still a challenging problem. Using a variational approach, we…

Quantum Physics · Physics 2012-11-21 B. M. Escher , L. Davidovich , N. Zagury , R. L. de Matos Filho

Quantum phase estimation~(QPE) is central to numerous quantum algorithms, yet its standard implementation demands an $\calO(m^{2})$-gate quantum Fourier transform~(QFT) on $m$ control qubits-a prohibitive overhead on near-term noisy…

Quantum Physics · Physics 2026-04-08 Akoramurthy B , Surendiran. B

We unify Ramsey, twist-untwist, and random quantum sensors using operator algebra and account for the Fisher scaling of various sensor designs. We illustrate how the operator orbits associated with state preparation inform the scaling of…

Quantum Physics · Physics 2025-12-16 Sooryansh Asthana , Yeshma Ibrahim , Norman Tze Wei Koo , Sai Vinjanampathy

Experimental characterizations of a quantum system involve the measurement of expectation values of observables for a preparable state |psi> of the quantum system. Such expectation values can be measured by repeatedly preparing |psi> and…

Quantum Physics · Physics 2009-11-13 Emanuel Knill , Gerardo Ortiz , Rolando D. Somma

Production and verification of multipartite quantum state are an essential step in quantum information processing. In this work, we propose an efficient method to decompose symmetric multipartite observables, which are invariant under…

Quantum Physics · Physics 2019-05-21 You Zhou , Chenghao Guo , Xiongfeng Ma

Under ideal conditions, quantum metrology promises a precision gain over classical techniques scaling quadratically with the number of probe particles. At the same time, no-go results have shown that generic, uncorrelated noise limits the…

Quantum Physics · Physics 2017-07-13 J. B. Brask , R. Chaves , J. Kolodynski
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