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Interconnecting well-functioning, scalable stationary qubits and photonic qubits could substantially advance quantum communication applications and serve to link future quantum processors. Here, we present two protocols for transferring the…

Two schemes for sharing an arbitrary two-qubit state based on entanglement swapping are proposed with Bell-state measurements and local unitary operations. One is based on the quantum channel with four Einstein-Podolsky-Rosen (EPR) pairs…

Quantum Physics · Physics 2009-11-11 Fu-Guo Deng , Xi-Han Li , Chun-Yan Li , Ping Zhou , Hong-Yu Zhou

A quantum state is called concordant if it has zero quantum discord with respect to any part. By extension, a concordant computation is one such that the state of the computer, at each time step, is concordant. In this paper, I describe a…

Quantum Physics · Physics 2010-06-24 Bryan Eastin

Image-based data is a popular arena for testing quantum machine learning algorithms. A crucial factor in realizing quantum advantage for these applications is the ability to efficiently represent images as quantum states. Here we present a…

Quantum Physics · Physics 2023-10-10 Jason Iaconis , Sonika Johri

Entanglement is a fundamental property of quantum mechanics, and is a primary resource in quantum information systems. Its manipulation remains a central challenge in the development of quantum technology. In this work, we demonstrate a…

Quantum state tomography, the ability to deduce the state of a quantum system from measured data, is the gold standard for verification and benchmarking of quantum devices. It has been realized in systems with few components, but for larger…

As quantum technologies mature, the development of tools for benchmarking their ability to prepare and manipulate complex quantum states becomes increasingly necessary. A key concept, the state overlap between two quantum states, offers a…

Quantum Physics · Physics 2021-12-23 Leonardo Guerini , Roeland Wiersema , Juan Felipe Carrasquilla , Leandro Aolita

The optimal estimation of a quantum mechanical 2-state system (qubit) - with N identically prepared qubits available - is obtained by measuring all qubits simultaneously in an entangled basis. We report the experimental estimation of qubits…

Quantum Physics · Physics 2007-05-23 Th. Hannemann , D. Reiss , Ch. Balzer , W. Neuhauser , P. E. Toschek , Ch. Wunderlich

Quantum computing employs controllable interactions to perform sequences of logical gates and entire algorithms on quantum registers. This paradigm has been widely explored, e.g., for simulating dynamics of manybody systems by decomposing…

Quantum Physics · Physics 2025-05-21 S. Alipour , A. T. Rezakhani , Alireza Tavanfar , K. Mölmer , T. Ala-Nissila

We study a coarse-graining map arising from incomplete and imperfect addressing of particles in a multipartite quantum system. In its simplest form, corresponding to a two-qubit state, the resulting channel produces a convex mixture of the…

Quantum Physics · Physics 2026-04-30 K. Uriostegui , C. Pineda , C. Chryssomalakos , V. Rascón Barajas , I. Vázquez Mota

We describe in detail the application of four qubit cluster states, built on the simultaneous entanglement of two photons in the degrees of freedom of polarization and linear momentum, for the realization of a complete set of basic one-way…

Quantum Physics · Physics 2008-11-05 Giuseppe Vallone , Enrico Pomarico , Francesco De Martini , Paolo Mataloni

The verification of quantum entanglement is essential for quality control in quantum communication. In this work, we propose an efficient protocol to directly verify the two-qubit entanglement of a known target state through a single…

Quantum Physics · Physics 2026-04-22 Ricardo Rodriguez , Nam Nguyen , Elizabeth Behrman , Andrew C. Y. Li , James Steck

Measurement-based quantum computation has revolutionized quantum information processing, and the physical systems with which it can be implemented. One simply needs the ability to prepare a particular state, known as the cluster state, and…

Quantum Physics · Physics 2008-02-15 Dimitris G. Angelakis , Alastair Kay

An error-corrected quantum processor will require millions of qubits, accentuating the advantage of nanoscale devices with small footprints, such as silicon quantum dots. However, as for every device with nanoscale dimensions, disorder at…

Quantum computers attract much attention as they promise to outperform their classical counterparts in solving certain type of problems. One of them with practical applications in quantum chemistry is simulation of complex quantum systems.…

Quantum Physics · Physics 2014-07-08 Libor Veis , Jiří Pittner

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

We propose a scheme to dissipatively produce steady-state entanglement in a two-qubit system, via an interaction with a bosonic mode. The system is driven into a stationary entangled state, while we compensate the mode dissipation by…

Quantum state preparation is an important subroutine in many quantum algorithms. The goal is to encode classical information directly to the quantum state so that it is possible to leverage quantum algorithms for data processing. However,…

Quantum Physics · Physics 2026-05-01 Oskari Kerppo , William Steadman , Ossi Niemimäki , Valtteri Lahtinen

We address the problem of optimal estimation of the relative phase for two-dimensional quantum systems in mixed states. In particular, we derive the optimal measurement procedures for an arbitrary number of qubits prepared in the same mixed…

Quantum Physics · Physics 2007-05-23 Giacomo Mauro D'Ariano , Chiara Macchiavello , Paolo Perinotti

The exact number of CNOT and single qubit gates needed to implement a Quantum Algorithm in a given architecture is one of the central problems of Quantum Computation. In this work we study the importance of concise realizations of Partially…

Quantum Physics · Physics 2020-07-21 Chandra Sekhar Mukherjee , Subhamoy Maitra , Vineet Gaurav , Dibyendu Roy