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A generic qubit unitary operator affected by depolarizing noise is duplicated and inserted in a quantum switch process realizing a superposition of causal orders. The characterization of the resulting switched quantum channel is worked out…

Quantum Physics · Physics 2021-04-14 Francois Chapeau-Blondeau

Quantum sampling, a fundamental subroutine in numerous quantum algorithms, involves encoding a given probability distribution in the amplitudes of a pure state. Given the hefty cost of large-scale quantum storage, we initiate the study of…

Quantum Physics · Physics 2025-06-10 Longyun Chen , Jingcheng Liu , Penghui Yao

Many prominent quantum computing algorithms with applications in fields such as chemistry and materials science require a large number of measurements, which represents an important roadblock for future real-world use cases. We introduce a…

This paper presents a quantum algorithm for efficiently computing partial sums and specific weighted partial sums of quantum state amplitudes. Computation of partial sums has important applications, including numerical integration,…

Quantum Physics · Physics 2025-07-15 Alok Shukla , Prakash Vedula

While quantum speed-up in solving certain decision problems by a fault-tolerant universal quantum computer has been promised, a timely research interest includes how far one can reduce the resource requirement to demonstrate a provable…

Quantum Physics · Physics 2018-01-01 Jacob Miller , Stephen Sanders , Akimasa Miyake

Understanding what can be learned from experiments is central to scientific progress. In this work, we use a learning-theoretic perspective to study the task of learning physical operations in a quantum machine when all operations (state…

Quantum Physics · Physics 2022-04-29 Hsin-Yuan Huang , Steven T. Flammia , John Preskill

This paper explores a fine-grained version of the Watrous conjecture, including the randomized and quantum algorithms with success probabilities arbitrarily close to $1/2$. Our contributions include the following: i) An analysis of the…

Computational Complexity · Computer Science 2023-10-24 Supartha Podder , Penghui Yao , Zekun Ye

The estimation of multi-qubit observables is a key task in quantum information science. The standard approach is to decompose a multi-qubit observable into a weighted sum of Pauli strings. The observable can then be estimated from…

Quantum Physics · Physics 2023-09-01 L. A. Markovich , J. Borregaard

In quantum information, most information processing processes involve quantum channels. One manifestation of a quantum channel is quantum operation acting on quantum states. The coherence of quantum operations can be considered as a quantum…

Quantum Physics · Physics 2022-11-23 Xiaorong Wang , Ting Gao , Fengli Yan

The general adversary dual is a powerful tool in quantum computing because it gives a query-optimal bounded-error quantum algorithm for deciding any Boolean function. Unfortunately, the algorithm uses linear qubits in the worst case, and…

Quantum Physics · Physics 2023-06-28 Michael Czekanski , Shelby Kimmel , R. Teal Witter

Quantum amplitude estimation is a key sub-routine of a number of quantum algorithms with various applications. We propose an adaptive algorithm for interval estimation of amplitudes. The quantum part of the algorithm is based only on…

Quantum Physics · Physics 2022-06-20 Yunpeng Zhao , Haiyan Wang , Kuai Xu , Yue Wang , Ji Zhu , Feng Wang

This paper presents a quantum algorithm for solving the fractional Poisson equation \((-\Delta)^s u = f\) with \(s \in (0,1)\) on bounded domains. The proposed approach combines rational approximation techniques with quantum linear system…

Quantum Physics · Physics 2026-04-02 Yin Yang , Yue Yu , Long Zhang , Ming Zhou

We introduce the problem of unitarization. Unitarization is the problem of taking $k$ input quantum circuits that produce orthogonal states from the all $0$ state, and create an output circuit implementing a unitary with its first $k$…

Quantum Physics · Physics 2021-09-15 Joshua Cook

We propose a quantum machine learning algorithm for efficiently solving a class of problems encoded in quantum controlled unitary operations. The central physical mechanism of the protocol is the iteration of a quantum time-delayed equation…

We address the problem of quantum reading of optical memories, namely the retrieving of classical information stored in the optical properties of a media with minimum energy. We present optimal strategies for ambiguous and unambiguous…

Quantum Physics · Physics 2015-02-23 Michele Dall'Arno , Alessandro Bisio , Giacomo Mauro D'Ariano

One limitation of the variational quantum eigensolver algorithm is the large number of measurement steps required to estimate different terms in the Hamiltonian of interest. Unitary partitioning reduces this overhead by transforming the…

Quantum Physics · Physics 2021-09-01 Alexis Ralli , Peter Love , Andrew Tranter , Peter Coveney

Universal compilation is a training process that compiles a trainable unitary into a target unitary and it serves vast potential applications from quantum dynamic simulations to optimal circuits with deep-compressing, device benchmarking,…

Quantum Physics · Physics 2022-04-26 Vu Tuan Hai , Le Bin Ho

While the power of quantum computers is commonly acknowledged to rise exponentially, it is often overlooked that the complexity of quantum noise mechanisms generally grows much faster. In particular, quantifying whether the instructions on…

Quantum Physics · Physics 2024-09-04 Pedro Figueroa-Romero , Miha Papič , Adrian Auer , Inés de Vega

The quantification of the quantumness of a quantum ensemble has theoretical and practical significance in quantum information theory. We propose herein a class of measures of the quantumness of quantum ensembles using the unitary similarity…

Quantum Physics · Physics 2018-03-28 Xianfei Qi , Ting Gao , Fengli Yan

Perceptrons, which perform binary classification, are the fundamental building blocks of neural networks. Given a data set of size~$N$ and margin~$\gamma$ (how well the given data are separated), the query complexity of the best-known…

Quantum Physics · Physics 2025-05-14 Pengcheng Liao , Barry C. Sanders , Tim Byrnes