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Quantum de Finetti theorems are a useful tool in the study of correlations in quantum multipartite states. In this paper we prove two new quantum de Finetti theorems, both showing that under tests formed by local measurements one can get a…

Quantum Physics · Physics 2017-05-16 Fernando G. S. L. Brandao , Aram W. Harrow

Qudits hold great promise for efficient quantum computation and the simulation of high-dimensional quantum systems. Utilizing a local Hilbert space of dimension d > 2 is known to speed up certain quantum algorithms relative to their qubit…

Quantum Physics · Physics 2025-06-23 Elizabeth Champion , Zihao Wang , Rayleigh Parker , Machiel Blok

Bit commitment is a fundamental cryptographic task that guarantees a secure commitment between two mutually mistrustful parties and is a building block for many cryptographic primitives, including coin tossing, zero-knowledge proofs,…

The fidelity of quantum cloning is very often limited by the accompanying unwanted transitions. We show how the fidelity can be improved by using a coherent field to cycle away the unwanted transitions. We demonstrate this explicitly in the…

Quantum Physics · Physics 2009-11-06 Shubhrangshu Dasgupta , G. S. Agarwal

Quantum systems can be used as probes in the context of metrology for enhanced parameter estimation. In particular, the delicacy of critical systems to perturbations can make them ideal sensors. Arguably the simplest realistic probe system…

Quantum Physics · Physics 2024-07-04 George Mihailescu , Abolfazl Bayat , Steve Campbell , Andrew K. Mitchell

We study the robustness of the evolution of a quantum system against small uncontrolled variations in parameters in the Hamiltonian. We show that the fidelity susceptibility, which quantifies the perturbative error to leading order, can be…

Quantum Physics · Physics 2024-05-09 Pablo M. Poggi , Gabriele De Chiara , Steve Campbell , Anthony Kiely

Quantum metrology plays a fundamental role in many scientific areas. However, the complexity of engineering entangled probes and the external noise raise technological barriers for realizing the expected precision of the to-be-estimated…

Quantum Physics · Physics 2021-01-21 Xiaodong Yang , Xi Chen , Jun Li , Xinhua Peng , Raymond Laflamme

We show that a family of quantum authentication protocols introduced in [Barnum et al., FOCS 2002] can be used to construct a secure quantum channel and additionally recycle all of the secret key if the message is successfully…

Quantum Physics · Physics 2017-04-24 Christopher Portmann

A central problem in quantum computational complexity is how to prevent entanglement-assisted cheating in multi-prover interactive proof systems. It is well-known that the standard oracularization technique completely fails in some proof…

Quantum Physics · Physics 2008-10-06 Tsuyoshi Ito , Hirotada Kobayashi , Keiji Matsumoto

We give a natural problem over input quantum oracles $U$ which cannot be solved with exponentially many black-box queries to $U$ and $U^\dagger$, but which can be solved with constant many queries to $U$ and $U^*$, or $U$ and…

Quantum Physics · Physics 2026-05-11 Ewin Tang , John Wright , Mark Zhandry

We propose a computational protocol for quantum simulations of Fermionic Hamiltonians on a quantum computer, enabling calculations which were previously not feasible with conventional encoding and ansatses of variational quantum…

Quantum Physics · Physics 2023-03-15 Benchen Huang , Nan Sheng , Marco Govoni , Giulia Galli

We have taken significant steps towards the realization of a practical quantum computer: using nuclear spins and magnetic resonance techniques at room temperature, we provided proof of principle of quantum computing in a series of…

Quantum Physics · Physics 2009-09-29 Lieven M. K. Vandersypen

We give a security proof of the `Round Robin Differential Phase Shift' Quantum Key Distribution scheme, and we give a tight bound on the required amount of privacy amplification. Our proof consists of the following steps. We construct an…

Quantum Physics · Physics 2018-02-09 Daan Leermakers , Boris Skoric

Computing Fourier transforms of k-sparse signals, where only k of N frequencies are non-zero, is fundamental in compressed sensing, radar, and medical imaging. While the Fast Fourier Transform (FFT) evaluates all N frequencies in $O(N \log…

Signal Processing · Electrical Eng. & Systems 2026-04-22 Aaron R. Flouro , Shawn P. Chadwick

We devise a simple modification that essentially doubles the efficiency of the BB84 quantum key distribution scheme proposed by Bennett and Brassard. We also prove the security of our modified scheme against the most general eavesdropping…

Quantum Physics · Physics 2016-09-08 Hoi-Kwong Lo , H. F. Chau , M. Ardehali

A simple and flexible scheme for high-dimensional linear quantum operations on optical transverse spatial modes is demonstrated. The quantum Fourier transformation (QFT) and quantum state tomography (QST) via symmetric informationally…

Quantum Physics · Physics 2020-08-19 Shikang Li , Shan Zhang Xue Feng , Stephen M. Barnett , Wei Zhang , Kaiyu Cui , Fang Liu , Yidong Huang

Quantum computing has advanced rapidly in recent years and has shown advantages in a variety of domains. In this paper, we investigate its potential for discrete simulation optimization in the fixed-confidence setting, a fundamental problem…

Quantum Physics · Physics 2026-04-30 Mingjie Hu , Jian-qiang Hu , Enlu Zhou

Developing optimal strategies to calibrate quantum processors for high-fidelity operation is one of the outstanding challenges in quantum computing today. Here, we demonstrate multiple examples of high-fidelity operations achieved using a…

Classical forgery attacks against Offset Two-round (OTR) structures require some harsh conditions, such as some plaintext and ciphertext pairs need to be known, and the success probability is not too high. To solve these problems, a quantum…

Quantum Physics · Physics 2024-05-14 Wenjie Liu , Mengting Wang , Zixian Li

In this article, we discuss the optimality of basis transformations as a security measure for quantum key distribution protocols based on entanglement swapping. To estimate the security, we focus on the information an adversary obtains on…

Quantum Physics · Physics 2013-07-23 Stefan Schauer , Martin Suda