We perform an analysis supplementing the metrology toolbox in the time-frequency domain. While the relevant time-frequency-based metrological protocols can be borrowed from the spatial domain, where they have recently been well developed, their ultimate practical usefulness is shown to be restricted by limits put on the bandwidth of both the signal and measurements, as well as by the finite measurement time. As we demonstrate for the well-known problem of multiparameter estimation for two incoherent, point-like sources, the impact of these experimental limitations on the optimal protocol's efficiency can be detrimental. Nonetheless, we propose necessary operational criteria for attainability of the quantum Cramér-Rao bound under the discussed restrictions.
Quantum optical metrology aims to identify ultimate sensitivity bounds for the estimation of parameters encoded into quantum states of the electromagnetic field. In many practical applications, including imaging, microscopy, and remote sensing, the parameter of interest is not only encoded in the quantum state of the field, but also in its spatio-temporal distribution, i.e. in its mode structure. In this mode-encoded parameter estimation setting, we derive an analytical expression for the quantum Fisher information valid for arbitrary multimode Gaussian fields. To illustrate the power of our a…
Quantum metrology enhances measurement precision by utilising the properties of quantum physics. In interferometry, this is typically achieved by evolving highly-entangled quantum states before performing single-shot measurements to reveal information about an unknown parameter. While this is often the optimum approach, implementation with all but the smallest states is still extremely challenging. An alternative approach is quantum jump metrology [L. A. Clark et al., Phys. Rev. A 99, 022102 (2019)] which deduces information by continuously monitoring an open quantum system, while inducing pha…
Identification of the optimal quantum metrological protocols in realistic many particle quantum models is in general a challenge that cannot be efficiently addressed by the state-of-the-art numerical and analytical methods. Here we provide a comprehensive framework exploiting matrix product operators (MPO) type tensor networks for quantum metrological problems. Thanks to the fact that the MPO formalism allows for an efficient description of short-range spatial and temporal noise correlations, the maximal achievable estimation precision in such models, as well as the optimal probe states in pre…
The large capacity and robustness of information encoding in the temporal mode of photons is important in quantum information processing, in which characterizing temporal quantum states with high usability and time resolution is essential. We propose and demonstrate a direct measurement method of temporal complex wavefunctions for weak light at a single-photon level with subpicosecond time resolution. Our direct measurement is realized by ultrafast metrology of the interference between the light under test and self-generated monochromatic reference light; no external reference light or complic…
Quantum-interference metrology of dissipative Kerr solitons
University of Electronic Science and Technology of China（电子科技大学）；Tianfu Jiangxi Laboratory（天府江西实验室）；Southwest Institute of Technical Physics（西南技术物理研究所）；Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences（中国科学院上海微系统信息技术研究所）；AMS；University of Science and Technology of China（中国科学技术大学）
CSS codes for Quantum Metrology with Discrete-time Error Correction
Institute of Data Science and Digital Technologies, Faculty of Mathematics and Informatics, Vilnius University（维尔纽斯大学数学与信息学院数据科学与数字技术研究所）；Institute for Theoretical Physics, Leibniz University Hannover（汉诺威莱布尼茨大学理论物理研究所）
We consider application of a temporal imaging system, based on the sum-frequency generation, to a nonclassical, in particular, squeezed optical temporal waveform. We analyze the restrictions on the pump and the phase matching condition in the summing crystal, necessary for preserving the quantum features of the initial waveform. We show that modification of the notion of the field of view in the quantum case is necessary, and that the quantum field of view is much narrower than the classical one for the same temporal imaging system. These results are important for temporal stretching and compr…
Temporal-spectral modes of light provide a fundamental window into the nature of atomic and molecular systems and offer robust means for information encoding. Methods to precisely characterize the temporal-spectral state of light at the single-photon level thus play a central role in understanding quantum emitters and are a key requirement for quantum technologies that harness single-photon states. Here we demonstrate an optical reference-free method, which melds techniques from ultrafast metrology and single-photon spectral detection, to characterize the temporal-spectral state of single phot…
Measuring the spectral properties of an optical frequency comb is among the most fundamental tasks of precision metrology. In contrast to general single-parameter measurement schemes, we demonstrate here single shot multiparameter estimation at and beyond the standard quantum limit. The mean energy and the central frequency of ultrafast pulses are simultaneously determined with a multi-pixel-spectrally-resolved (MPSR) apparatus, without changing the photonics architecture. Moreover, using a quantum frequency comb that consists of multiple squeezed states in a family of Hermite-Gaussian spectra…
Stabilizing temporal quantum-enhanced sensitivity via sub-optimal measurements
University of Electronic Science and Technology of China（电子科技大学）；Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China（电子科技大学前沿科学与工程学院）；Key Laboratory of Quantum Physics and Photonic Quantum Information, Ministry of Education, University of Electronic Science and Technology of China（教育部量子物理与光子量子信息重点实验室，电子科技大学）
Conventional optical synthesis, the manipulation of the phase and amplitude of spectral components to produce an optical pulse in different temporal modes, is revolutionizing ultrafast optical science and metrology. These technologies rely on the Fourier transform of light fields between time and frequency domains in one-dimensional space. However, within this treatment it is impossible to incorporate the quantum correlation among photons. Here we expand the Fourier synthesis into high dimensional space to deal with the quantum correlation, and carry out an experimental demonstration by manipu…
Chaos-Mediated Quantum State Discrimination Near Unit Fidelity
Indian Institute of Science Education and Research Kolkata（印度科学教育研究所加尔各答分校）；Ben-Gurion University of the Negev（内盖夫本古里安大学）；IU Indianapolis（印第安纳大学-普渡大学印第安纳波利斯联合分校）
Single-shot pulse retrieval of femtosecond bright squeezed vacuum
Technion – Israel Institute of Technology（以色列理工学院）；Solid State Institute（固态研究所）；Helen Diller Quantum Center（海伦·迪勒量子中心）；The Russell Berrie Nanotechnology Institute（罗素·贝里纳米技术研究所）；Max Planck Institute for the Science of Light（马克斯·普朗克光科学研究所）；Friedrich–Alexander Universität Erlangen–Nürnberg（埃尔朗根-纽伦堡弗里德里希-亚历山大大学）
A promising result from optical quantum metrology is the ability to achieve sub-shot-noise performance in transmission or absorption measurements. This is due to the significantly lower uncertainty in light intensity of quantum beams with respect to their classical counterparts. In this work, we simulate the outcome of an experiment that uses a multiplexed single-photon source based on pair generation by continuous spontaneous parametric down conversion (SPDC) followed by a time multiplexing set-up with a binary temporal division strategy, considering several types of experimental losses. With…
Time correlations from steady-state expectation values
Freie Universität Berlin（柏林自由大学）；INFN Sez. Pavia（意大利国家核物理研究所帕维亚分部）；Institute for Complex Systems, National Research Council (ISC-CNR)（国家研究委员会复杂系统研究所）；Physics Department, Sapienza University（罗马第一大学物理系）；Dip. Fisica, University of Pavia（帕维亚大学物理系）；Department of Information and Communications Engineering, Aalto University（阿尔托大学信息与通信工程系）
