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Increasingly sophisticated programmable quantum simulators and quantum computers are opening unprecedented opportunities for exploring and exploiting the properties of highly entangled complex quantum systems. The complexity of large…

A general scheme is presented for controlling quantum systems using evolution driven by non-selective von Neumann measurements, with or without an additional tailored electromagnetic field. As an example, a 2-level quantum system controlled…

Quantum Physics · Physics 2007-05-23 Alexander Pechen , Nikolai Il'in , Feng Shuang , Herschel Rabitz

The ability to perform a universal set of quantum operations based solely on static resources and measurements presents us with a strikingly novel viewpoint for thinking about quantum computation and its powers. We consider the two major…

Quantum Physics · Physics 2007-05-23 Panos Aliferis , Debbie W. Leung

The measurement of a spin-$\half$ is modeled by coupling it to an apparatus, that consists of an Ising magnetic dot coupled to a phonon bath. Features of quantum measurements are derived from the dynamical solution of the measurement,…

Quantum Physics · Physics 2017-08-23 Armen E. Allahverdyan , Roger Balian , Theo M. Nieuwenhuizen

A single electron shared between two levels threaded by a magnetic flux is an irreducibly simple quantum system in which interference is predicted to occur. We demonstrate tuning of the tunnel coupling between two such electronic levels…

Mesoscale and Nanoscale Physics · Physics 2024-09-12 Christian G. Prosko , Ivan Kulesh , Michael Chan , Lin Han , Di Xiao , Candice Thomas , Michael J. Manfra , Srijit Goswami , Filip K. Malinowski

In textbooks, ideal quantum measurements are described in terms of the tested system only by the collapse postulate and Born's rule. This level of description offers a rather flexible position for the interpretation of quantum mechanics.…

Quantum Physics · Physics 2017-09-28 Theo M. Nieuwenhuizen , Marti Perarnau-Llobet , Roger Balian

Invasiveness of quantum measurements is a genuinely quantum mechanical feature that is not necessarily detrimental: Here we show how quantum measurements can be used to fuel a cooling engine. We illustrate quantum measurement cooling (QMC)…

Statistical Mechanics · Physics 2019-02-27 Lorenzo Buffoni , Andrea Solfanelli , Paola Verrucchi , Alessandro Cuccoli , Michele Campisi

The resources needed to conventionally characterize a quantum system are overwhelmingly large for high- dimensional systems. This obstacle may be overcome by abandoning traditional cornerstones of quantum measurement, such as general…

Quantum Physics · Physics 2016-05-17 Gregory A. Howland , Samuel H. Knarr , James Schneeloch , Daniel J. Lum , John C. Howell

The so-called quantum measurement problems are solved from a new perspective. One of the main observations is that the basic entities of our world are {\it particles}, elementary or composite. It follows that each elementary process, hence…

Quantum Physics · Physics 2023-02-20 Kenichi Konishi

Considering any Hamiltonian, any initial state, and measurements with a small number of possible outcomes compared to the dimension, we show that most measurements are already equilibrated. To investigate non-trivial equilibration we…

No quantum measurement can give full information on the state of a quantum system; hence any quantum feedback control problem is neccessarily one with partial observations, and can generally be converted into a completely observed control…

Mathematical Physics · Physics 2007-05-23 Mazyar Mirrahimi , Ramon van Handel

We present a generic model of (non-destructive) quantum measurement. Being formulated within reversible quantum mechanics, the model illustrates a mechanism of a measurement process --- a transition of the measured system to an eigenstate…

Quantum Physics · Physics 2017-11-06 Karl-Erik Eriksson , Martin Cederwall , Kristian Lindgren , Erik Sjöqvist

One of the main postulates of quantum mechanics is that measurements destroy quantum coherence (wave function collapse). Recently it was discovered that in a many-body system dilute local measurements still preserve some coherence across…

Quantum Physics · Physics 2025-05-13 Aleksei Khindanov , Igor L. Aleiner , Lara Faoro , Lev B. Ioffe

A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems…

The topic of measurement in relativistic quantum field theory is addressed in this article. Some of the long standing problems of this subject are highlighted, including the incompatibility of an instantaneous ``collapse of the…

Mathematical Physics · Physics 2024-11-21 Christopher J. Fewster , Rainer Verch

Quantum backflow refers to the counterintuitive fact that the probability can flow in the direction opposite to the momentum of a quantum particle. This phenomenon has been seen to be small and fragile for one-dimensional systems, in which…

Quantum Physics · Physics 2025-03-04 Maximilien Barbier , Arseni Goussev , Shashi C. L. Srivastava

While quantum speed-up in solving certain decision problems by a fault-tolerant universal quantum computer has been promised, a timely research interest includes how far one can reduce the resource requirement to demonstrate a provable…

Quantum Physics · Physics 2018-01-01 Jacob Miller , Stephen Sanders , Akimasa Miyake

It is widely known that `collapse of the wave function' on a quantum system A may be brought about by an interaction with another quantum system B. We will prove that this is not just a possible, but a necessary consequence of information…

Quantum Physics · Physics 2007-05-23 Bas Janssens

A new ontological view of the quantum measurement processes is given, which has bearings on many broader issues in the foundations of quantum mechanics as well. In this scenario a quantum measurement is a non-equilibrium phase transition in…

Quantum Physics · Physics 2007-05-23 Xiaolei Zhang

Measurements in quantum mechanics cannot perfectly distinguish all states and necessarily disturb the measured system. We present and analyse a proposal to demonstrate fundamental limits on quantum control of a single qubit arising from…