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Any repeated use of a fixed experimental instrument is subject to memory effects. We design an estimation method uncovering the details of the underlying interaction between the system and the internal memory without having any experimental…

Quantum Physics · Physics 2015-10-21 Tomas Rybar , Mario Ziman

Ensuring the correct functioning of quantum error correction (QEC) circuits is crucial to achieve fault tolerance in realistic quantum processors subjected to noise. The first checkpoint for a fully operational QEC circuit is to create…

Quantum Physics · Physics 2021-04-14 Andrea Rodriguez-Blanco , Alejandro Bermudez , Markus Müller , Farid Shahandeh

We present a general model for quantum channels with memory, and show that it is sufficiently general to encompass all causal automata: any quantum process in which outputs up to some time t do not depend on inputs at times t' > t can be…

Quantum Physics · Physics 2009-11-11 Dennis Kretschmann , Reinhard F. Werner

A protocol with the potential of beating the existing distance records for conventional quantum key distribution (QKD) systems is proposed. It borrows ideas from quantum repeaters by using memories in the middle of the link, and that of…

Quantum Physics · Physics 2014-09-02 Christiana Panayi , Mohsen Razavi , Xiongfeng Ma , Norbert Lütkenhaus

The dynamics of open quantum system are often modeled by non-Markovian processes that account for memory effects arising from interactions with the environment. It is well-known that the memory provided by the environment can be classical…

Quantum Physics · Physics 2025-10-22 Charlotte Bäcker , Konstantin Beyer , Walter T. Strunz

Quantum metric learning enhances machine learning by mapping classical data to a quantum Hilbert space with maximal separation between classes. However, on current NISQ hardware, this mapping process itself is prone to errors and could be…

Quantum Physics · Physics 2026-03-31 Ahmed Shokry , Movahhed Sadeghi , Mahmut Kandemir

Continuous-variable (CV) measurement-device-independent (MDI) quantum key distribution (QKD) is immune to imperfect detection devices, which can eliminate all kinds of attacks on practical detectors. Here we first propose a CV-MDI QKD…

Quantum Physics · Physics 2021-08-13 Dongyun Bai , Peng Huang , Yiqun Zhu , Hongxin Ma , Tailong Xiao , Tao Wang , Guihua Zeng

Continuous-variable (CV) quantum computing has shown great potential for building neural network models. These neural networks can have different levels of quantum-classical hybridization depending on the complexity of the problem. Previous…

Quantum Physics · Physics 2023-06-08 Shikha Bangar , Leanto Sunny , Kubra Yeter-Aydeniz , George Siopsis

The protocol of the teleportation of an arbitrary unknown one-qubit state is investigated when the quantum channel is subject to the decoherence from the non-Markovian environments with the memory effects. The quality of the teleportation…

Quantum Physics · Physics 2012-08-09 Xiang Hao , Shiqun Zhu

Suppose we have an unknown multipartite quantum state, how can we experimentally find out whether it is genuine multipartite entangled or not? Recall that even for a bipartite quantum state whose density matrix is known, it is already…

Quantum Physics · Physics 2022-11-16 Zhenyu Chen , Xiaodie Lin , Zhaohui Wei

Digital signatures ensure the integrity of a classical message and the authenticity of its sender. Despite their far-reaching use in modern communication, currently used signature schemes rely on computational assumptions and will be…

Quantum Physics · Physics 2022-12-26 Matthew Thornton , Hannah Scott , Callum Croal , Natalia Korolkova

Learning unknown processes affecting a quantum system reveals underlying physical mechanisms and enables suppression, mitigation, and correction of unwanted effects. Describing a general quantum process requires an exponentially large…

We consider quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance for channels with…

Quantum Physics · Physics 2009-12-21 Giulio Chiribella , Giacomo M. D'Ariano , Paolo Perinotti

Using the axiomatic definition of the coherence measure, such as the $l_{1}$ norm and the relative entropy, we study the phenomena of two-qubit system quantum coherence through quantum channels where successive uses of the channels are…

Quantum Physics · Physics 2016-12-30 You-neng Guo , Ke Zeng , Qing-long Tian , Zheng-da Li

Entanglement is a fundamental aspect of quantum physics, both conceptually and for its many applications. Classifying an arbitrary multipartite state as entangled or separable -- a task referred to as the separability problem -- poses a…

Quantum transmission links are central elements in essentially all protocols involving the exchange of quantum messages. Emerging progress in quantum technologies involving such links needs to be accompanied by appropriate certification…

Memory-assisted measurement-device-independent quantum key distribution (MA-MDI-QKD) has recently been proposed as a possible intermediate step towards the realization of quantum repeaters. Despite its relaxing some of the requirements on…

Quantum Physics · Physics 2017-03-31 Nicoló Lo Piparo , Mohsen Razavi , William J. Munro

This thesis initiates the study of cryptographic protocols in the bounded-quantum-storage model. On the practical side, simple protocols for Rabin Oblivious Transfer, 1-2 Oblivious Transfer and Bit Commitment are presented. No quantum…

Quantum Physics · Physics 2007-09-04 Christian Schaffner

An optical procedure in the context of continuous variables to verify bipartite entanglement without destroying both systems and their entanglement is proposed. To perform the nondestructive verification of entanglement, the method relies…

Quantum Physics · Physics 2016-07-06 Alencar J. de Faria

There is a big gap between theory and practice in quantum key distribution (QKD) because real devices do not satisfy the assumptions required by the security proofs. Here, we close this gap by introducing a simple and practical…

Quantum Physics · Physics 2021-03-31 Álvaro Navarrete , Margarida Pereira , Marcos Curty , Kiyoshi Tamaki