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Using a spontaneous parametric-downconversion source of photon pairs, we are working towards the creation of arbitrary 2-qubit quantum states with high fidelity. Currently, all physically allowable combinations of polarization entanglement…

Quantum Physics · Physics 2007-05-23 Paul Kwiat , Joe Altepeter , David Branning , Evan Jeffrey , Nicholas Peters , Tzu-Chieh Wei

A central requirement in asymmetric quantum nonlocality protocols, such as quantum steering, is the precise reconstruction of state assemblages -- statistical ensembles of quantum states correlated with remote classical signals. Here we…

Characterization of quantum processes is a preliminary step necessary in the development of quantum technology. The conventional method uses standard quantum process tomography, which requires $d^2$ input states and $d^4$ quantum…

Quantum Physics · Physics 2020-02-26 Zhibo Hou , Jun-Feng Tang , Christopher Ferrie , Guo-Yong Xiang , Chuan-Feng Li , Guang-Can Guo

In this work we have explored few tools in Quantum State Tomography for Continuous Variable Systems. The concept of quantum states in phase space representation is introduced in a simple manner by using a few statistical concepts. Unlike…

Quantum Physics · Physics 2019-12-12 Ludmila Botelho

We describe a quantum algorithm to estimate the $\alpha$-Renyi entropy of an unknown density matrix $\rho\in\mathcal{C}^{d\times d}$ for $\alpha\neq 1$ by combining the recent technique of quantum singular value transformations with the…

Quantum Physics · Physics 2021-09-01 Sathyawageeswar Subramanian , Min-Hsiu Hsieh

We establish methods for quantum state tomography based on compressed sensing. These methods are specialized for quantum states that are fairly pure, and they offer a significant performance improvement on large quantum systems. In…

Quantum Physics · Physics 2015-05-14 David Gross , Yi-Kai Liu , Steven T. Flammia , Stephen Becker , Jens Eisert

It is known that the variance and entropy of quantum observables decompose into intrinsically quantum and classical contributions. Here a general method of constructing quantum-classical decompositions of resources such as uncertainty is…

Quantum Physics · Physics 2023-07-07 Michael J. W. Hall

We propose a method to prepare entangled states and implement quantum computation with atoms in optical cavities. The internal state of the atoms are entangled by a measurement of the phase of light transmitted through the cavity. By…

Quantum Physics · Physics 2009-11-10 Anders S. Sorensen , Klaus Molmer

We investigate universal features of measurement-and-feedback control of quantum chaotic dynamics by examining the quantum Arnold cat map, a paradigmatic model of quantum chaos. Inspired by probabilistic control of classical chaos, our…

Quantum Physics · Physics 2026-02-26 Andrew A. Allocca , Devesh K. Verma , Sriram Ganeshan , Justin H. Wilson

Measurements are central in all quantitative sciences, and a fundamental challenge is to make observations without systematic measurement errors. This holds in particular for quantum information processing, where other error sources, such…

Many protocols within quantum cryptography, communications, and computing require the ability to generate entangled states as well as spectral qudits. Nonlinear interferometry is a viable way to engineer these complex quantum states of…

Quantum Physics · Physics 2026-05-19 Cody Charles Payne , Elaganuru Bashaiah , Markus Allgaier

Recently developed quantum algorithms suggest that quantum computers can solve certain problems and perform certain tasks more efficiently than conventional computers. Among other reasons, this is due to the possibility of creating…

Quantum Physics · Physics 2007-05-23 Rolando D. Somma

In this article we develop a continuous variable (CV) shadow tomography scheme with wide ranging applications in quantum optics. Our work is motivated by the increasing experimental and technological relevance of CV systems in quantum…

Quantum Physics · Physics 2024-05-03 Simon Becker , Nilanjana Datta , Ludovico Lami , Cambyse Rouzé

The decay of an unstable system is usually described by an exponential law. Quantum mechanics predicts strong deviations of the survival probability from the exponential: indeed, the decay is initially quadratic, while at very large times…

We introduce novel schemes for quantum computing based on local measurements on entangled resource states. This work elaborates on the framework established in [Phys. Rev. Lett. 98, 220503 (2007), quant-ph/0609149]. Our method makes use of…

Quantum Physics · Physics 2009-11-13 D. Gross , J. Eisert , N. Schuch , D. Perez-Garcia

Shadow tomography is a scalable technique to characterise the quantum state of a quantum computer or quantum simulator. The protocol is based on the transformation of the outcomes of random measurements into the so-called classical shadows,…

Quantum Physics · Physics 2023-10-27 Hai-Chau Nguyen

In the last years the possibility of creating and manipulating quantum states of light has paved the way to the development of new technologies exploiting peculiar properties of quantum states, as quantum information, quantum metrology &…

Quantum Physics · Physics 2016-06-17 Marco Genovese

Extracting tomographic information about quantum states is a crucial task in the quest towards devising high-precision quantum devices. Current schemes typically require measurement devices for tomography that are a priori calibrated to…

Quantum Physics · Physics 2023-07-13 Ingo Roth , Jadwiga Wilkens , Dominik Hangleiter , Jens Eisert

We consider an arbitrary quantum system coupled non perturbatively to a large arbitrary and fully quantum environment. In [G. Ithier and F. Benaych-Georges, Phys. Rev. A 96, 012108 (2017)] the typicality of the dynamics of such an embedded…

Quantum Physics · Physics 2017-12-20 Grégoire Ithier , Saeed Ascroft , Florent Benaych-Georges

Quantum state reconstruction for continuous-variable systems such as the radiation field poses challenges which arise primarily from the large dimensionality of the Hilbert space. Many proposals for state reconstruction exist, ranging from…

Quantum Physics · Physics 2021-12-28 Soumyabrata Paul , S. Lakshmibala , V. Balakrishnan , S. Ramanan