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We discuss a model for quantum computing with initially mixed states. Although such a computer is known to be less powerful than a quantum computer operating with pure (entangled) states, it may efficiently solve some problems for which no…

Quantum Physics · Physics 2015-03-17 Michael Siomau , Stephan Fritzsche

Quantum computing is a growing field where the information is processed by two-levels quantum states known as qubits. Current physical realizations of qubits require a careful calibration, composed by different experiments, due to noise and…

Quantum Physics · Physics 2023-09-15 Edoardo Pedicillo , Andrea Pasquale , Stefano Carrazza

Applications of quantum mechanics rely on the accuracy of reading and writing data. This requires accurate measurements and preparations of the quantum states. I show that accurate measurements and preparations are impossible if the total…

Quantum Physics · Physics 2025-10-06 Ovidiu Cristinel Stoica

For the first time in history, we are seeing a branching point in computing paradigms with the emergence of quantum processing units (QPUs). Extracting the full potential of computation and realizing quantum algorithms with a…

Quantum Physics · Physics 2022-11-29 Sergey Bravyi , Oliver Dial , Jay M. Gambetta , Dario Gil , Zaira Nazario

A new model of quantum computation is considered, in which the connections between gates are programmed by the state of a quantum register. This new model of computation is shown to be more powerful than the usual quantum computation, e. g.…

Quantum Physics · Physics 2013-05-27 Timoteo Colnaghi , Giacomo Mauro D'Ariano , Paolo Perinotti , Stefano Facchini

Quantum measurement is universal for quantum computation. This universality allows alternative schemes to the traditional three-step organisation of quantum computation: initial state preparation, unitary transformation, measurement. In…

Quantum Physics · Physics 2007-05-23 Simon Perdrix , Philippe Jorrand

To observe or control a quantum system, one must interact with it via an interface. This letter exhibits simple universal quantum interfaces--quantum input/output ports consisting of a single two-state system or quantum bit that interacts…

Quantum Physics · Physics 2007-05-23 Seth Lloyd , Andrew J. Landahl , Jean-Jacques E. Slotine

According to the statistical interpretation of quantum theory, quantum computers form a distinguished class of probabilistic machines (PMs) by encoding n qubits in 2n pbits (random binary variables). This raises the possibility of a…

Quantum Physics · Physics 2007-05-23 P. Gralewicz

In the medium term, quantum computing must tackle two key challenges: fault tolerance and security. Fault tolerance will be solved with sufficiently high quality experiments on large numbers of qubits, but the scale and complexity of these…

Quantum Physics · Physics 2024-04-11 Ethan Davies , Alastair Kay

A universal quantum computing scheme, with a universal set of logical gates, is proposed based on networks of 1D quantum systems. The encoding of information is in terms of universal features of gapped phases, for which effective field…

Quantum Physics · Physics 2019-07-24 Dong-Sheng Wang

Quantum tomography is the main method used to assess the quality of quantum information processing devices, but its complexity presents a major obstacle for the characterization of even moderately large systems. The number of experimental…

Quantum Physics · Physics 2015-03-19 Marcus P. da Silva , Olivier Landon-Cardinal , David Poulin

Quantum information is a rapidly advancing area of interdisciplinary research. It may lead to real-world applications for communication and computation unavailable without the exploitation of quantum properties such as nonorthogonality or…

Quantum Physics · Physics 2009-11-10 Samuel L. Braunstein , Peter van Loock

Quantum computing is an emerging technology with potentially far-reaching implications for national prosperity and security. Understanding the timeframes over which economic benefits and national security risks may manifest themselves is…

Future quantum computers are anticipated to be able to perform simulations of quantum many-body systems and quantum field theories that lie beyond the capabilities of classical computation. This will lead to new insights and predictions for…

Nuclear Theory · Physics 2023-12-14 Martin J. Savage

Quantum measurement is universal for quantum computation. This universality allows alternative schemes to the traditional three-step organisation of quantum computation: initial state preparation, unitary transformation, measurement. In…

Quantum Physics · Physics 2016-09-08 Simon Perdrix , Philippe Jorrand

The quantum circuit model is the most widely used model of quantum computation. It provides both a framework for formulating quantum algorithms and an architecture for the physical construction of quantum computers. However, several other…

Quantum Physics · Physics 2008-09-16 Stephen P. Jordan

A quantum processor, like any computing device, requires the development of both hardware and the necessary set of software solutions, starting with quantum algorithms and ending with means of accessing quantum devices. As part of the…

Quantum computers are expected to offer substantial speedups over their classical counterparts and to solve problems that are intractable for classical computers. Beyond such practical significance, the concept of quantum computation opens…

Quantum Physics · Physics 2014-11-13 Stefanie Barz , Joseph F. Fitzsimons , Elham Kashefi , Philip Walther

Quantum information refers to the distinctive information-processing properties of quantum systems, which arise when information is stored in or retrieved from nonorthogonal quantum states. More information is required to prepare an…

Quantum Physics · Physics 2007-05-23 Carlton M. Caves , Christopher A. Fuchs

Quantum computing is poised to redefine the algorithmic foundations of communication systems. While quantum superposition and entanglement enable quadratic or exponential speedups for specific problems, identifying use cases where these…

Signal Processing · Electrical Eng. & Systems 2025-12-10 Naoki Ishikawa , Giuseppe Thadeu Freitas de Abreu , Petar Popovski , Robert W. Heath