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The evolution of a quantum system comprises two fundamental processes--continuous unitary dynamics and stochastic measurement-induced jumps. The latter are often viewed as a source of decoherence. Can two histories of such an evolution,…

Quantum Physics · Physics 2026-05-25 Parveen Kumar , Igor V. Gornyi , Yuval Gefen

Analog and digital quantum simulators can efficiently simulate quantum many-body systems that appear in natural phenomena. However, experimental limitations of near-term devices still make it challenging to perform the entire process of…

Quantum Physics · Physics 2024-09-13 Hideaki Hakoshima , Suguru Endo , Kaoru Yamamoto , Yuichiro Matsuzaki , Nobuyuki Yoshioka

Generalized quantum measurements are an important extension of projective or von Neumann measurements, in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two…

We present strictly efficient schemes for scalable measurement-based quantum computing using continuous-variable systems: These schemes are based on suitable non-Gaussian resource states, ones that can be prepared using interactions of…

Quantum Physics · Physics 2013-05-30 Matthias Ohliger , Jens Eisert

We study sequential measurement scenarios where the system is repeatedly subjected to the same measurement process. We first provide examples of such repeated measurements where further repetitions of the measurement do not increase our…

Quantum Physics · Physics 2016-09-14 Erkka Haapasalo , Teiko Heinosaari , Yui Kuramochi

Absorption measurement is an exceptionally versatile tool for many applications in science and engineering. For absorption measurements using laser beams of light, the sensitivity is theoretically limited by the shot noise due to the…

Optics · Physics 2021-04-22 Fu Li , Tian Li , Marlan O. Scully , Girish S. Agarwal

We describe in a qualitative way a possible picture of the Measurement Process in Quantum Mechanics, which takes into account: 1. the finite and non zero time duration T of the interaction between the observed system and the microscopic…

Quantum Physics · Physics 2018-02-20 Sergio Doplicher

Suppose we are given an entangled pair and then one can ask how well we can produce two entangled pairs starting from a given entangled pair using only local operations. To give response of the above asked question, we study broadcasting of…

Quantum Physics · Physics 2009-11-13 Satyabrata Adhikari , B. S. Choudhury , Indranil Chakrabarty

Unsharp measurements are increasingly important for foundational insights in quantum theory and quantum information applications. Here, we report an experimental implementation of unsharp qubit measurements in a sequential communication…

The quantum no-broadcasting theorem states that it is fundamentally impossible to perfectly replicate an arbitrary quantum state, even if correlations between the copies are allowed. While quantum broadcasting cannot occur through any…

Quantum Physics · Physics 2025-06-25 Yuxuan Zheng , Xinfang Nie , Hongfeng Liu , Yutong Luo , Dawei Lu , Xiangjing Liu

Fault-tolerant quantum computation can be achieved by creating constant-sized, entangled resource states and performing entangling measurements on subsets of their qubits. Linear optical quantum computers can be designed based on this…

Quantum Physics · Physics 2026-02-03 Brendan Pankovich , Alex Neville , Angus Kan , Srikrishna Omkar , Kwok Ho Wan , Kamil Brádler

Measurement based (MB) quantum computation allows for universal quantum computing by measuring individual qubits prepared in entangled multipartite states, known as graph states. Unless corrected for, the randomness of the measurements…

Quantum Physics · Physics 2018-02-28 Rawad Mezher , Joe Ghalbouni , Joseph Dgheim , Damian Markham

In this paper, we establish a general theoretical framework for the description of continuous quantum measurements and the statistics of the results of such measurements. The framework concerns the measurement of an arbitrary quantum system…

Quantum Physics · Physics 2018-04-23 Albert Franquet , Yuli V. Nazarov , Hongduo Wei

In measurement-based quantum computing an algorithm is performed by measurements on highly-entangled resource states. To date, several implementations were demonstrated, all of them assuming perfect noise-free environments. Here we consider…

Monitoring a quantum observable continuously in time produces a stochastic measurement record that noisily tracks the observable. For a classical process such noise may be reduced to recover an average signal by minimizing the mean squared…

Quantum Physics · Physics 2017-12-13 Luis Pedro García-Pintos , Justin Dressel

Quantum channels describe the most general dynamics of open quantum systems. A quantum channel, as a linear map on vectorized quantum states, can be represented by a single matrix, whose spectrum is called the channel spectrum. Here we…

Quantum Physics · Physics 2026-01-28 Yuan-De Jin , Wen-Long Ma

One of the main subjects of this paper is to study quantum property testing with local measurement. In particular, we establish a novel $\ell_2$ norm connection between quantum property testing problems and the corresponding distribution…

Quantum Physics · Physics 2020-01-14 Nengkun Yu

A typical bipartite quantum protocol, such as EPR-steering, relies on two quantum features, entanglement of states and incompatibility of measurements. Noise can delete both of these quantum features. In this work we study the behavior of…

Quantum Physics · Physics 2015-10-14 Teiko Heinosaari , Jukka Kiukas , Daniel Reitzner , Jussi Schultz

Local operations on subsystems and classical communication between parties (LOCC) constitute the most general protocols available on spatially separated quantum systems. Every LOCC protocol implements a separable generalized measurement --…

Quantum Physics · Physics 2014-08-07 Scott M. Cohen

Relativity theory severely restricts the ability to perform nonlocal measurements in quantum mechanics. Studying such nonlocal schemes may thus reveal insights regarding the relations between these two fundamental theories. Therefore, for…