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Regularisation theory in Banach spaces, and non--norm-squared regularisation even in finite dimensions, generally relies upon Bregman divergences to replace norm convergence. This is comparable to the extension of first-order optimisation…

Optimization and Control · Mathematics 2021-03-19 Tuomo Valkonen

We obtain the optimal scheme for estimating unknown qubit mixed states when an arbitrary number N of identically prepared copies is available. We discuss the case of states in the whole Bloch sphere as well as the restricted situation where…

Quantum Physics · Physics 2009-11-11 E. Bagan , M. A. Ballester , R. D. Gill , A. Monras , R. Munoz-Tapia

Uncertainty propagation and filtering can be interpreted as gradient flows with respect to suitable metrics in the infinite dimensional manifold of probability density functions. Such a viewpoint has been put forth in recent literature, and…

Optimization and Control · Mathematics 2017-10-31 Abhishek Halder , Tryphon T. Georgiou

Many problems in nonlinear and statistical physics are formulated through represented flows, including physical-space vector fields, phase-space drift fields, and truncated renormalization-group beta functions. We introduce a complementary…

Statistical Mechanics · Physics 2026-05-27 Amir Jafari

We propose techniques for implementing two different rapid state purification schemes, within the constraints present in a superconducting charge qubit system. Both schemes use a continuous measurement of charge (z) measurements, and seek…

Quantum Physics · Physics 2007-05-23 E. J. Griffith , C. D. Hill , J. F. Ralph , H. M. Wiseman , Kurt Jacobs

Entanglement purification is a crucial technique for promising the effective entanglement channel in noisy large-scale quantum networks, yet complicated in designing protocols in multi-degree of freedom (DoF). To execute the above tasks…

Quantum Physics · Physics 2023-10-20 Hao Zhang , Xusheng Xu , Chen Zhang , Man-Hong Yung , Tao Huang , Yunjie Liu

We present a depth-aware optimization framework for quantum circuit compilation that unifies provable optimality with scalable heuristics. For exact synthesis of a target unitary, we formulate a mixed-integer linear program (MILP) that…

Quantum Physics · Physics 2025-10-02 Harsha Nagarajan , Zsolt Szabó

In standard optical tomographic methods, the off-diagonal elements of a density matrix $\rho$ are measured indirectly. Thus, the reconstruction of $\rho$, even if it is based on linear inversion, typically magnifies small errors in the…

Quantum Physics · Physics 2016-07-19 Karol Bartkiewicz , Antonín Černoch , Karel Lemr , Adam Miranowicz

Conventional quantum computing entails a geometry based on the description of an n-qubit state using 2^{n} infinite precision complex numbers denoting a vector in a Hilbert space. Such numbers are in general uncomputable using any…

Quantum Physics · Physics 2015-06-05 Andrew J. Hanson , Gerardo Ortiz , Amr Sabry , Yu-Tsung Tai

We introduce a class of quantum channels with correlations acting on pairs of qubits, where the correlation takes the form of a shift operator onto a maximally entangled state. We optimise the output purity and show that below a certain…

Quantum Physics · Physics 2008-05-19 Filippo Caruso , Vittorio Giovannetti , Chiara Macchiavello , Mary Beth Ruskai

We posit a geometrical description of the entanglement of purification for subregions in a holographic CFT. The bulk description naturally generalizes the two-party case and leads to interesting inequalities among multi-party entanglements…

High Energy Physics - Theory · Physics 2019-02-27 Ning Bao , Aidan Chatwin-Davies , Grant N. Remmen

In this paper, we propose an unfitted Nitsche's method to compute the band structures of phononic crystal with impurities of general geometry. The proposed method does not require the background mesh to fit the interfaces of impurities, and…

Numerical Analysis · Mathematics 2021-04-07 Hailong Guo , Xu Yang , Yi Zhu

In recent years, there is a growing interest in using quantum computers for solving combinatorial optimization problems. In this work, we developed a generic, machine learning-based framework for mapping continuous-space inverse design…

We investigate entanglement in two-qubit systems using a geometric representation based on the minimum of essential parameters. The latter is achieved by requiring subsystems with the same entropy, regardless of whether the state of the…

Quantum Physics · Physics 2024-12-24 Salvio Luna-Hernandez , Claudia Quintana , Oscar Rosas-Ortiz

The quantum phase diagram for a finite $3$-level system in the $\Lambda$ configuration, interacting with a two-mode electromagnetic field in a cavity, is determined by means of information measures such as fidelity, fidelity susceptibility…

Quantum Physics · Physics 2023-02-21 O. Castaños , S. Cordero , R. López-Peña , E. Nahmad-Achar

Quantum purity amplification (QPA) is the task of coherently transforming $n$ copies of a mixed state into high-fidelity copies of a chosen eigenstate. We solve QPA in the general setting of $n$ input copies, $m$ output copies, arbitrary…

Quantum Physics · Physics 2026-05-22 Zhaoyi Li , Elias Theil , Aram W. Harrow , Isaac Chuang

$\mathcal{PT}$-symmetric systems have garnered significant attention due to their unconventional properties. Despite the growing interest, there remains an ongoing debate about whether these systems outperform their Hermitian counterparts…

Quantum Physics · Physics 2025-04-23 Yaroslav Balytskyi , Yevgen Kotukh , Gennady Khalimov , Sang-Yoon Chang

Diffusion Purification, purifying noised images with diffusion models, has been widely used for enhancing certified robustness via randomized smoothing. However, existing frameworks often grapple with the balance between efficiency and…

Computer Vision and Pattern Recognition · Computer Science 2024-07-02 Yiquan Li , Zhongzhu Chen , Kun Jin , Jiongxiao Wang , Bo Li , Chaowei Xiao

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

We exploit insights into the geometry of bosonic and fermionic Gaussian states to develop an efficient local optimization algorithm to extremize arbitrary functions on these families of states. The method is based on notions of gradient…

Quantum Physics · Physics 2021-03-17 Bennet Windt , Alexander Jahn , Jens Eisert , Lucas Hackl
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