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In this paper we consider feedback control algorithms for the rapid purification of a bipartite state consisting of two qubits, when the observer has access to only one of the qubits. We show 1) that the algorithm that maximizes the average…

Quantum Physics · Physics 2009-11-13 Charles D. Hill , J. F. Ralph

Purifying noisy entanglement is a protocol which can increase the entanglement of a mixed state (as a source)at expense of the entanglement of others(as an ancilla)by collective measurement. A protocol with which one can get a pure…

Quantum Physics · Physics 2009-11-07 Ping-Xing Chen , Lin-Mei Liang , Cheng-Zu Li , Ming-Qiu Huang

The reliable characterization of quantum states as well as any potential noise in various quantum systems is crucial for advancing quantum technologies. In this work we propose the concept of corrupted sensing quantum state tomography which…

Quantum Physics · Physics 2025-05-07 Mengru Ma , Jiangwei Shang

We present a general denoising algorithm for performing simultaneous tomography of quantum states and measurement noise. This algorithm allows us to fully characterize state preparation and measurement (SPAM) errors present in any quantum…

Given an ensemble of mixed qubit states, it is possible to increase the purity of the constituent states using a procedure known as state purification. The reverse operation, which we refer to as dilution, reduces the level of purity…

Quantum Physics · Physics 2015-03-18 Peter Bowles , Madalin Guta , Gerardo Adesso

Distillation, or purification, is central to the practical use of quantum resources in noisy settings often encountered in quantum communication and computation. Conventionally, distillation requires using some restricted 'free' operations…

Quantum Physics · Physics 2024-04-29 Xiao Yuan , Bartosz Regula , Ryuji Takagi , Mile Gu

Hyperentanglement is a promising resource in quantum information processing, especially for increasing the channel capacity of long-distance quantum communication. Hyperentanglement purification is an important method to obtain…

Quantum Physics · Physics 2015-06-22 Bao-Cang Ren , Fang-Fang Du , Fu-Guo Deng

Quantum networks, which integrate multiple quantum computers and the channels connecting them, are crucial for distributed quantum information processing but remain inherently susceptible to channel noise. Channel purification emerges as a…

We propose a quantum algorithm for the purification of a generic mixed state $\rho$ of a $n$-qudit system by using an ancillary $n$-qudit system. The algorithm is optimal in that (i) the number of ancillary qudits cannot be reduced, (ii)…

Quantum Physics · Physics 2009-05-04 Giuliano Benenti , Giuliano Strini

We study the use of entanglement purification for quantum communication over long distances. For distances much longer than the coherence length of a corresponding noisy quantum channel, the fidelity of transmission is usually so low that…

Quantum Physics · Physics 2008-12-18 W. Dür , H. - J. Briegel , J. I. Cirac , P. Zoller

We introduce a new decomposition of the multiqubit states of the form $\rho^{\otimes N}$ and employ it to construct the optimal single qubit purification procedure. The same decomposition allows us to study optimal quantum cloning and state…

Quantum Physics · Physics 2009-10-31 J. I. Cirac , A. K. Ekert , C. Macchiavello

We investigate efficient entanglement purification through double selection process. This method works with higher noise thresholds for the communication channels and local operations, and achieves higher fidelity of purified states.…

Quantum Physics · Physics 2015-05-13 Keisuke Fujii , Katsuji Yamamoto

Efficient verification of multipartite quantum states is crucial to many applications in quantum information processing. By virtue of Schmidt decomposition and mutually unbiased bases, here we propose a universal protocol to verify…

Quantum Physics · Physics 2026-03-04 Yunting Li , Huangjun Zhu

In tasks, where multipartite entanglement plays a central role, state purification is, due to inevitable noise, a crucial part of the procedure. We consider a scenario exploiting the multipartite entanglement in a straightforward…

Quantum Physics · Physics 2011-06-17 Marcus Huber , Martin Plesch

We introduce the concept of a physical process that purifies a mixed quantum state, taken from a set of states, and investigate the conditions under which such a purification map exists. Here, a purification of a mixed quantum state is a…

Quantum Physics · Physics 2007-05-23 M. Kleinmann , H. Kampermann , T. Meyer , D. Bruss

Degenerate quantum codes are codes that do not reveal the complete error syndrome. Their ability to conceal the complete error syndrome makes them powerful resources in certain quantum information processing tasks. In particular, the most…

Quantum Physics · Physics 2008-08-15 K. H. Ho , H. F. Chau

Quantum purity amplification (QPA) provides a novel approach to counteracting the pervasive noise that degrades quantum states. We present the optimal QPA protocol for general quantum systems and global noise, resolving a two-decade open…

Quantum Physics · Physics 2025-12-29 Zhaoyi Li , Honghao Fu , Takuya Isogawa , Caio Silva , Isaac Chuang

Quantum-limited amplifiers increase the amplitude of quantum signals at the price of introducing additional noise. Quantum purification protocols operate in the reverse way, by reducing the noise while attenuating the signal. Here we…

Quantum Physics · Physics 2017-04-12 Xiaobin Zhao , Giulio Chiribella

It is not a general opinion that that a quantum system could be purified into a target eigenstate via repeated measurements on a coupled qubit rather than direct transitions in the Hamiltonian. The projective measurement on the ancillary…

Quantum Physics · Physics 2023-10-30 Jia-shun Yan , Jun Jing

The reliable characterization of quantum states is a fundamental task in quantum information science. For this purpose, quantum state tomography provides a standard framework for reconstructing quantum states from measurement data, yet it…

Quantum Physics · Physics 2026-04-14 Yixuan Hu , Mengru Ma , Jiangwei Shang