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Decoherence is believed to deteriorate the ability of a purification scheme that is based on the idea of driving a system to a pure state by repeatedly measuring another system in interaction with the former and hinder for a pure state to…

Quantum Physics · Physics 2008-04-23 H. Nakazato , K. Yuasa , B. Militello , A. Messina

The class of commuting quantum circuits known as IQP (instantaneous quantum polynomial-time) has been shown to be hard to simulate classically, assuming certain complexity-theoretic conjectures. Here we study the power of IQP circuits in…

Quantum Physics · Physics 2017-04-26 Michael J. Bremner , Ashley Montanaro , Dan J. Shepherd

I present an explicit classical simulation of arbitrary quantum noise for quantum models in which one qubit interacts with a quantum bath. The classical model simulates the interaction of the bath and the qubit by random unitary evolutions.…

Quantum Physics · Physics 2017-11-01 Seyyed M. H. Halataei

This study explores the challenge of improving multiclass image classification through quantum machine-learning techniques. It explores how the discarded qubit states of Noisy Intermediate-Scale Quantum (NISQ) quantum convolutional neural…

Quantum Physics · Physics 2025-08-26 Shuchismita Anwar , Sowmitra Das , Muhammad Iqbal Hossain , Jishnu Mahmud

An ideal system of $n$ qubits has $2^n$ dimensions. This exponential grants power, but also hinders characterizing the system's state and dynamics. We study a new problem: the qubits in a physical system might not be independent. They can…

Quantum Physics · Physics 2018-10-19 Rui Chao , Ben W. Reichardt , Chris Sutherland , Thomas Vidick

We consider the problem of correctly classifying a given quantum two-level system (qubit) which is known to be in one of two equally probable quantum states. We assume that this task should be performed by a quantum machine which does not…

Quantum Physics · Physics 2019-07-02 Marco Fanizza , Andrea Mari , Vittorio Giovannetti

Quantum algorithms are known for presenting more efficient solutions to certain computational tasks than any corresponding classical algorithm. It has been thought that the origin of the power of quantum computation has its roots in…

Quantum Entanglement is a fundamentally important resource in Quantum Information Science; however, generating it in practice is plagued by noise and decoherence, limiting its utility. Entanglement distillation and forward error correction…

Quantum Physics · Physics 2023-07-14 Vaishnavi L. Addala , Shu Ge , Stefan Krastanov

The no-cloning theorem forbids the creation of identical copies of qubits, thereby imposing strong limitations on quantum technologies. A recently-proposed protocol, encrypted cloning, showed, however, that the creation of perfect clones is…

In this paper we consider the purification of a quantum state using the information obtained from a continuous measurement record, where the classical measurement record is digitized to a single bit per measurement after the measurements…

Quantum Physics · Physics 2012-01-05 Jason F. Ralph , Neil P. Oxtoby

It has recently been shown that there are efficient algorithms for quantum computers to solve certain problems, such as prime factorization, which are intractable to date on classical computers. The chances for practical implementation,…

Quantum Physics · Physics 2009-10-30 Adriano Barenco , Todd A. Brun , Ruediger Schack , Tim Spiller

We develop Monte Carlo methods for sampling random states and corresponding bit strings in qubit systems. To this end, we derive exact probability density functions that yield the Porter-Thomas distribution in the limit of large systems. We…

Quantum Physics · Physics 2025-09-05 Andreas Raab

Quantum circuit simulators running on classical computers offer a vital platform for designing, testing, and optimizing quantum algorithms, driving innovation despite limited access to real quantum hardware. However, their scalability is…

Quantum Physics · Physics 2025-10-29 Gleb Kalachev , Pavel Mosharev , Zuoheng Zou , Pavel Panteleev , Man-Hong Yung

When various observers obtain information in an independent fashion about a classical system, there is a simple rule which allows them to pool their knowledge, and this requires only the states-of-knowledge of the respective observers. Here…

Quantum Physics · Physics 2009-11-11 Kurt Jacobs

The goal of qubit purification is to combine multiple noisy copies of an unknown pure quantum state to obtain one or more copies that are closer to the pure state. We show that a simple protocol based solely on random SWAP tests achieves…

Quantum Physics · Physics 2025-12-23 Shrigyan Brahmachari , Austin Hulse , Henry D. Pfister , Iman Marvian

A quantum processing unit (QPU) must contain a large number of high quality qubits to produce accurate results for problems at useful scales. In contrast, most scientific and industry classical computation workloads happen in parallel on…

Emerging Technologies · Computer Science 2025-02-06 Wei Tang , Margaret Martonosi

We propose an approach to generative quantum machine learning that overcomes the fundamental scaling issues of variational quantum circuits. The core idea is to use a class of generative models based on instantaneous quantum polynomial…

Quantum Physics · Physics 2026-02-09 Erik Recio-Armengol , Shahnawaz Ahmed , Joseph Bowles

Quantum algorithms are known for providing more efficient solutions to certain computational tasks than any corresponding classical algorithm. Here we show that a single qudit is sufficient to implement an oracle based quantum algorithm,…

There is a large body of work studying what forms of computational hardness are needed to realize classical cryptography. In particular, one-way functions and pseudorandom generators can be built from each other, and thus require equivalent…

Cryptography and Security · Computer Science 2025-04-02 Bruno Cavalar , Eli Goldin , Matthew Gray , Peter Hall , Yanyi Liu , Angelos Pelecanos

We assess the effects of an intrinsic model for imperfections in cluster states by introducing {\it noisy cluster states} and characterizing their role in the one-way model for quantum computation. The action of individual dephasing…

Quantum Physics · Physics 2013-12-25 M. S. Tame , M. Paternostro , M. S. Kim , V. Vedral
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