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Randomised measurements can efficiently characterise many-body quantum states by learning the expectation values of observables with low Pauli weights. In this paper, we generalise the theoretical tools of classical shadow tomography to the…

Quantum Physics · Physics 2026-02-05 Gregory A. L. White , Lloyd C. L. Hollenberg , Charles D. Hill , Kavan Modi

Universal control of quantum systems is a major goal to be achieved for quantum information processing, which demands thorough understanding of fundamental quantum mechanics and promises applications of quantum technologies. So far, most…

Quantum Physics · Physics 2019-02-05 Ling Hu , Xianghao Mu , Weizhou Cai , Yuwei Ma , Yuan Xu , Haiyan Wang , YiPu Song , Chang-Ling Zou , Luyan Sun

We review in a unified way a recently proposed method to detect properties of unknown quantum channels and lower bounds to quantum capacities, without resorting to full quantum process tomography. The method is based on the preparation of a…

Quantum Physics · Physics 2017-12-19 Chiara Macchiavello , Massimiliano F. Sacchi

Quantum computation has been growing rapidly in both theory and experiments. In particular, quantum computing devices with a large number of qubits have been developed by IBM, Google, IonQ, and others. The current quantum computing devices…

Quantum Physics · Physics 2021-02-10 Rishabh Gupta , Rongxin Xia , Raphael D. Levine , Sabre Kais

Quantum Process Tomography (QPT) methods aim at identifying, i.e. estimating, a quantum process. QPT is a major quantum information processing tool, since it especially allows one to experimentally characterize the actual behavior of…

Quantum Physics · Physics 2025-06-27 Yannick Deville , Alain Deville

The development of emerging technologies in quantum optics demands accurate models that faithfully capture genuine quantum effects. Mature semiclassical approaches reach their limits when confronted with quantized electromagnetic fields,…

Quantum state tomography is an essential component of modern quantum technology. In application to continuous-variable harmonic-oscilator systems, such as the electromagnetic field, existing tomography methods typically reconstruct the…

Quantum Physics · Physics 2023-01-09 Ekaterina Fedotova , Nikolai Kuznetsov , Egor Tiunov , A. E. Ulanov , A. I. Lvovsky

Quantum metrology concerns improving the estimation of an unknown parameter using an optimal measurement scheme on the quantum system. More the optimality of the measurement, the better will be the improvement in sensing the value of the…

Quantum Physics · Physics 2025-07-30 H. S. Karthik

We use quantum process tomography to characterize a full universal set of all-microwave gates on two superconducting single-frequency single-junction transmon qubits. All extracted gate fidelities, including those for Clifford group…

Random (mixed) unitary channels describe an important subset of quantum channels, which are commonly used in quantum information, noise modeling, and quantum error mitigation. Despite their usefulness, there is substantial complexity in…

Quantum Physics · Physics 2025-01-30 Scott E. Smart , Alexander Jürgens , Joseph Peetz , Prineha Narang

We investigate the problem of predicting the output behavior of unknown quantum channels. Given query access to an $n$-qubit channel $E$ and an observable $O$, we aim to learn the mapping \begin{equation*} \rho \mapsto \mathrm{Tr}(O…

Quantum Physics · Physics 2024-09-06 Sitan Chen , Jaume de Dios Pont , Jun-Ting Hsieh , Hsin-Yuan Huang , Jane Lange , Jerry Li

Quantum state tomography is a powerful, but resource-intensive, general solution for numerous quantum information processing tasks. This motivates the design of robust tomography procedures that use relevant resources as sparingly as…

Quantum Physics · Physics 2022-01-17 Fernando G. S. L. Brandão , Richard Kueng , Daniel Stilck França

Quantum state tomography (QST), the process of reconstructing some unknown quantum state $\hat\rho$ from repeated measurements on copies of said state, is a foundationally important task in the context of quantum computation and simulation.…

Quantum Physics · Physics 2025-10-21 Nathan Keenan , John Goold , Alex Nico-Katz

Model-independent estimation of the properties of quantum states is a central challenge in quantum technologies, as experimental imperfections, drifts, and imprecise models of the actual quantum dynamics inevitably hinder accurate…

Encoding quantum information into superpositions of multiple Fock states of a harmonic oscillator can provide protection against errors, but it comes with the cost of requiring more complex quantum gates that need to address multiple Fock…

In order to achieve fault-tolerant quantum computation, we need to repeat the following sequence of four steps: First, perform 1 or 2 qubit quantum gates (in parallel if possible). Second, do a syndrome measurement on a subset of the…

Quantum Physics · Physics 2024-12-11 Harry Buhrman , Marten Folkertsma , Bruno Loff , Niels M. P. Neumann

A convex optimization based method is proposed for quantum process tomography, in the case of known channel model structure, but unknown channel parameters. The main idea is to select an affine parametrization of the Choi matrix as a set of…

Quantum Physics · Physics 2010-04-30 Gábor Balló , Katalin M. Hangos

The ability of implementing quantum operations plays fundamental role in manipulating quantum systems. Creation and annihilation operators which transform a quantum state to another by adding or subtracting a particle are crucial of…

Quantum Physics · Physics 2019-05-01 Xiangyu Kong , Shijie Wei , Jingwei Wen , Guilu Long

Anomaly detection is an important problem with applications in various domains such as fraud detection, pattern recognition or medical diagnosis. Several algorithms have been introduced using classical computing approaches. However, using…

Machine Learning · Computer Science 2024-10-10 Robin Frehner , Kurt Stockinger

Quantum information has been drawing a wealth of research in recent years, shedding light on questions at the heart of quantum mechanics, as well as advancing fields such as complexity theory, cryptography, key distribution, and chemistry.…

Quantum Physics · Physics 2017-04-25 Dikla Oren , Maor Mutzafi , Yonina C. Eldar , Mordechai Segev