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Sharing entanglement across quantum interconnects is fundamental for quantum information processing. We discuss a practical setting where this interconnect, modeled by a quantum channel, is used once with the aim of sharing high fidelity…

Quantum Physics · Physics 2023-10-09 Vikesh Siddhu , John Smolin

A scheme for optimal Gaussian cloning of optical coherent states is proposed and experimentally demonstrated. Its optical realization is based entirely on simple linear optical elements and homodyne detection. The optimality of the…

Quantum Physics · Physics 2009-11-11 Ulrik L. Andersen , Vincent Josse , Gerd Leuchs

Optimizing objective functions stands to benefit significantly from leveraging quantum computers, promising enhanced solution quality across various application domains in the future. However, harnessing the potential of quantum solvers…

Quantum Physics · Physics 2025-10-15 Deborah Volpe , Nils Quetschlich , Mariagrazia Graziano , Giovanna Turvani , Robert Wille

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

The impossibility of perfectly copying (or cloning) an arbitrary quantum state is one of the basic rules governing the physics of quantum systems. The processes that perform the optimal approximate cloning have been found in many cases.…

Quantum Physics · Physics 2009-11-11 Valerio Scarani , Sofyan Iblisdir , Nicolas Gisin , Antonio Acin

The accuracies of modern quantum logic clocks have surpassed those of standard atomic fountain clocks. These clocks also provide a greater degree of control, because before and after clock queries, we are able to apply chosen unitary…

Quantum Physics · Physics 2011-07-28 Michael Mullan , Emanuel Knill

Cryptanalysis on standard quantum cryptographic systems generally involves finding optimal adversarial attack strategies on the underlying protocols. The core principle of modelling quantum attacks in many cases reduces to the adversary's…

Quantum Physics · Physics 2022-04-14 Brian Coyle , Mina Doosti , Elham Kashefi , Niraj Kumar

Encoding combinatorial optimization problems into physically meaningful Hamiltonians with tractable energy landscapes forms the foundation of quantum optimization. Numerous works have studied such efficient encodings for the class of…

Quantum Physics · Physics 2026-02-12 Sebastian Egginger , Kristina Kirova , Sonja Bruckner , Stefan Hillmich , Richard Kueng

One of the most basic computational problems is the task of finding a desired item in an ordered list of N items. While the best classical algorithm for this problem uses log_2 N queries to the list, a quantum computer can solve the problem…

Quantum Physics · Physics 2007-05-23 Andrew M. Childs , Andrew J. Landahl , Pablo A. Parrilo

In this paper we give a simple sequence of necessary and sufficient finite dimensional conditions for a positive map between certain subspaces of bounded linear operators on separable Hilbert spaces to be completely positive. These…

Operator Algebras · Mathematics 2018-07-09 Shmuel Friedland

Semidefinite relaxations of polynomial optimization have become a central tool for addressing the non-convex optimization problems over non-commutative operators that are ubiquitous in quantum information theory and, more in general,…

Quantum Physics · Physics 2025-12-22 Younes Naceur , Jie Wang , Victor Magron , Antonio Acín

With the applications of quantum computing becoming more and more widespread, finding ways that allow end users without experience in the field to apply quantum computers to solve their individual problems is becoming a crucial task.…

Quantum Physics · Physics 2024-04-18 Damian Rovara , Nils Quetschlich , Robert Wille

In a topological quantum computer, universality is achieved by braiding and quantum information is natively protected from small local errors. We address the problem of compiling single-qubit quantum operations into braid representations…

Quantum Physics · Physics 2015-06-17 Vadym Kliuchnikov , Alex Bocharov , Krysta M. Svore

Despite the numerous uses of semidefinite programming (SDP) and its universal solvability via interior point methods (IPMs), it is rarely applied to practical large-scale problems. This mainly owes to the computational cost of IPMs that…

Optimization and Control · Mathematics 2024-03-19 Yifan Ran , Stefan Vlaski , Wei Dai

In this manuscript, we investigate optimal control problems which arise in connection with manipulation of dissipative quantum dynamics. These problems motivate the study of a class of dissipative bilinear control systems. For these systems…

Optimization and Control · Mathematics 2014-01-17 Dionisis Stefanatos , Navin Khaneja

We formalize the correspondence between quantum states and quantum operations isometrically, and harness its consequences. This correspondence was already implicit in the various proofs of the operator sum representation of Completely…

Quantum Physics · Physics 2009-11-10 Pablo Arrighi , Christophe Patricot

We develop a framework of "semi-automatic differentiation" that combines existing gradient-based methods of quantum optimal control with automatic differentiation. The approach allows to optimize practically any computable functional and is…

Quantum Physics · Physics 2022-12-13 Michael H. Goerz , Sebastián C. Carrasco , Vladimir S. Malinovsky

Identifying clusters of similar objects in data plays a significant role in a wide range of applications. As a model problem for clustering, we consider the densest k-disjoint-clique problem, whose goal is to identify the collection of k…

Optimization and Control · Mathematics 2015-03-20 Brendan P. W. Ames

A semidefinite program (SDP) is a particular kind of convex optimization problem with applications in operations research, combinatorial optimization, quantum information science, and beyond. In this work, we propose variational quantum…

Quantum Physics · Physics 2024-06-19 Dhrumil Patel , Patrick J. Coles , Mark M. Wilde

While quantum weight enumerators establish some of the best upper bounds on the minimum distance of quantum error-correcting codes, these bounds are not optimized to quantify the performance of quantum codes under the effect of arbitrary…

Quantum Physics · Physics 2022-07-20 Yingkai Ouyang , Ching-Yi Lai