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We address the problem of estimating pure qubit states with non-ideal (noisy) measurements in the multiple-copy scenario, where the data consists of a number N of identically prepared qubits. We show that the average fidelity of the…

Quantum Physics · Physics 2015-03-20 Bernat Gendra , Elio Ronco-Bonvehi , John Calsamiglia , Ramon Munoz-Tapia , Emilio Bagan

Adaptive measurements were recently shown to significantly improve the performance of quantum state tomography. Utilizing information about the system for the on-line choice of optimal measurements allows to reach the ultimate bounds of…

The phase of an optical field inside a linear amplifier is widely known to diffuse with a diffusion coefficient that is inversely proportional to the photon number. The same process occurs in lasers which limits its intrinsic linewidth and…

Quantum Physics · Physics 2019-11-06 A. Chia , M. Hajdusek , R. Fazio , L. C. Kwek , V. Vedral

Parametric amplifiers have allowed breakthroughs in ultrafast, strong-field, and high-energy density laser science and are an essential tool for extending the frequency range of powerful emerging diode-pumped solid-state laser technology.…

Entanglement plays an indispensable role in numerous quantum information and quantum computation tasks, underscoring the need for efficiently verifying entangled states. In recent years, quantum state verification has received increasing…

Quantum Physics · Physics 2025-12-15 Lan Zhang , Yinfei Li , Ye-Chao Liu , Jiangwei Shang

By harnessing the quantum states of light for illumination, precise phase and absorption estimations can be achieved with precision beyond the standard quantum limit. Despite their significance for precision measurements, quantum states are…

Quantum Physics · Physics 2018-08-15 Ming Li , Chang-Ling Zou , Di Liu , Guo-Ping Guo , Guang-Can Guo , Xi-Feng Ren

A recent theoretical proposal for teleamplification requires preparation of Fock states, programmable interferometers, and photon-number resolving detectors to herald the teleamplification of an input state. These enable teleportation and…

Quantum Physics · Physics 2023-12-08 Aaron Z. Goldberg , Khabat Heshami

We find that reinforcement exponentially reduces computation time of the quantum search problem from $\sqrt{D}$ to $\ln D$ in a $D$-dimensional system. Therefor, a reinforced quantum search is expected to exhibit an exponentially larger…

Quantum Physics · Physics 2026-04-07 Marjan Homayouni-Sangari , Abolfazl Ramezanpour

This paper focuses on the quantum amplitude estimation algorithm, which is a core subroutine in quantum computation for various applications. The conventional approach for amplitude estimation is to use the phase estimation algorithm, which…

Quantum Physics · Physics 2020-01-28 Yohichi Suzuki , Shumpei Uno , Rudy Raymond , Tomoki Tanaka , Tamiya Onodera , Naoki Yamamoto

In this paper, we present an algorithm for preparing quantum states of the form $\sum_{i=0}^{n-1} \alpha_i |i\rangle$, where the coefficients $\alpha_i$ are specified by a quantum oracle. Our method achieves this task twice as fast as the…

Quantum Physics · Physics 2025-06-17 Artem Chernikov , Karina Zakharova , Sergey Sysoev

When measuring phase of quantum states of light, the optimal single-shot measurement implements projection on the un-physical phase states. If we want to improve the precision further we need to accept a reduced probability of success,…

Quantum Physics · Physics 2015-06-16 Petr Marek

We show on theoretical grounds that, even in the presence of noise, probabilistic measurement strategies (which have a certain probability of failure or abstention) can provide, upon a heralded successful outcome, estimates with a precision…

Quantum Physics · Physics 2016-10-27 J. Calsamiglia , B. Gendra , R. Munoz-Tapia , E. Bagan

Amplification of signal intensity is essential for initiating physical processes, diagnostics, sensing, communications, and scientific measurement. During traditional amplification, the signal is amplified by multiplying the signal carriers…

Optics · Physics 2014-07-14 R. Maram , J. van Howe , M. Li , J. Azaña

We develop a framework for learning from noisy quantum experiments in which fault-tolerant devices access uncharacterized systems through noisy couplings. Introducing the complexity class $\textsf{NBQP}$ ("noisy BQP''), we model noisy…

Quantum Physics · Physics 2026-01-15 Jordan Cotler , Weiyuan Gong , Ishaan Kannan

We derive the ultimate bounds on the performance of nonlinear measurement schemes in the presence of noise. In particular, we investigate the precision of the second-order estimation scheme in the presence of the two most detrimental types…

Quantum Physics · Physics 2014-02-17 Marcin Zwierz , Howard M. Wiseman

Reducing noise in quantum systems is a major challenge towards the application of quantum technologies. Here, we propose and demonstrate a scheme to reduce noise using a quantum autoencoder with rigorous performance guarantees. The quantum…

The metrological ability of carefully designed probes can be spoilt by the presence of noisy processes occurring during their evolution. The noise is responsible for altering the evolution of the probes in such a way that bear little or no…

In this article, based on some simple and reasonable assumptions, we derive a Gaussian noise model for quantum amplitude estimation. We provide results from quantum amplitude estimation run on various IBM superconducting quantum computers…

Quantum Physics · Physics 2024-11-08 Steven Herbert , Ifan Williams , Roland Guichard , Darren Ng

Error filtration is a method for encoding the quantum state of a single particle into a higher dimensional Hilbert space in such a way that it becomes less sensitive to phase noise. We experimentally demonstrate this method by distributing…

Quantum Physics · Physics 2007-05-23 L. P. Lamoureux , E. Brainis , N. Cerf , Ph. Emplit , M. Haelterman , S. Massar

Amplifiers are crucial in every experiment carrying out a very sensitive measurement. However, they always degrade the information by adding noise. Quantum mechanics puts a limit on how small this degradation can be. Theoretically, the…

Mesoscale and Nanoscale Physics · Physics 2009-10-22 N. Bergeal , R. Vijay , V. E. Manucharyan , I. Siddiqi , R. J. Schoelkopf , S. M. Girvin , M. H. Devoret