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Quantum weak measurements with states both pre- and postselected offer a window into a hitherto neglected sector of quantum mechanics. A class of such systems involves time dependent evolution with transitions possible. In this paper we…

Quantum Physics · Physics 2016-02-12 Sara Imari Walker , Paul C. W. Davies , Prasant Samantray , Yakir Aharonov

The aim of quantum system identification is to estimate the ingredients inside a black box, in which some quantum-mechanical unitary process takes place, by just looking at its input-output behavior. Here we establish a basic and general…

Quantum Physics · Physics 2012-02-27 Daniel Burgarth , Kazuya Yuasa

We introduce a quantum measurement process that is capable of characterizing an unknown state of a system almost without disturbing or collapsing it. The underlying idea is to extract information of a system from the thermodynamic…

Quantum Physics · Physics 2019-11-26 Mohit Lal Bera , Manabendra Nath Bera

We revisit the pointer-based measurement concept of von Neumann which allows us to model a quantum counterpart of the classical time-of-flight (ToF) momentum. Our approach is based on the Hamiltonian for a particle interacting with two…

Quantum Physics · Physics 2019-09-18 Fabio Di Pumpo , Matthias Freyberger

Every measurement on a quantum system causes a state change from the system state just before the measurement to the system state just after the measurement conditional upon the outcome of measurement. This paper determines all the possible…

Quantum Physics · Physics 2009-11-06 Masanao Ozawa

Estimation of quantum states and measurements is crucial for the implementation of quantum information protocols. The standard method for each is quantum tomography. However, quantum tomography suffers from systematic errors caused by…

Quantum Physics · Physics 2018-10-19 Adam C. Keith , Charles H. Baldwin , Scott Glancy , E. Knill

Quantum illumination consists in shining quantum light on a target region immersed in a bright thermal bath, with the aim of detecting the presence of a possible low-reflective object. If the signal is entangled with the receiver, then a…

Quantum Physics · Physics 2017-02-28 M. Sanz , U. Las Heras , J. J. Garcia-Ripoll , E. Solano , R. Di Candia

Measurements of single-mode phase observables are studied in the spirit of the quantum theory of measurement. We determine the minimal measurement models of phase observables and consider methods of measuring such observables by using a…

Quantum Physics · Physics 2015-06-15 Juha-Pekka Pellonpää , Jussi Schultz

We provide an affirmative answer to the question posed in the title. Our argument is based on a treatment of the Schroedinger dynamics of the composite of a quantum microsystem, S, and a macroscopic measuring apparatus, I, consisting of N…

Quantum Physics · Physics 2009-11-13 Geoffrey Sewell

Quantum measurement is a physical process. What physical resources and constraints does quantum mechanics require for measurement to produce the classical world we observe? Treating measurement as a fully unitary quantum process, our goal…

Quantum Physics · Physics 2025-12-09 Vishal Johnson , Ashmeet Singh , Reimar Leike , Philipp Frank , Torsten Enßlin

Quantum shape-phase transitions in finite nuclei are considered in the framework of the interacting boson model. Critical-point Hamiltonians for first- and second-order transitions are identified by resolving them into intrinsic and…

Nuclear Theory · Physics 2008-11-26 A. Leviatan

A communication protocol with non-zero quantum capacity is found when the two communicating parts are particle detector models in (3+1)-dimensional spacetime. In particular, as detectors, we consider two harmonic oscillators interacting…

General Relativity and Quantum Cosmology · Physics 2024-07-25 Alessio Lapponi , Jorma Louko , Stefano Mancini

Measurements of quantum systems can be used to generate classical data that is truly unpredictable for every observer. However, this true randomness needs to be discriminated from randomness due to ignorance or lack of control of the…

Quantum Physics · Physics 2017-06-14 Felix Bischof , Hermann Kampermann , Dagmar Bruß

The problem of the time of arrival of a quantum system in a specified state is considered in the framework of the repeated measurement protocol and in particular the limit of continuous measurements is discussed. It is shown that for a…

Quantum Physics · Physics 2021-04-07 Varun Dubey , Cedric Bernardin , Abhishek Dhar

Identifying the real and imaginary parts of wave functions with coordinates and momenta, quantum evolution may be mapped onto a classical Hamiltonian system. In addition to the symplectic form, quantum mechanics also has a positive-definite…

Quantum Physics · Physics 2009-11-07 R. Vilela Mendes , V. I. Man'ko

Quantum technology has been rapidly growing due to its potential revolutionary applications. In particular, superconducting qubits provide a strong light-matter interaction as required for quantum computation and in principle can be scaled…

Quantum Physics · Physics 2019-04-23 Mahdi Naghiloo

The term "measurement" in quantum theory (as well as in other physical theories) is ambiguous: It is used to describe both an experience - e.g., an observation in an experiment - and an interaction with the system under scrutiny. If doing…

Quantum Physics · Physics 2019-04-03 Arne Hansen , Stefan Wolf

Why do we need quantization to describe vision? What are the quadrature operators of the electromagnetic field? Is it possible to measure them? What are the characteristic functions useful for? In this brief tutorial we provide the…

Quantum Physics · Physics 2021-10-08 Stefano Olivares

A microscopic system under continuous observation exhibits at random times sudden jumps between its states. The detection of this essential quantum feature requires a quantum non-demolition (QND) measurement repeated many times during the…

Pointlike systems coupled to quantum fields are often employed as toy models for measurements in quantum field theory. In this paper, we identify the field observables recorded by such models. We show that in models that work in the strong…

Quantum Physics · Physics 2023-08-29 Maria Papageorgiou , Jose de Ramon , Charis Anastopoulos