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Weak measurements in combination with post-selection can give rise to a striking amplification effect (related to a large "weak value"). We show that this effect can be understood by viewing the initial state of the pointer as the ground…

Quantum Physics · Physics 2015-05-20 Christoph Simon , Eugene S. Polzik

The notion of weak measurement provides a formalism for extracting information from a quantum system in the limit of vanishing disturbance to its state. Here we extend this formalism to the measurement of sequences of observables. When…

Quantum Physics · Physics 2009-11-13 Graeme Mitchison , Richard Jozsa , Sandu Popescu

The measurement of quantum states is one of the most important problems in quantum mechanics. We introduce a quantum state tomography technique in which the state of a qubit is reconstructed, while the qubit remains undetected. The key…

We demonstrate an implementation of unambiguous state discrimination of two equally probable single-qubit states via a one-dimensional photonic quantum walk experimentally. Furthermore we experimentally realize a quantum walk algorithm for…

Quantum Physics · Physics 2014-10-10 Zhihao Bian , Rong Zhang , Hao Qin , Xiang Zhan , Jian Li , Peng Xue

What knowledge can be obtained from the record of a continuous measurement about the quantum state the measured system was in at the beginning of the measurement? The task of quantum state retrodiction, the inverse of the more common state…

Quantum Physics · Physics 2024-01-30 Jonas Lammers , Klemens Hammerer

Tomography of a quantum state is usually based on positive operator-valued measure (POVM) and on their experimental statistics. Among the available reconstructions, the maximum-likelihood (MaxLike) technique is an efficient one. We propose…

In quantum mechanics the statistics of the outcomes of a measuring apparatus is described by a positive operator valued measure (POVM). A quantum channel transforms POVM's into POVM's, generally irreversibly, thus loosing some of the…

Quantum Physics · Physics 2007-05-23 F. Buscemi , G. M. D'Ariano , M. Keyl , P. Perinotti , R. Werner

Current quantum computer technology is sufficient to realize weak measurements and the corresponding concept of weak values. We demonstrate how the weak value anomaly can be tested, along with consistency and simultaneity of weak values,…

Quantum Physics · Physics 2010-02-20 Todd A. Brun , Lajos Diosi , Walter T. Strunz

Understanding the energy cost of quantum measurement process and its connection to the measurement performance faces the challenge of modeling the objectification process. The latter, turns the measurement result into an objective fact,…

Quantum Physics · Physics 2025-12-19 Lorena Ballesteros Ferraz , Cyril Elouard

In this letter, we present a new procedure to determine completely the complex modular values of arbitrary observables of pre- and post-selected ensembles, which works experimentally for all measurement strengths and all post-selected…

Quantum Physics · Physics 2016-04-29 Mirko Cormann , Mathilde Remy , Branko Kolaric , Yves Caudano

Given an ensemble of qubits, which we are told consists of a mixture of two pure states, one with probability $\eta_{0}$ and one with probability $\eta_{1}$, we want to find a POVM that will discriminate between the two states by measuring…

Quantum Physics · Physics 2020-11-11 Mark Hillery

Traditional uncertainty relations dictate a minimal amount of noise in incompatible projective quantum measurements. However, not all measurements are projective. Weak measurements are minimally invasive methods for obtaining partial state…

Quantum Physics · Physics 2021-03-15 Jonathan T. Monroe , Nicole Yunger Halpern , Taeho Lee , Kater W. Murch

Many applications of quantum optics demand delicate quantum properties of light carefully tailored to accomplish a specific task. To this end, numerical simulations of quantum light sources are vital for designing, characterizing, and…

Quantum Physics · Physics 2023-10-09 Stephen C. Wein

We propose an estimation method for quantum measurement tomography (QMT) based on semidefinite programming (SDP), and discuss how it may be employed to detect experimental imperfections, such as shot noise and/or faulty preparation of the…

We discuss a possibility to build a programmable quantum measurement device (a "quantum multimeter"). That is, a device that would be able to perform various desired generalized, positive operator value measure (POVM) measurements depending…

Quantum Physics · Physics 2013-05-29 Miloslav Dusek , Vladimir Buzek

We propose a scheme to implement general quantum measurements, also known as Positive Operator Valued Measures (POVMs) in dimension $d$ using only classical resources and a single ancillary qubit. Our method is based on the probabilistic…

Quantum Physics · Physics 2023-03-14 Tanmay Singal , Filip B. Maciejewski , Michał Oszmaniec

Statistical ensemble formalism of Kim, Mandel and Wolf (J. Opt. Soc. Am. A 4, 433 (1987)) offers a realistic model for characterizing the effect of stochastic non-image forming optical media on the state of polarization of transmittedlight.…

Optics · Physics 2007-06-26 Sudha , A. V. Gopala Rao , A. R. Usha Devi , A. K. Rajagopal

We present a two-step protocol for quantum measurement tomography that is light on classical co-processing cost and still achieves optimal sample complexity in the system dimension. Given measurement data from a known probe state ensemble,…

Quantum Physics · Physics 2025-12-01 Leonardo Zambrano , Sergi Ramos-Calderer , Richard Kueng

Conventional absorption spectroscopy relies on coherent laser sources, and in turn suffers from the inherent limitation of shot noise, especially in estimating weak absorption. Here we propose a measurement strategy with correlated photons…

Quantum Physics · Physics 2025-04-17 Zhucheng Zhang , Xue Zhang , Jing Liu , Hui Dong

We present an effective measurement scheme for the solid-state qubits that does {\bf not} introduce extra decoherence to the qubits until the measurement is switched on by a resonant pulse. The resonant pulse then maximally entangles the…

Quantum Physics · Physics 2011-07-26 L. Tian , S. Lloyd , T. P. Orlando