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Performing experiments on small-scale quantum computers is certainly a challenging endeavor. Many parameters need to be optimized to achieve high-fidelity operations. This can be done efficiently for operations acting on single qubits as…

Quantum Physics · Physics 2016-08-31 M. Müller , A. Rivas , E. A. Martínez , D. Nigg , P. Schindler , T. Monz , R. Blatt , M. A. Martin-Delgado

Quantum combs play a vital role in characterizing and transforming quantum processes, with wide-ranging applications in quantum information processing. However, obtaining the explicit quantum circuit for the desired quantum comb remains a…

Quantum Physics · Physics 2025-02-26 Yin Mo , Lei Zhang , Yu-Ao Chen , Yingjian Liu , Tengxiang Lin , Xin Wang

Quantum state tomography is a central technique for the characterization and verification of quantum systems. Standard tomography is widely used for low-dimensional systems, but for larger systems, it becomes impractical due to the…

Several Bayesian estimation based heuristics have been developed to perform quantum state tomography (QST). Their ability to quantify uncertainties using region estimators and include a priori knowledge of the experimentalists makes this…

Quantum Physics · Physics 2021-09-16 Syed Muhammad Kazim , Ahmad Farooq , Junaid ur Rehman , Hyundong Shin

We have performed an experiment demonstrating that loop state-preparation-and-measurement (SPAM) tomography [C. Jackson and S. J. van Enk, Phys. Rev. A 92, 042312 (2015)] is capable of detecting correlated errors between the preparation and…

Quantum Physics · Physics 2017-04-21 A. F. McCormick , S. J. van Enk , M. Beck

The rapid advancement of quantum hardware necessitates the development of reliable methods to certify its correct functioning. However, existing certification tests fall short, as they either suffer from systematic errors or do not…

Quantum Physics · Physics 2025-08-13 Jan Nöller , Nikolai Miklin , Martin Kliesch , Mariami Gachechiladze

Characterizing quantum systems is a fundamental task that enables the development of quantum technologies. Various approaches, ranging from full tomography to instances of classical shadows, have been proposed to this end. However, quantum…

Quantum Physics · Physics 2025-06-16 Franz J. Schreiber , Jens Eisert , Johannes Jakob Meyer

To push gate performance to levels beyond the thresholds for quantum error correction, it is important to characterize the error sources occurring on quantum gates. However, the characterization of non-Markovian error poses a challenge to…

Scalable characterization of quantum processors is crucial for mitigating noise and imperfections. While randomized measurement protocols enable efficient access to local observables, inferring a globally consistent description of…

Quantum Physics · Physics 2026-03-10 Zidu Liu , Dominik S. Wild

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

The accurate and reliable description of measurement devices is a central problem in both observing uniquely non-classical behaviors and realizing quantum technologies from powerful computing to precision metrology. To date quantum…

Quantum Physics · Physics 2020-01-30 Aonan Zhang , Jie Xie , Huichao Xu , Kaimin Zheng , Han Zhang , Yiu-Tung Poon , Vlatko Vedral , Lijian Zhang

Quantum computing is an emerging technology that has the potential to revolutionize fields such as cryptography, machine learning, optimization, and quantum simulation. However, a major challenge in the realization of quantum algorithms on…

Quantum Physics · Physics 2023-01-31 Robert Wille , Lukas Burgholzer

A reliable method for characterizing quantum operations that is suitable for improving and validating their accuracies is indispensable for realizing a practical quantum computer. Known methods are still not sufficient because they lack…

Quantum Physics · Physics 2021-06-25 Takanori Sugiyama , Shinpei Imori , Fuyuhiko Tanaka

Standard compilers for quantum circuits decompose arbitrary single-qubit gates into a sequence of physical X(pi/2) pulses and virtual-Z phase gates. Consequently, many circuit classes implement different logic operations but have an…

A new method of quantum state tomography for quantum information processing is described. The method based on two-dimensional Fourier transform technique involves detection of all the off-diagonal elements of the density matrix in a…

Quantum Physics · Physics 2009-11-07 Ranabir Das , T. S. Mahesh , Anil Kumar

Full connectivity of qubits is necessary for most quantum algorithms, which is difficult to directly implement on Noisy Intermediate-Scale Quantum processors. However, inserting swap gate to enable the two-qubit gates between uncoupled…

Quantum Physics · Physics 2021-02-03 Bin-Han Lu , Yu-Chun Wu , Wei-Cheng Kong , Qi Zhou , Guo-Ping Guo

Quantum processors may enhance machine learning by mapping high-dimensional data onto quantum systems for processing. Conventional feature maps, for encoding data onto a quantum circuit are currently impractical, as the number of entangling…

Quantum Physics · Physics 2026-03-27 Utkarsh Singh , Jean-Frédéric Laprade , Aaron Z. Goldberg , Khabat Heshami

The characterization of quantum dynamics is a fundamental and central task in quantum mechanics. This task is typically addressed by quantum process tomography (QPT). Here we present an alternative "direct characterization of quantum…

Quantum Physics · Physics 2007-05-23 M. Mohseni , D. A. Lidar

To execute quantum circuits on a quantum processor, they must be modified to meet the physical constraints of the quantum device. This process, called quantum circuit mapping, results in a gate/circuit depth overhead that depends on both…

Quantum Physics · Physics 2024-01-10 Medina Bandić , Carmen G. Almudever , Sebastian Feld

In the noisy intermediate-scale quantum (NISQ) era, quantum error mitigation (QEM) is essential for producing reliable outputs from quantum circuits. We present a statistical signal processing approach to QEM that estimates the most likely…